Version 4.6 (2012)

Web Site: www.intermagnet.org

Version 4.6 (2012)

INTERMAGNET TECHNICAL REFERENCE MANUAL

Version 4.62012

Edited by: Benoît St-Louis

This document has been prepared by the INTERMAGNET Operations Committee andExecutive Council. Every effort has been made to ensure that the information is accurateand current. The document is distributed in the hope that it will be a useful reference notonly for those participating formally in INTERMAGNET, but also for the greatergeomagnetic community.

Acknowledgements

We gratefully acknowledge the many and significant contributions and commentsprovided by our colleagues.

This manual is based on the original document (INTERMAGNET Technical ReferenceManual version 1.0 1994 )

Edited by: Douglas F. TriggRichard L. Coles

Prepared by: Diane Regimbald

The INTERMAGNET office:

INTERMAGNETc/o British Geological SurveyMurchison HouseWest Mains RoadEdinburgh EH9 3LAUK

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TABLE OF CONTENTS

QUICK REFERENCES' INTERMAGNET WEB SITE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v' GIN INTERNET ADDRESSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v' DVD/CD-ROM DISTRIBUTION OFFICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v' GENERAL INQUIRIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

CHAPTER 1 INTERMAGNET1.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 INTERMAGNET OBJECTIVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 HISTORY AND STATUS OF INTERMAGNET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 THE INTERMAGNET PRINCIPLES AND CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.5 PARTICIPATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.6 PRODUCTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.7 CONDITIONS OF USE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.8 INTERMAGNET MANAGEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

CHAPTER 2 INTERMAGNET MAGNETIC OBSERVATORIES - IMOs2.1 SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2 DATA SAMPLING AND FILTERING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.3 DATA ENCODING FOR ELECTRONIC MAIL TRANSMISSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.4 DATA ENCODING FOR SATELLITE TRANSMISSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.5 DATA ENCODING FOR DVD/CD-ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.6 ABSOLUTE MEASUREMENTS / BASELINES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

CHAPTER 3 GEOMAGNETIC INFORMATION NODES - GINs3.1 DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.2 FUNCTIONS AND RESPONSIBILITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.3 DATA TRANSMISSION FORMATS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.4 USER ACCESS TO GINs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.5 GIN MANAGER ADDRESSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113.6 GIN INTERNET ADDRESSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

CHAPTER 4 THE INTERMAGNET DVD/CD-ROM4.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.2 GENERAL FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.3 IAF INTERMAGNET ARCHIVE FORMAT (DVD/CD-ROM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.3.1 IAFV2.10 (2010 and after) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.3.2 IAFV2.00 (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144.3.3 IAFV1.10 (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154.3.4 IAFV1.00 (2007 and before) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.4 STORAGE REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.5 INTERMAGNET DVD/CD-ROM DIRECTORY STRUCTURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.6 INTERMAGNET CD-ROM SOFTWARE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

CHAPTER 5 SATELLITES5.1 GEOSTATIONARY SATELLITES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195.2 METEOSAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195.3 GOES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195.4 TRANSMISSION ACCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195.5 SATELLITE OPERATORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.6 SATELLITE SERVICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

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CHAPTER 6 DATA QUALITY CONTROL6.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236.2 THE OBSERVATORY MEASUREMENT PROCESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236.3 COMPUTATION OF BASELINE VALUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246.4 BASELINE ADOPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256.5 THE COMPUTATION OF TOTAL FIELD DIFFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256.6 SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

CHAPTER 7 WORLD WIDE WEB7.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277.2 WEB SITE ADDRESS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

APPENDIX A-1INTERMAGNET TERMINOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

APPENDIX B-1OBSERVATORIES PARTICIPATING IN INTERMAGNET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

APPENDIX B-2PICTORIAL MAP - SATELLITE FOOTPRINTS AND IMOs OPERATING IN 2012 . . . . . . . . . . . . . . . . . 35

APPENDIX C-1IAFV2.10 INTERMAGNET ARCHIVE FORMAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37IAFV2.00 INTERMAGNET ARCHIVE FORMAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38IAFV1.10 INTERMAGNET ARCHIVE FORMAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39IAFV1.00 INTERMAGNET ARCHIVE FORMAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

APPENDIX C-2INTERMAGNET DVD/CD-ROM DIRECTORY STRUCTURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

APPENDIX C-3IYFV1.02 INTERMAGNET DVD/CD-ROM FORMAT FOR YEARMEAN FILE . . . . . . . . . . . . . . . . . . . 43

APPENDIX D-1INTERMAGNET EXECUTIVE COUNCIL ADDRESSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47INTERMAGNET OPERATIONS COMMITTEE ADDRESSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

APPENDIX E-1INTERMAGNET FORMAT IMFV2.83 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

APPENDIX E-2SATELLITE CODING EXAMPLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

APPENDIX E-3IMFV1.23 INTERMAGNET GIN DISSEMINATION FORMAT FOR MINUTE VALUES . . . . . . . . . . . . 63IMFV1.22 INTERMAGNET GIN DISSEMINATION FORMAT FOR MINUTE VALUES . . . . . . . . . . . . 65

APPENDIX E-4IBFV2.00 INTERMAGNET BASELINE FORMAT (2009 and AFTER) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67IBFV1.20 INTERMAGNET BASELINE FORMAT (2008 and BEFORE) . . . . . . . . . . . . . . . . . . . . . . . . . . 69

APPENDIX E-5IAGA2002 INTERMAGNET EXCHANGE FORMAT (Spreadsheet compatible) . . . . . . . . . . . . . . . . . . . . . 71

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APPENDIX F-1FILTER COEFFICIENTS TO PRODUCE ONE MINUTE VALUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

APPENDIX G-1INTERMAGNET MEMBERSHIP APPLICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79INTERMAGNET MEMBERSHIP APPLICATION FORM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81INTERMAGNET INSTRUMENT SPECIFICATION FORM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83A. CONTINUOUSLY RECORDING VECTOR MAGNETOMETER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83B. CONTINUOUSLY RECORDING SCALAR MAGNETOMETER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83C. DATA ACQUISITION SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83D. DATA TRANSMISSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84E. OBSERVATORY BASELINE INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84F. ABSOLUTE INSTRUMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

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QUICK REFERENCES

'''' INTERMAGNET WEB SITE

www.intermagnet.org

'''' GIN INTERNET ADDRESSES

ottgin@geolab.nrcan.gc.capar_gin@ipgp.frgol_gin@ghtmail.cr.usgs.gov e_gin@mail.nmh.ac.ukkyoto-gin@swdcdb.kugi.kyoto-u.ac.jp

'''' DVD/CD-ROM DISTRIBUTION OFFICE

INTERMAGNET DVD/CD-ROM distribution officeObservatoire Magnétique NationalCarrefour des 8 routesF-45340 Chambon la ForêtFRANCETel: 33 (0) 2-38-33-95-00Fax: 33 (0) 2-38-33-95-04Internet: imso@ipgp.fr

'''' GENERAL INQUIRIES

Duff C. StewartINTERMAGNET Operations Committeec/o U.S. Geological SurveyBox 25046 MS 966Denver Federal CenterDenver, Colorado 80225-0046USA

TEL: 44-131-667-1000FAX: 44-131-667-1877INTERNET: c.turbitt@bgs.ac.uk

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CHAPTER 1 INTERMAGNET

1.1 INTRODUCTION

This manual describes the global near-real-timemagnetic observatory network, known asINTERMAGNET. Throughout the document, the term"magnetic observatory" will mean a recording stationwhere absolute measurements of the geomagnetic fieldare made on a regular basis over many years and whichproduces data of the requisite quality for secularvariation studies. The term "near real-time" in thiscontext means that data are supplied for distributionwithin 72 hours of acquisition.

The automation of magnetic observatories in severalcountries, operated remotely by means of telephonecommunications, has demonstrated that data on thedynamic magnetic field of the Earth can be collectedquickly using modern data capture techniques andcommunications systems. It is logical to coordinatenational activities and to extend the use of suchtechniques worldwide. It is now possible to adopt a newstandard for geomagnetic measuring and monitoringequipment and to transfer data rapidly to regionalGeomagnetic Information Nodes (GINs) using satelliteand network communications. These geomagneticinformation nodes collect data from their sector of theglobe for dissemination to the user communities in atimely manner. GINs can, when needed, exchange dataand may also disseminate products such as geomagneticindices and activity models.

A successful pilot scheme operated during 1989,including the UK, USA, and Canada transmitting andreceiving at 12 minute or 1 hour intervals geomagneticdata recorded every minute. As a result of the pilotscheme, the IAGA Executive Committee endorsedINTERMAGNET. The SEDI (Study of the Earth's DeepInterior) Steering Committee has also endorsedINTERMAGNET.

1.2 INTERMAGNET OBJECTIVE

The INTERMAGNET objective is to establish aglobal network of cooperating digital magneticobservatories, adopting modern standard specificationsfor measuring and recording equipment, in order tofacilitate data exchange and the production ofgeomagnetic products in close to real time.

1.3 HISTORY AND STATUS OFINTERMAGNET

The possibility of worldwide data communicationbetween magnetic observatories was first raisedseriously at the Workshop on Magnetic ObservatoryInstruments, held in Ottawa, Canada, in August 1986.Further discussions, particularly between the BritishGeological Survey (BGS) and the US Geological Survey(USGS) took place in May 1987 at the NordicComparison Meeting held at Chambon la Forêt, France.A pilot scheme between BGS and USGS was describedat the sessions of Division V of IAGA during the XIXthGeneral Assembly of IUGG in Vancouver, Canada, inAugust 1987, with the proposal that the geomagneticcommunity should adopt automatic observatories withsatellite communications as its mode of operation for thefuture. INTERMAGNET embodies the proposal toextend worldwide the network of observatoriescommunicating in this way.

At present the observatories shown in Appendix B-1are transmitting through satellites, or daily by computerlink, to GINs. More stations are coming online rapidly.

GINs are now operating in Edinburgh (BGS), Golden(USGS), Kyoto (Kyoto U.), Ottawa (GSC), and Paris(IPGP).

1.4 THE INTERMAGNET PRINCIPLESAND CONDITIONS

INTERMAGNET is operated according to principlesand conditions which are accepted as necessary anddesirable for maintaining a service of rapid magneticobservatory data exchanges for the internationalscientific community and for commercial users.

1. INTERMAGNET is a non-exclusive program ofworldwide data exchange between magneticobservatories.

2. An INTERMAGNET aim is the establishment andmaintenance of observatories in remote areas wherelocal support is lacking.

3. INTERMAGNET encourages the establishment andmaintenance of digital observatories in developingcountries, with the involvement and enhancement oflocal science and technology.

4. Each participating country/institution is expected tobear the costs of its participation inINTERMAGNET.

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5. Data will be transmitted from observatories oroperating institutes to regional geomagneticinformation nodes (GINs) by satellites, computernetworks or by other near real-time means, usingstandard INTERMAGNET formats.

6. Regional geomagnetic information nodes willexchange data and data products globally as rapidlyas appropriate, and will maintain data files for allcontributing observatories for a period commensuratewith the immediate usefulness of the product.

7. The collected data will be made available to thescientific community and to participatingobservatories on media and in formats approved bythe INTERMAGNET Executive Council.

8. All data are supplied on the condition that they arenot used for commercial gain (media, transcriptionand other costs may be charged to the user).

9. The INTERMAGNET Executive Council recognizesthe value to commerce of geomagnetic data andderived products which are available in near realtime, and accepts the right of participatinginstitutions to recover costs for services and to levycharges where possible and as necessary.Participating institutions will undertake to safeguardthe interests of fellow participants, concerning thecommercial usage of their data.

10.Each INTERMAGNET GIN will provide annually toeach participating institution or observatory astatement of data received by the GIN and of its datasupplied by the GIN to users.

11.Participating institutes will co-operate to facilitate theproduction of globally representative data products,such as the official IAGA indices.

12.Participating institutions will agree to submitdefinitive data annually for inclusion on anINTERMAGNET DVD and will receive in returnone copy of the DVD free of charge.

1.5 PARTICIPATION

INTERMAGNET membership is available toinstitutions who wish to operate one or moreINTERMAGNET Magnetic Observatories (IMOs).Members agree to allow distribution of their IMO datain accordance with INTERMAGNET guidelines. Inreturn for participation, Institutional membershipprovides: access to near real-time data from any IMOsfor all members of the Institution; access to the best inmagnetic observatory technologies and assistance inimplementing them and possibilities of discounts onsatellite communications. There are, at present, nomembership fees. An application to become a memberis submitted to the INTERMAGNET office for approvalby the Executive Council, subject to technical evaluationby the Operations Committee. The membershipapplication form is included in Appendix G-1.

Individual researchers may also be granted access toIMO data distributed through GINs. They must apply toan INTERMAGNET GIN and agree to abide by allINTERMAGNET guidelines. They will then be put incontact with the most convenient GIN. Charges foraccess to data may apply.

1.6 PRODUCTS

Minute values of geomagnetic components along withother INTERMAGNET products may be retrieved fromthe web site (http://www.intermagnet.org) under Data.Minute values are kept on-line permanently to allowcomparisons between preliminary and definitive data andto give data sets that can be used to test software thatworks with preliminary data. When available, definitivedata should preferably be used. A DVD (CD-ROMbefore 2006) containing definitive data fromINTERMAGNET observatories is created annually. TheINTERMAGNET DVDs/CD-ROMs are available at nocharge to participating institutes and to bona fidescientists for academic purposes only. Technical helpfor operators of IMOs may also be available by specialarrangements through the INTERMAGNET office.

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1.7 CONDITIONS OF USE

The Geomagnetic data available throughINTERMAGNET are provided for your use (and for theuse of colleagues collaborating on the same project) andare not for sale or distribution by you to third parties,without the express written permission of the Institutethat operates the observatory. Any report or publicationthat makes use of these data should acknowledge thatInstitute as the source. One copy of each report orpublication should be sent to the Institute.

We ask that the data not be used for commercialpurposes, nor in any project in which you, yourorganization, or your collaborators are in a commercialagreement with any third party.

Your e-mail address, which you provide toINTERMAGNET when requesting data, will be given tothe Institute supplying the data so that it may monitor theuse of its data.

By accessing these data you signify your acceptance ofthese terms and conditions. For commercial applicationsof observatory data, please contact the operating Institutedirectly.

INTERMAGNET accepts no liability in respect of loss,damage, injury or other occurrence arising from theprovision of these data.

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1.8 INTERMAGNET MANAGEMENT

The Executive Council establishes policy forINTERMAGNET, deals with questions of internationalparticipation and data exchange, and communicates withnational agencies and international scientific and fundingagencies.

Executive Council membership:

J.J. Love (USA) (Chairman)D. Boteler (Canada)A. Chulliat (France)D.J. Kerridge (UK)

The Operations Committee advises the ExecutiveCouncil on matters relating to magnetic sensors, datacapture and data processing, and on communicationsoptions, protocols, etc. The Operations Committee isalso responsible for establishing and maintainingstandards of operation and uniform data formats andtransmission characteristics which optimize globalexchange.

Operations Committee membership:

C. Blais (Canada)P. Crosthwaite (Australia)S.M. Flower (United Kingdom)H-J. Linthe (Germany)J. Matzka (Denmark)V. Maury (France)M. Nose (Japan)J. Rasson (Belgium) (Chairman)J. Reda (Poland)B.J. St-Louis (Canada)D.C. Stewart (USA)C.W. Turbitt (United Kingdom)

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CHAPTER 2 INTERMAGNET MAGNETIC OBSERVATORIES - IMOs

2.1 SPECIFICATIONS

An INTERMAGNET Magnetic Observatory (IMO) isa magnetic observatory, having full absolute control, thatprovides one minute magnetic field values measured bya vector magnetometer, and an optional scalarmagnetometer, all with a resolution of 0.1 nT. Vectormeasurements performed by a magnetometer mustinclude the best available baseline referencemeasurement.

An IMO must try to meet the followingrecommendations:

Definitive Data

Accuracy: ±5 nT

Absolute Measurements (See Section 2.6)

Vector Magnetometer

Resolution: 0.1 nTDynamic Range: 8000 nT High Latitude

6000 nT Mid/Equatorial LatitudeBand pass: D.C. to 0.1 Hz Sampling rate: 1 Hz Thermal stability: 0.25 nT/ECLong term stability: 5 nT/year

Scalar Magnetometer

Resolution: 0.1 nTAccuracy: 1 nTSampling rate: 0.033 Hz (30 sec)

Clock Timekeeping

Observatory data logger: 5 seconds/monthData collection platform: ± 1.5 sec GOES, GMS

± 1.0 sec METEOSAT

Recorder

An on-site recorder is necessary so data are not lost as aresult of satellite transmission outages.

Transmission

Transmission must be by satellite or other electronicmeans, within 72 hours of acquisition, to a GeomagneticInformation Node (GIN).

Note: Keeping within the time slot for satellitetransmission is an important duty of an IMO operator.When advised by a GIN of a time drift, the IMOoperator must make the necessary corrections within 24hours.

Other

Data format: IAGA2002 or IMFV2.83 orIMFV1.23 (or later)

Definitive data: to be submitted for inclusion onthe DVD/CD-ROM

Baseline data: each component to be submittedfor inclusion on the DVD/CD-ROM

Filtering: to INTERMAGNET standard (Section 2.2)

Proton Gyromagnetic Ratio

In 2009, INTERMAGNET adopted the new protongyromagnetic ratio published by the CODATA group in2006: gp = 2.675153362*108 T-1s-11

2.2 DATA SAMPLING AND FILTERING

In its Resolution 12 from the 1979 Assembly inCanberra, IAGA noted the desirability of digitalmagnetic observatories using a sampling rate no slowerthan once every 10 seconds. In that resolution, IAGAalso stated that the one-minute means should be centeredon the minute.

To minimize aliasing of higher frequency signals intothe pass-band of the final minute data series, anti-aliasing filters should be included in the analogueportions of magnetometers before analogue-to-digitalconversion. The filter responses should be matched tothe chosen primary digital sampling rate. Subsequent tothe digital sampling, INTERMAGNET requires that anumerical filter be applied in order to obtain the finalminute data series.

One digital filter that is widely used byINTERMAGNET can be achieved by applying thefollowing coefficients (for a Gaussian filter) to a seriesof 19 samples of 5-second data:C0 = 0.00229315 C10 = 0.11972085C1 = 0.00531440 C11 = 0.10321785C2 = 0.01115655 C12 = 0.08061140C3 = 0.02121585 C13 = 0.05702885C4 = 0.03654680 C14 = 0.03654680C5 = 0.05702885 C15 = 0.02121585C6 = 0.08061140 C16 = 0.01115655C7 = 0.10321785 C17 = 0.00531440C8 = 0.11972085 C18 = 0.00229315C9 = 0.12578865

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For a filter output value to be centered on the minute,coefficient C0 is applied 45 seconds before this minuteand coefficient C18 is applied 45 seconds after theminute.

In addition to the attenuation provided by thenumerical filter, a “natural filter” applies, estimated at -9to -18 dB/Octave typically, caused by the decrease inenergy of the natural field with increasing frequency.

Examples of other acceptable sets of filtercoefficients, for use with various sampling rates ofproperly anti-aliased signals are presented in AppendixF-1.

A scalar magnetometer must provide a samplecentered on the same time as the output of the digitalfilter used with the vector magnetometer.

When mean values are to be calculated the question ofhow to handle missing data arises. For a number ofreasons it is difficult to devise a simple objective rulethat can be applied to all cases. INTERMAGNETrecommends a simple and pragmatic approach; meanvalues may be calculated when 90% or more of thevalues required for calculation of the mean are available.When fewer than 90% of the required values areavailable the mean value should be assigned the valueused to flag missing data. INTERMAGNETrecommends adoption of this rule for both simple meanand weighted mean calculations. For example, a simplehourly mean value may be computed when 54 or moreone-minute values are available for the hour. Similarly,if a one-minute value is constructed from one-secondsamples, the one-minute value may be computed when54 or more one-second samples are available. In thiscase the weights (filter coefficients) assigned to thesamples must be re-normalized (the sum of the weightsapplied to the samples used to calculate the mean valuemust be unity). INTERMAGNET observatories areexpected to provide high levels of data continuity, so thisrule is expected to be applied only rarely.

2.3 DATA ENCODING FOR ELECTRONICMAIL TRANSMISSION

Electronic mail transmission of data to a GIN must bedone using IAGA 2002 Format or INTERMAGNETGIN Dissemination Format for Minute ValuesIMFV1.23 described in Appendix E-3. When an IAGA2002 file is sent, the SUBJECT field should contain thecorrectly formatted IAGA 2002 file name. When usingthe IMFV1.23 Format, the SUBJECT field of theelectronic mail header should contain the filename beingsent as defined in IMFV1.23.

for example:

Subject:MAR1592.BOU

This indicates that a day file containing data fromBoulder observatory March 15 is sent. A complete day'sdata is assembled into each IMFV1.23 file.

A list of GIN Internet addresses can be found in theQuick References section.

2.4 DATA ENCODING FOR SATELLITETRANSMISSION

In preparation for transmitting data to one of severalpossible satellites an IMO will first prepare its data inINTERMAGNET format IMFV2.83 or later, which isfully described in Appendix E-1. This format imposesa common structure on the data files, ensuring that allnecessary information is included so that the data may beproperly decoded at a GIN. Once data are in IMFV2.83,a supplementary encoding step is applied to make thedata stream, as transmitted to satellites, exactlycompatible with the requirements of the satelliteoperators. Appendix E-2 shows the supplementaryencoding steps for the GOES and Meteosat satellitesalong with examples using a specific data set. AppendixE-2 also provides provisional information aboutencoding for the GMS satellite.

2.5 DATA ENCODING FOR DVD/CD-ROM

Definitive data for an IMO are to be provided toINTERMAGNET shortly after the end of each calendaryear (six months maximum) for inclusion in an annualINTERMAGNET DVD. The format for submission ofdata appears in Appendix C-1. Baseline data willaccompany the definitive data, and will be provided informat IBFV2.00 or later as described in Appendix E-4.Refer to chapter 4 for a general description of theDVD/CD-ROM.

2.6 ABSOLUTE MEASUREMENTS /BASELINES

The provision of absolute control at a magneticobservatory requires a series of measurements of theabsolute values of the geomagnetic field using manuallyoperated instruments. Ideally, the frequency at whichthese measurements are made may vary from daily toweekly, depending on the variometer characteristics, thestability of the piers and installation and logisticalconsiderations. The quality of the absolute control maybe judged by examining the baseline corrections to thevariometer data (see Appendix E-4). Some IMOs mayuse intermediate Reference Measurements (RM) whichare more stable for inter-comparison. Chapter 6

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provides a discussion of data quality control.

Several combinations of instrumentation are in use forabsolute determinations, but INTERMAGNETrecommends a proton precession magnetometer and aDeclination/Inclination magnetometer (fluxgate mountedon a theodolite). Many factors are involved in achievinggood baselines at a magnetic observatory. Somesuggestions are presented in this short summary. A goodadopted baseline shows a low scatter of individualbaseline determinations, and has few drifts or offsets.Executive Council and Operations Committeerecommend to:

1. Make weekly absolute observations, avoidingintervals of magnetic disturbance. If the baseline ischanging rapidly, increase the frequency of absoluteobservations.

2. Make regular physical inspections of all observatorybuildings to ensure that no magnetic materialswhich would cause jumps in baselines have beenlying around, inside or outside the building.

3. Ensure that absolute instruments and theirsupporting piers are free from contaminatingmagnetic materials.

4. Set up a pier in an undisturbed area outside theabsolute building; determine the absolutedifferences between the external pier and the mainabsolute pier at least once a year, to check forchanges in the magnetic environment.

5. Maintain an up-to-date diary of absolutemeasurements, visits, repairs and other actions at theobservatory.

6. Operate two variometers at the observatory andcompare their data records.

7. Keep variometers, interconnecting cables, andcontrol electronics at constant temperatures.

8. Continuously monitor and record the temperaturesof all sensors, cables, and electronics units.

9. Review the procedures in use for absolutemeasurements at the observatory and consider ifthere are better procedures that could be use.INTERMAGNET recommends the use of a protonp r e c e s s i o n m a g n e t o m e t e r a n d aDeclination/Inclination magnetometer (fluxgatemounted on a theodolite).

10. Undertake visits between institutions by observers

to encourage the exchange of ideas oninstrumentation and observatory practice. AttendIAGA workshops.

11. Establish inter-observatory absolute instrumentcomparisons by observers, similar to the concept ofthe Scandinavian inter-observatory comparisons.Attend IAGA workshops.

12. Undertake better training of observers.

13. Provide meaningful information to observers abouthow their work contributes to local and worldwideresearch projects, and how baseline quality canaffect the research.

This manual will not elaborate on the details ofabsolute techniques. However, useful articles can befound in Wienert (1970), Stuart (1984), Coles (1988),Kauristie et al. (1990), Rasson (1996), and Best andLinthe (1998). Two comprehensive manuals containdetailed sections on absolute measurement techniques.These are the "Guide for Magnetic Repeat StationSurveys" (Newitt, Barton, and Bitterly) and the "Guidefor Magnetic Measurements and Observatory Practice"(Jankowski and Sucksdorff).

References:

Best, A. and Linthe, H.-J. (eds.) 1998. Proceedings ofthe VIIth Workshop on Geomagnetic ObservatoryInstruments, Data Acquisition and Processing,GeoForschungsZentrum Potsdam, Scientific TechnicalReport STR98/21, 450p.

Coles, R.L. (ed.) 1988. Proceedings of the InternationalWorkshop on Magnetic Observatory Instruments;Geological Survey of Canada Paper 88-17, 94 p.

Jankowski, J. and Sucksdorff, C. 1996. Manual onMagnetic Measurements and Observatory Practice,International Association of Geomagnetism andAeronomy, Boulder, Co., 235 p.

Kauristie, K., Sucksdorff, C., and Nevanlinna, H. (eds.)1990. Proceedings of the International Workshop onGeomagnetic Observatory Data Acquisition andProcessing; Finnish Meteorological Institute,Geophysical Publications No.15, 151 p.

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Loubser, L. 2002. Proceedings of the Xth IAGAWorkshop on Geomagnetic Instruments, DataAcquisition and Processing, 300 p.

Newitt, L.R., Barton, C.E., and Bitterly, J. 1996. Guidefor Magnetic Repeat Station Surveys, InternationalAssociation of Geomagnetism and Aeronomie, Boulder,Co., 112 p.

Prigancová, A., Vörös, Z., 2000. IXth IAGA Workshopon Geomagnetic Observatory Instruments, DataAcquisition and Processing, Contributions to Geophysicsand Geodesy, Geophysical Institute Slovak Academy ofSciences Vol. 31, No. 1, 454 p.

Rasson, J.L. (ed.) 1996. Proceedings of the VIthWorkshop on Geomagnetic Observatory Instruments,Data Acquisition and Processing, Dourbes, InstitutRoyal Meteorologique de Belgique, Publicationscientifique et technique N. 003., 249 p.

Stuart, W.F.(ed.) 1984. Geomagnetic observatory andsurvey practice; reprinted from Geophysical Surveys,Vol. 6, nos. 3/4; D. Reidel, Dordrecht/Boston, 464 p.

Wienert, K.A. 1970. Notes on geomagnetic observatoryand survey practice; UNESCO, Paris, 217 p.

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CHAPTER 3 GEOMAGNETIC INFORMATION NODES - GINs

3.1 DEFINITION

In order that all INTERMAGNET data transfers maybe handled efficiently, INTERMAGNET has establisheda number of Geomagnetic Information Nodes (GINs).The function of the GINs is to collect magneticobservatory data in near-real time, store it in a database,and forward it to the INTERMAGNET data repositoryfrom which it may be easily obtained through the website by users of INTERMAGNET data. The GINmanager functions as a point of contact for IMOs toresolve any data transmission and formatting problems.

Geomagnetic Information Nodes have been set up inthe following locations:

Golden, Colorado - United States GeologicalSurvey

Ottawa, Canada - Geological Survey ofCanada

Edinburgh, Scotland - British Geological SurveyParis, France - Institut de Physique du

Globe de ParisKyoto, Japan - Kyoto University

Full GIN addresses are given at the end of thischapter. All sites are either equipped with satellitereceiving equipment or receive satellite data from asatellite collecting center. All sites also have computerssupporting electronic mail. This allows easy input ofdata from any magnetic observatory participating inINTERMAGNET. Depending on GIN location and themethod used to input data, either satellite or electronicmail, observatory data are available to users from aminimum time of 12 minutes to a maximum time of 72hours after the observatory recordings are made. If theobservatory is transmitting its data through the GOESsatellite links, the data reach the GIN within 12 minutesof recording. An alternative method, for observatoriesnot equipped with satellite transmission equipment, is toinput data to a GIN using electronic mail (E-Mail). Touse this method an observatory must relay its data atleast once every 72 hours to a GIN.

3.2 FUNCTIONS AND RESPONSIBILITIES

When observatory data are relayed to a GIN theformat of these data may be either IAGA 2002,I N T E R M A G N E T F o r ma t I M F V 2 . 8 3 o rINTERMAGNET GIN Dissemination Format forMinute Values IMFV1.23, or subsequent versions. TheIMFV2.83 format is used for data transmitted through asatellite link, the IAGA 2002 and IMFV1.23 format for

data input via an E-Mail message.Once the data have been received the first process

carried out by the GIN is to convert the IMFV2.83format data to IMF V1.23 format and to designate themas REPORTED data. The second process is to forwardthese data files onto the INTERMAGNET datarepository.

Each GIN will, as a routine daily task, producestackplots of data received from all input sources. Theseare used as a quality assurance guide on the operation ofeach contributing observatory. No attempt will be madeat any GIN to modify any REPORTED data input to it,but a GIN may apply spike removal routines toREPORTED data to produce other files from whichstackplots are produced.

IMFV1.23 data can exist in one of three forms:

1) REPORTED Data - Data as input from anobservatory, transmitting through a satellite or using E-Mail. REPORTED data have not had any baselinecorrections applied, they may contain spikes and mayhave missing values.

2) ADJUSTED Data - Each observatory or its parentinstitute is allowed to modify REPORTED data files toproduce ADJUSTED data, with a goal of 7 days aftertransmission. These adjustments may be to modifybaselines, remove spikes or fill gaps, etc. on any day file.When data are missing from an ADJUSTED data file,these data may be input to a GIN in a later message.This new message file can be transmitted to a GIN withthe 'A' flag set in byte 25 of each hourly block header.ADJUSTED data are maintained online until the annualDVD is available. They are then archived by the GINand are only available thereafter by special arrangement.

3) DEFINITIVE Data - This describes observatory datawhich have been corrected for baseline variations, havehad spikes removed and gaps filled where possible.DEFINITIVE data have each block header byte 25 informat IMFV1.23 set to 'D', and the quality of the data issuch that in this form they would be used for inclusioninto Observatory Year Books, input to World DataCenters and included on the annual INTERMAGNETDVD.

3.3 DATA TRANSMISSION FORMATS

In order that all INTERMAGNET data relayedbetween GINs and participating institutes share commonstandards, a series of GIN data formats have been

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developed by the INTERMAGNET OperationsCommittee. All data transfers between GINs and IMOsare in these formats, and a GIN will not accept data fromany INTERMAGNET participant unless they adherestrictly to the defined formats.

1) IAGA 2002 or IMFV1.23 INTERMAGNETGIN DISSEMINATION FORMAT FORMINUTE VALUES

These define the formats in which observatory minutedata may be input to a GIN by electronic mail. Theseformats are fully defined and described in Appendix E-3and Appendix E-5.

2) INTERMAGNET GIN FORMAT FORMAGNETIC INDICES

Details of this format have yet to be formulated by theINTERMAGNET Operations Committee. Anaddendum to this manual will be prepared when thisformat has been defined.

3.4 USER ACCESS TO GINs

GINs are responsible for data from the observatorieslisted in Appendix B-2. User access to the GINs islimited to the observatories who send their data to agiven GIN. The access method is established separatelyby each GIN.

The complete INTERMAGNET data set for allparticipating observatories is very large. The entire database is located on the primary INTERMAGNET webserver.

Public access to INTERMAGNET data is providedthrough the INTERMAGNET web site only. SeeChapter 7 for more information on INTERMAGNET'sweb sites and data.

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3.5 GIN MANAGER ADDRESSES

Any enquiries to individual GINs should be made tothe INTERMAGNET GIN Manager at the followingaddresses:

USGS - USA:Duff C. StewartU.S. Geological SurveyBox 25046 MS 966Denver Federal CenterDenver, Colorado 80225-0046USATelephone: 1-303-273-8485Fax: 1-303-273-8506Internet: gol_manager@ghtmail.cr.usgs.gov

GSC - Canada:David CalpGeological Survey of CanadaGeophysics Division7 Observatory CrescentOttawa, OntarioCANADAK1A 0Y3Telephone: 1-613-837-1757Fax: 1-613-824-9803Internet: ottmanager@geolab.nrcan.gc.ca

BGS - Scotland:Simon M. FlowerGeomagnetism TeamBritish Geological SurveyMurchison HouseWest Mains RoadEdinburgh EH9 3LAUKTelephone: 44-131-667-1000Fax: 44-131-667-1877Internet: e_ginman@mail.nmh.ac.uk

IPG - France:Virginie MauryInstitut de Physique du Globe de ParisObservatoires magnétiques - Bureau 1101, rue Jussieu75238 Paris Cedex 05FRANCETelephone: 33 (0) 1-83-95-77-80Fax: 33 (0) 1-71-93-77-09Internet: p_ginman@ipgp.fr

Kyoto University - Japan:Masahito NoséData Analysis Center for Geomagnetism and Space MagnetismGraduate School of Science, Bldg #4Kyoto UniversityOiwake-cho, Kitashirakawa, Sakyo-kuKyoto 606-8502JAPANTelephone: 81-75-753-3959Fax: 81-75-722-7884Internet: imagmanager@swdcdb.kugi.kyoto-u.ac.jp

3.6 GIN INTERNET ADDRESSES

ottgin@geolab.nrcan.gc.capar_gin@ipgp.frgol_gin@ghtmail.cr.usgs.gov e_gin@mail.nmh.ac.ukkyoto-gin@swdcdb.kugi.kyoto-u.ac.jp

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CHAPTER 4 THE INTERMAGNET DVD/CD-ROM

4.1 INTRODUCTION

In January 1992 the Executive Council and OperationsCommittee decided to produce a CD-ROM of definitiveminute data values from observatories of participatinginstitutions, beginning with 1991 data and continuingannually thereafter. Users thus have access to globalmagnetic observatory data near-real time values and alsothe final, definitive data. Within six months after the endof the year the institution responsible for an IMO mustdeliver a complete set of definitive data (after de-spiking,padding of missing values, application of correctedbaselines and other processing procedures) and samplesof baseline data to be included on the annualINTERMAGNET DVD/CD-ROM.

The INTERMAGNET DVD/CD-ROM only containsdata from participating observatories. Participatingobservatories are those that meet the INTERMAGNETstandards and also report their data to a GIN within 72hours of recording. The data from all contributingobservatories were provided by the institutionsresponsible for those observatories.

4.2 GENERAL FEATURES

The first INTERMAGNET CD-ROM contains datafrom 41 observatories provided by 11 countries for theyear 1991. These countries are Australia, Canada,Denmark, Finland, France, Hungary, Japan, Russia,Sweden, the United Kingdom, and the United States.The 1992 and later DVD/CD-ROMs also containbaseline data for the year for each observatory in theform of text and plots. Appendix B-1 of this manualprovides a list of observatories currently contributing tothe DVD, and Appendix B-2 gives a map showing theirlocations.

The DVD/CD-ROM itself conforms to the ISO 9660standards, and only requires a DVD/CD-ROM readerwith drive extensions that meet these standards to beoperational. However, the access software (see below)requires several basic items, which include:1. An IBM PC/AT or compatible microcomputer.2. 640 Kilobytes (Kb) of memory.3. MS-DOS or PC-DOS, version 3.1 or higher operating

system.4. Video Graphics Adapter (VGA) with at least 256 Kb

of graphics memory.5. An optional Epson-compatible dot matrix, or

Hewlett-Packard Laserjet-compatible laser printer.

4.3 IAF INTERMAGNET ARCHIVEFORMAT (DVD/CD-ROM)

INTERMAGNET has published CDs and DVDs ofgeomagnetic observatory data since 1991. The CDs andDVDs contain a variety of metadata, including contactinformation and quality control records. Thegeomagnetic data on the CDs and DVDs is held inINTERMAGNET archive format. This format holdsminute, hourly and daily mean values as well as Kindices.

The data are coded as 32-bit (long integer) binarywords, with 5888 words comprising a day-long record.Each file contains one month of day-records (so files arevariable length, from 28 to 31 records). Each day ofdata has a header and data section, the data beingsubdivided into minute means, hourly means, dailymeans and a set of K-indices. To date, four versions ofthis format have been used: IAFV1.00 being the originaldescription of the format. It was only designated asversion 1.00 in 2007. Minor undocumented changeswere made to how the header was used over the lifetimeof this version. IAFV1.10 was defined in 2008 to addthe publication date, encoding of the format versionnumber and to reserve word 16 in the header, affectingwords 14, 15 and 16. In 2009, delta-F was introduced inIAFV2.00 affecting words 6,8 and 15 in the header, andwords 4337 to 5776, words 5849 to 5872 and word 5876in the data section. Also in IAFV2.00, space paddingwas specified to be at the left most position affectingword 13 in the header and words 5885 to 5888 in thedata section were made available for each contributinginstitution. In 2010, IAFV2.10 was defined to allow fora missing instrument designator affecting words 6 and15 in the header, and words 4337 to 5776 in the datasection. Appendix C-1 provides a schematicrepresentation of the record structure.

4.3.1 IAFV2.10 (2010 and after)

Words 1 to 16 comprise the header section containinga mixture of text and numeric fields, including a 3-letterobservatory identification preceded with a space [hex20](ID) code, the year concatenated with the day of theyear, co-latitude, longitude, elevation, reportedorientation, originating organization, a D-conversionfactor, data quality, instrumentation, K-9, sampling rate,sensor orientation, publication date and format version.From 2010 onward, the orientation codes "XYZ" and"HDZ" have been added to "XYZG" and "HDZG"where "G" represents ∆F (see description below). Thesenew codes indicate that the observatory is recording 3

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elements only (no scalar instrument). The D-conversionfactor is a fixed value used only in the graphics portionof the access software to allow Declination to be plottedin minutes of arc and equivalent nanoteslas (nT). It isgiven as H/3438*10000, where H is the annual meanvalue of the horizontal intensity. Example: If H is 16500D will be 47993(Integer). When XYZG or XYZ is used,the D-conversion factor should be set to 10000.

ASCII values, such as the observatory ID andorientation, are also stored as 32-bit words, but are codedas the hexadecimal byte-string corresponding to theASCII string. For example, the string "HDZF" is codedas the sequence "48 44 5A 46". Where a string is shorterthan four bytes, it is padded to the left with spaces. Forexample, the string "ESK" is coded as the sequence "2045 53 4B".

Word 11 is the K-9 value for the observatory in nT,word 12 is the digital sampling rate in msec, and word 13is the sensor orientation. Sensor orientation could beXYZF, DIF, UVZ, HDZ, HDZF etc. and shouldindicates which components are actually measured. If athree component sensor orientation is used, a space mustbe added to the left. Word 14 is the publication dateencoded as 4 ASCII bytes "YYMM" provided byINTERMAGNET. The high byte (left most) of word 15is the INTERMAGNET Archive Format version numbercode provided by the IMO. It takes the form of a binarysingle byte number ranging from 0 to 255. Zero (0x00)represents version 1.00, one (0x01) represents version1.10, two (0x02) represents version 2.00 and three(0x03) represents version 2.10. The other three bytes ofword 15 are reserved for future use and padded withzeros. Word 16 is reserved for future use.

Words 17-5776 contain the minute values of the 4geomagnetic elements (successively X,Y,Z,G orH,D,Z,G or X,Y,Z, or H,D,Z ) for the day. From 2009onward, the 4th element contains the difference betweenthe square root of the sum of the squares of thevariometer components, F(v), and the total field from anindependent scalar recording, F(s). This difference, ∆F,is defined as F(v) - F(s). Both F(v) and F(s) must becorrected to the location in the observatory whereabsolute geomagnetic observations are made. When F(s)is missing or both F(s) and F(v) are missing, ∆F must beset to 999999. When F(v) only is missing, ∆F must beset to -F(s). The values of the 4 elements are stored intenth-units with an implied decimal point. Thus, an Hvalue of 21305.6 is stored (in tenth-nT) as 213056 witha decimal point implied between the last and next-to-lastdigits. Words 5777-5872 are used for the hourly meanvalues of the successive 4 elements. From 2009 onward,words 5849-5872 always record 999999 (missing value),this is done because the 4th element in the data is aquality check for minute mean data and this qualitycheck is meaningless for hourly means. Words 5873-5876 store the 4 daily mean values. From 2009 onward,

word 5876 always record 999999 (missing value)because the quality check for daily means is alsomeaningless. From 2009 onward, the last 4 words(5885-5888) are available for each contributinginstitution. Missing data for minute, hour, and dayvalues are stored as "999999". From 2010 onward, if ascalar instrument is not used (so no data is recorded inthe fourth element) the value "888888" should be usedinstead of "999999". Missing K-Index values are storedas "999".

4.3.2 IAFV2.00 (2009)

Words 1 to 16 comprise the header section containinga mixture of text and numeric fields, including a 3-letterobservatory identification preceded with a space [hex20](ID) code, the year concatenated with the day of theyear, co-latitude, longitude, elevation, reportedorientation, originating organization, a D-conversionfactor, data quality, instrumentation, K-9, sampling rate,sensor orientation, publication date and format version.From 2009 onward, the orientation must be "XYZG" or"HDZG" where "G" represents ∆F (see descriptionbelow). The D-conversion factor is a fixed value usedonly in the graphics portion of the access software toallow Declination to be plotted in minutes of arc andequivalent nanoteslas (nT). It is given asH/3438*10000, where H is the annual mean value of thehorizontal intensity. Example: If H is 16500 D will be47993(Integer). When XYZG is used, the D-conversionfactor should be set to 10000.

ASCII values, such as the observatory ID andorientation, are also stored as 32-bit words, but arecoded as the hexadecimal byte-string corresponding tothe ASCII string. For example, the string "HDZF" iscoded as the sequence "48 44 5A 46". Where a string isshorter than four bytes, it is padded to the left withspaces. For example, the string "ESK" is coded as thesequence "20 45 53 4B".

Word 11 is the K-9 value for the observatory in nT,word 12 is the digital sampling rate in msec, and word13 is the sensor orientation. Sensor orientation could beXYZF, DIF, UVZ, HDZ, HDZF etc. and shouldindicates which components are actually measured. If athree component sensor orientation is used, a space mustbe added to the left. Word 14 is the publication dateencoded as 4 ASCII bytes "YYMM" provided byINTERMAGNET. The high byte (left most) of word 15is the INTERMAGNET Archive Format version numbercode provided by INTERMAGNET. It takes the form ofa binary single byte number ranging from 0 to 255. Zero(0x00) represents version 1.00, one (0x01) representsversion 1.10 and two (0x02) represents version 2.00.The other three bytes of word 15 are reserved for futureuse and padded with zeros. Word 16 is reserved for

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future use.Words 17-5776 contain the minute values of the 4

geomagnetic elements (successively X,Y,Z,G orH,D,Z,G ) for the day. From 2009 onward, the 4thelement contains the difference between the square rootof the sum of the squares of the variometer components,F(v), and the total field from an independent scalarrecording, F(s). This difference, ∆F, is defined as F(v) -F(s). Both F(v) and F(s) must be corrected to the locationin the observatory where absolute geomagneticobservations are made. When F(s) is missing or bothF(s) and F(v) are missing, ∆F must be set to 999999.When F(v) only is missing, ∆F must be set to -F(s). Thevalues of the 4 elements are stored in tenth-units with animplied decimal point. Thus, an H value of 21305.6 isstored (in tenth-nT) as 213056 with a decimal pointimplied between the last and next-to-last digits. Words5777-5872 are used for the hourly mean values of thesuccessive 4 elements. From 2009 onward, words 5849-5872 always record 999999 (missing value), this is donebecause the 4th element in the data is a quality check forminute mean data and this quality check is meaninglessfor hourly means. Words 5873-5876 store the 4 dailymean values. From 2009 onward, word 5876 alwaysrecord 999999 (missing value) because the quality checkfor daily means is also meaningless. From 2009 onward,the last 4 words (5885-5888) are available for eachcontributing institution. Missing data for minute, hour,and day values are stored as "999999". Missing K-Indexvalues are stored as "999".

4.3.3 IAFV1.10 (2008)

Words 1 to 16 comprise the header section containinga mixture of text and numeric fields, including a 3-letterobservatory identification preceded with a space [hex20](ID) code, the year concatenated with the day of the year,co-latitude, longitude, elevation, reported orientation,originating organization, a D-conversion factor, dataquality, instrumentation, K-9, sampling rate, sensororientation, publication date and format version. Theorientation must be "XYZF" or "HDZF". If the Felement is not measured, it must be filled with 999999 inthe data section. The D-conversion factor is a fixedvalue used only in the graphics portion of the accesssoftware to allow Declination to be plotted in minutes ofarc and equivalent nanoteslas (nT). It is given asH/3438*10000, where H is the annual mean value of thehorizontal intensity. Example: If H is 16500 D will be47993(Integer). When XYZF is used, the D-conversionfactor should be set to 10000.

ASCII values, such as the observatory ID andorientation, are also stored as 32-bit words, but are codedas the hexadecimal byte-string corresponding to theASCII string. For example, the string "HDZF" is coded

as the sequence "48 44 5A 46".Word 11 is the K-9 value for the observatory in nT,

word 12 is the digital sampling rate in msec, and word13 is the sensor orientation. Sensor orientation could beXYZF, DIF, UVZ, HDZ, HDZF etc. and shouldindicates which components are actually measured. If athree component sensor orientation is used, a space mustbe added at the end. Word 14 is the publication dateencoded as 4 ASCII bytes "YYMM" provided byINTERMAGNET. The high byte (left most) of word 15is the INTERMAGNET Archive Format version numbercode provided by INTERMAGNET. It takes the form ofa binary single byte number ranging from 0 to 255. Zero(0x00) represents version 1.00 and one (0x01) representsversion 1.10. The other three bytes of word 15 arereserved for future use and padded with zeros. Word 16is reserved for future use.

Words 17-5776 contain the minute values of the 4components (successively X,Y,Z,F or H,D,Z,F) for theday. The 4th component "F" should be included only ifit is measured from a scalar instrument independent ofthe other 3 components otherwise it must be filled with999999. The values of the 4 components are stored intenth-units with an implied decimal point. Thus, an Hvalue of 21305.6 is stored (in tenth-nT) as 213056 witha decimal point implied between the last and next-to-lastdigits and a D value of 527.6 is stored (in tenth-minutes)as 5276 also with a decimal point implied between thelast and next-to-last digits. Words 5777-5872 are usedfor the hourly mean values of the successive 4components. Words 5873-5876 store the 4 daily meanvalues. Words 5877-5884 contain the K-Index*10. Thelast 4 words (5885-5888) are reserved for future use andpadded with zeros. Missing data for minute, hour, andday values are stored as "999999". Missing K-Index andAk values are stored as "999".

4.3.4 IAFV1.00 (2007 and before)

Words 1 to 16 comprise the header section containinga mixture of text and numeric fields, including a 3-letterobservatory identification preceded with a space [hex20](ID) code, the year concatenated with the day of theyear, co-latitude, longitude, elevation, reportedorientation, originating organization, a D-conversionfactor, data quality, instrumentation, K-9, sampling rateand sensor orientation. From 1991 to 2005, the fourthcomponent is the total field from either a scalar(independent) instrument or the total field calculatedf rom the main observatory instrument.INTERMAGNET has a list of which observatoriessupplied which type of total field value between 1991and 2005 and this list is available as a spreadsheet in thearchive viewer software. The D-conversion factor is afixed value used only in the graphics portion of the

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access software to allow Declination to be plotted inminutes of arc and equivalent nanoteslas (nT). It isgiven as H/3438*10000, where H is the annual meanvalue of the horizontal intensity. Example: If H is 16500D will be 47993(Integer). This conversion factor onlyapplies to HDZ observatory data supplied before 2005.

ASCII values, such as the observatory ID andorientation, are also stored as 32-bit words, but are codedas the hexadecimal byte-string corresponding to theASCII string. For example, the string "HDZF" is codedas the sequence "48 44 5A 46".

Word 11 is the K-9 value for the observatory in nT,word 12 is the digital sampling rate in msec, and word 13is the sensor orientation. Sensor orientation could beXYZF, DIF, UVZ, HDZ, HDZF etc. and shouldindicates which components are actually measured. If athree component sensor orientation is used, a space mustbe added at the end. Word 14-15 are reserved for futureuse and padded with zeros. In version 1.10 and later,word 15 have been defined to represent the versionnumber. Previously, it should have been coded to zeroby IMOs, that is the reason this word was chosen for theversion number (zero represents version 1.00). Word 16is set aside for each contributing institution to use as theywish, provided it is coded as a 32-bit binary value.

Words 17-5776 contain the minute values of the 4components (successively X,Y,Z,F or H,D,Z,F) for theday. Until 2005, the 4th component could contain "F"from either a scalar or calculated from the vectorinstrument. From 2006 onward, the 4th componentcontains "F" only if it is measured from a scalarinstrument independent of the other 3 componentsotherwise it must be filled with 999999. The values ofthe 4 components are stored in tenth-units with animplied decimal point. Thus, an H value of 21305.6 isstored (in tenth-nT) as 213056 with a decimal pointimplied between the last and next-to-last digits and a Dvalue of 527.6 is stored (in tenth-minutes) as 5276 also*with a decimal point implied between the last and next-to-last digits. Words 5777-5872 are used for the hourlymean values of the successive 4 components. Words5873-5876 store the 4 daily mean values. Prior to the1994 CD-ROM, words 5877-5884 held the 8(K-Index*10) values for the day. The true IAGAK-Index could be obtained from these K-Index*10values by truncating the second (least significant) digit.From 1994 onward, words 5877-5884 contain theK-Index*10. Until 1998, word 5885 contained theequivalent daily amplitude index (Ak). From 1999onward, word 5885 is reserved for future use and paddedwith zeros. The last 3 words (5886-5888) are reservedfor future use and padded with zeros. Missing data forminute, hour, and day values are stored as "999999".Missing K-Index and Ak values are stored as "999".

4.4 STORAGE REQUIREMENTS

Each 1-day record requires 23,552 bytes, so a month-file for January would require 730,112 bytes of storage.A year of observatory data requires almost 8.6Megabytes (Mb) of storage. The storage capacity of aCD-ROM is about 640 Mb. A single sided, single layerDVD holds about 4.7 Gb, a single sided, double layerDVD about 8.5Gb.

4.5 INTERMAGNET DVD/CD-ROMDIRECTORY STRUCTURE

The files on the INTERMAGNET DVD/CD-ROM areset up in a particular directory structure. The rootdirectory contains a "README.TXT" file, which is anASCII file describing the DVD/CD-ROM and where toobtain information about it, the software, anddocumentation; CDs also hold a "README.EXE" file,which is an executable version of the README.TXTfile that allows the user to scroll back and forth throughthe information.

On the 1991 CD-ROM there are also twosub-directories. One is labelled "XTRAS", and the other"MAG1991". The XTRAS directory contains one filelabeled "STRUCTUR.DAT", and another"PRNSTRUC.EXE". The STRUCTUR.DAT fileprovides a schematic of the data structure for the recordson the DVD/CD-ROM and the PRNSTRUC.EXE fileenables the user to obtain a printout of that recordstructure.

The MAG1991 directory contains a sub-directory foreach observatory identified by its 3-letter ID code. Inaddition, there are sub-directories labeled "1991MAPS","CTRY_INF", and "OBSY_INF". The 1991MAPSdirectory contains the *.PCX files that are the mapimages of each country for use in the access software.These are labeled by a 3-letter country ID with the PCXextension, and one labeled "ALL.PCX" for the "AllCountries" option. The CTRY_INF directory containsa "CTRYLIST.IDX" file that is used internally, *.PCXfiles for each country (and one for ALL) that are theimages used to show the flag and organizational Logofor the different countries, and the README files thatpertain to each country's geomagnetism program(including a README for the ALL option). TheO B S Y _ I N F s u b d i r e c t o r y c o n t a i n s a"91OBSYDAT.DBF" file that is used internally in thesoftware.

The individual sub-directories (e.g. BFE for Brorfelde,TUC for Tucson, etc.) contain the 12 months of datalabeled with the 3-letter ID, 2-character year, 3-lettermonth abbreviation, and a "BIN" extension indicatingthey are binary files. For example, "BFE91AUG.BIN"is a file of 31 sequential day-records for Brorfelde, for

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1991, for August. In addition, there are the"README.XXX" files for the individual observatory,where the XXX indicates the 3-letter observatory ID.

This sub-directory may also contain a file labeled asXXXYRK.DKA, where the XXX is the 3-letterobservatory ID, the YR is the 2-character year value andthe K indicates a K-Index file. Originally the DKAextension was used to indicate that the data weregenerated from a digital algorithm in an ASCII format,however subsequently these files have been used to holdboth digitally derived and hand-scaled K indices. Sincethe 2005 CD-ROM the DKA files have been created byINTERMAGNET using data from the binary IAF file(before 2005 these files were provided by theobservatories). These ASCII K-Index files are used, eventhough the data are in the binary records, because theyare much faster to access than paging through the binaryrecords on the DVD/CD-ROM.

4.6 INTERMAGNET CD-ROMSOFTWARE

The INTERMAGNET CD-ROM software is a menu-driven program that allows the user to display data inboth graphics and text modes. It also allows the user toSave the graphics in the form of *.PCX files that canthen be imported into other programs that accept thePCX format; and also Save the text in the form of ASCIIfiles to the hard drive or floppy disk. Output may also besent to an Epson-compatible dot-matrix, or Hewlett-Packard Laserjet-compatible printer for both plots andtext.

Starting the software brings up a "Welcome" screen,and an ENTER command brings the user into the HOMEscreen, with menu options for YEAR, COUNTRY,OBSERVATORY, DATE-RANGE, AND MODE-OUTPUT. The "8" and "9" keys allow the user to scrollthrough the choices, which are highlighted as the usermoves through them. Pressing the "ENTER" key selectsthe highlighted option, and activates pop-up menus withfurther options. All options may be selected using the 8,9, and ENTER keys. Selections may also be made withthe use of "Hot Keys", which are the first letter of eachoption, and indicated in the software by use of a differentcolor in the menu choices. Pressing the particular HotKey activates that menu choice immediately. Hot Keysare indicated in this manual by the use of bold type, forexample, S(ave) means that if the "S" key is pressed forthe Save option, it is executed immediately. Once allselections have been made, the EXECUTE optionretrieves and displays the chosen options. Pressing the"ALT" and "E" keys simultaneously will exit the userback to DOS at any time, and from anywhere within theprogram.

There are 6 MODE-OUTPUT options: a) minute

value plots, b) minute values as text, c) mean hourlyvalue plots, d) mean hourly values as text, e) K-Indexvalues as text, and f) a conversion option that convertsdata from the 32-bit binary format into the World DataCenter (WDC) ASCII format. The WDC format optionwas included to allow users with existing softwaredesigned for this format to output the desired data andimport it into their existing programs.

Help screens are available throughout the program withthe use of the "F1" key. When the user is in a particularhighlighted menu item, the F1 key provides a help screenabout that item. In addition, information screens areavailable about a particular country using the "F4" key,and about the particular observatory using the "F3" key.These option keys appear on a menu bar on the screenwhen the COUNTRY and/or OBSERVATORY optionis highlighted. The user can scroll through theseREADME screens using the "8" and "9" keys, once theF3 or F4 key has been pressed.

Within the program, menu bars located at the top andbottom of the screen, offer a variety of options. A mapscreen of each country is available, showing theobservatories contributing to the CD-ROM from thatcountry, by using the V(iew map) key once the particularcountry has been chosen. Also, an A(bout) screen isavailable for each country showing the organization'saddress and the names of persons to contact regardingtheir geomagnetism program. Users can changeobservatories (within a given country) and date rangeswhile in the output mode without having to return to theHOME screen. Individual components in the plotoutputs may be selected and displayed at an enlargedscale using the C(omponent) option (Hot Key "C") fromthe menu bar. While in the Component mode, theT(oggle) key toggles on and off a histogram of hourlymeans and K-Index values (when available) for theminute plots, and the Ak values for the mean hourlyvalues plots. P(rint) and S(ave) options are alsoavailable for both graphics and text modes. Startingwith the 1992 CD-ROM, a Base(l)ine option was madeavailable that provides absolutes and baseline calibrationdata for each station. These data can be viewed either inthe form of a plot for each component, or in text modeshowing the observed and adopted values for the year.The plots also show a delta-F plot of the differencesbetween the observed and computed total field (F) forsome stations; and the text mode contains a commentssection pertaining to baseline jumps and otherobservatory adjustments.

Other options that are available from the menu barsinclude a B(eginning day) choice that resets the outputto the beginning of the selected date-range, a F2(Flow)chart of the software program that indicates where theuser is within the program and what outputs areavailable, and a R(escale) option that allows the user to

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set the scale of the plots. This feature disables the auto-scaling of the plots, and enables a user to plot data at afixed scale for comparison of different days and/orobservatories on the same full-range scale. However, ifthe data cannot fit within the plot range, the Rescaleoption will override the user-selected scale and auto-scale to fit the data. While in the HOME screen, theP(references) option allows the user to customize certainparameters including the text and background colors, thetype of printer being used, and the CD-ROM and outputdrive letter designations, it is also possible to add CRLF(carriage return / linefeed characters) to the records inany data converted to WDC-files..

Copies of DVD/CD-ROM, software anddocumentation may be obtained from:

INTERMAGNET DVD/CD-ROM distribution officeObservatoire Magnétique NationalCarrefour des 8 routesF-45340 Chambon la ForêtFRANCETel: 33 (0) 2-38-33-95-00Fax: 33 (0) 2-38-33-95-04Internet: imso@ipgp.fr

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CHAPTER 5 SATELLITES

5.1 GEOSTATIONARY SATELLITES

Orbiting the earth, 36,000 km above the equator withapproximately 72E of longitude between them are fivegeostationary satellites, METEOSAT, GOES-East,GOES-West, GMS and INSAT. The operational statusof the INSAT satellite, operated by the IndianMeteorological Agency is not clear at the present time,and it is not used for any INTERMAGNET tranmissions.The primary function of the other four satellites is toprovide regular updates, to meteorological agencies, ofcloud and infra-red image data which they use toproduce forecasts of weather conditions worldwide.Along with these imaging facilities the satellites can, atregular time intervals, relay data collected from remoteground based transmitters to users equipped withsuitable receiving and decoding equipment.

This method of data transmission is being used bymany magnetic observatories participating inINTERMAGNET to relay data from observatories inboth the northern and southern hemispheres to theINTERMAGNET GINs. Until recently, data fromobservatories in the southern hemisphere or remoteisland groups took months, or in some cases years, toreach users; but now, using satellite communications,data from an Antarctic island are available to researchersfrom an INTERMAGNET GIN within 72 hours ofrecording.

5.2 METEOSAT

Transmitting through METEOSAT, each DataCollection Platform (DCP) is allocated a one-minutetransmission slot every hour. During this time the DCPencodes and transmits, to the satellite, any data input toit during the previous 60 minutes. From the satellite, thedata are relayed to the EUMETSAT operations center atDarmstadt, Germany, where they are checked andtemporarily stored. The GIN automatically collects thedata from EUMETSAT web site. For more informationplease contact the Paris GIN manager.

5.3 GOES

Observatories transmitting through the GOESEast/West satellites output their data every 12 minutes tothe satellite and in this case there is no secondaryretransmission stage, as is done with METEOSAT. Inthe GOES system the data are transmitted directly to areceiving GIN where they are made available to users.This form of communication is simpler, but the GOESlink does require a much larger receiving antenna as

signals transmitted directly from a geostationary satelliteare at a very much lower power than those relayed usingthe METEOSAT retransmission facility. To overcomethe necessity for a large 3-5m receiving dish antenna,users in or near the United States may also access GOESEast and West transmissions using a DOMSAT(DOMestic SATellite) receiving station. This is aretransmission facility similar to that used withMETEOSAT, providing users with a much strongersignal and hence a considerable reduction in the size ofthe receiving antenna required (1.2 - 1.8m in diameter).

5.4 TRANSMISSION ACCESS

The use of satellites and the timed-transmission slots onany of the geostationary satellites is very closelycontrolled. Before an observatory can transmit datausing a satellite, an application must be made to therelevant controlling body. All transmission equipmentused must have been checked and certified to be of anacceptable standard before a licence and a transmissionslot can be granted. Also, although it may be possible togain free access to geostationary satellites, depending onthe institute and the use to which the data are being put,the satellite operators may charge users for access.

Two different types of transmission authority may benecessary before an observatory can transmit its datathrough a satellite to a GIN:

1) Authority to transmit to an Earth orbitingapparatus. This is a licence issued by thegovernment of a particular country which gives aninstitute permission to operate radio transmissionequipment. This type of licence may not benecessary, but prospective participants shouldcheck with their respective governmentdepartments to ensure that they are notcontravening any transmission laws in force intheir country.

2) Application must be made to the operators of thesatellite which can be accessed from theobservatory. Appendix B-2 shows the footprintsof geostationary satellites and from this users candecide which satellite should provide the besttransmission path. Since satellite positions aresometimes changed, those intending to operate anIMO near the edge of a footprint should contactthe satellite operators for more detailedinformation concerning the satellite accessibility.Most satellite operators have a standardapplication form. A prospective user should write

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to the operator giving details of the proposeduse to which the transmitted data is to be put, abrief description of the project and a request fora transmission slot application form.

If an application form has to be completed, it mayinclude many questions about the operator, site location,and technical questions about the type of DCP,transmission power and whether or not the proposedDCP has been certified for use on this satellite by thesatellite operators. To answer these questions, it isusually necessary to contact the DCP supplier.

The completed form is then sent to the respectivesatellite operator, who, after due deliberation willhopefully issue the applicant with a satelliteidentification number, a transmission frequency/channeland a specific time slot on the allocated channel.

Alternatively, if the user or the organization to whichthe user belongs is a member of the WorldMeteorological Organization (WMO), access to aspecific satellite and a transmission slot may be grantedsimply by quoting an identification number which hasbeen issued by the respective satellite operators to themember state or country.

The length of time slots used varies depending on thesatellite which is being accessed. A METEOSAT timeslot is 1 minute every hour. On GMS it is 90 secondsevery 12 minutes and on GOES, 20 seconds every 12minutes. During these times users transmit their data. Itis essential that the DCP clocks maintain accurate timing,as any transmission outside the allocated time slot willresult not only in corruption of the data beingtransmitted, but also of data transmitted by users onadjacent time slots.

5.5 SATELLITE OPERATORS

1) METEOSAT

EUMETSATAM Kavalleriesand 31D-64295DarmstadtGermany

Telephone: 49 61 51 80 77FAX: 49 61 51 80 75 55INTERNET: ops@eumetsat.deWEB: www.eumetsat.de

Those whose potential IMOs would be serviced byMETEOSAT are advised to first contact the PARIS GINoperator for timely information on access toMETEOSAT.

2) GOES East and West

Mr. Jim AbeytaNOAA R/E/SE325 BroadwayBoulder, CO 80303USATelephone: 1-303-497-5827Internet: James.Abeyta@noaa.gov

Those whose potential IMOs would be serviced byGOES are advised to first contact the GOLDEN GINoperators for timely information on access to GOES.

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5.6 SATELLITE SERVICES

Other methods of obtaining permission to transmit viaMETEOSAT and GOES East and West are:

1) Through MAEDS (Multisatellite ApplicationsExtended Dissemination Service), which is acommercial organization based in France. Thiscompany undertakes to arrange a satellitetransmission slot on METEOSAT and GOES.

CLS Service MEADS18, Av. Edouard BelinToulouse Cedex 31055FRANCE

2) Through North American Collection and LocationService (NACL), which is a company providingsimilar services to those provided by MAEDS.

Mr. Peter GriffithNorth American Collection & Location bySatellite9200 Basil Court, Suite 306Landover, MD 20785USATelephone: 1-301-341-1814Fax: 1-301-341-2130

These companies have been given the right byEUMETSAT to market environmental data gatheringservices.

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CHAPTER 6 DATA QUALITY CONTROL

6.1 INTRODUCTION

Quality control methods should be employed in theproduction of reported, adjusted and definitive data.Total field intensity values that are recorded using aproton precession magnetometer are an excellent tool formonitoring the measurement process that producescomponent values. The total field values may also beused to estimate the maximum likely range of error forcomponent values. Baseline values are used to adjustcomponent values for long- period, non-random error.A baseline adoption process may be used that providesconfidence limits for component 1-minute values. Atabular listing of annual baseline values and a descriptionof baseline adjustments accompany data contained onINTERMAGNET DVDs/CD-ROMs. A graphic displayof baselines and differences in computed and recordedtotal field values are available to users for stations on theINTERMAGNET DVDs/CD-ROMs.

6.2 THE OBSERVATORY MEASUREMENTPROCESS

Magnetic observatories use a variety of magne-tometers, electronics, and computer processes to obtaincomponent values of the Earth's magnetic field at 1-minute intervals. The component values recorded de-pend on the type of variometers used and the orientationof the variometer sensors. A vector diagram of compo-nent relationships is shown in figure 1. The reliability ofcomponent values may be influenced by many factors:

- orientation of variometer sensors- stability of variometer piers- filter techniques used in digitizing values- temperature coefficients of variometer sensors and

electronics- background noise of sensors and electronics- orthogonality of variometer sensors- application of absolute controls

The instruments, electronics, computer processes, andobservatory procedures are selected to minimize thenegative effects of the above factors. Quality controlprocedures should be used to monitor these influences.

Component baseline values are computed fromabsolute measurements and digitally recorded componentvalues. Absolute values of the Earth's magnetic field aremeasured by an observer and the accuracy of theabsolute values depend on several factors:

- observer skill and absence of bias

- calibration of magnetometers- accuracy of pier corrections- random error inherent in the measurement process- pier stability- magnetometer's susceptibility to environmental

influences- activity of the magnetic field during the measurement

process- field gradient

The non-random error in the absolute measurementsshould be minimized by using standard observatoryprocedures (see references in section 2.6).

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6.3 COMPUTATION OF BASELINEVALUES

The component baseline values are reported in theformat described in Appendix E-4. The general form ofthe equation for computing the baseline value for anarbitrary component `W', is shown below:

WB(k) = WO(i:j) - [WS(k) * WM(i:j)]

where:

(i:j) - is the time interval (generally severalminutes) for the measurement

(k) - is the k-th time, the average time of theinterval (i:j).

WB - is the computed baseline value

WO - is the observed absolute field value for timeinterval (i:j).

WS - is the scale value of component W of thevariometer sensor. This value is used toconvert electrical units to magnetic units. Theconversion factor may be automaticallyapplied by computer or electronics to 1-minute values. If the conversion factor is notstable, scale value measurements should bemade and recorded for baseline application.

WM - is the mean of the 1-minute component valuesrecorded during the time interval (i:j).

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6.4 BASELINE ADOPTION

A number of methods are used in observatory dataprocessing procedures to adopt baselines from observedbaseline values. An adopted baseline may be fitted tothe baseline values by hand or by a computer algorithm.The baseline values obtained from the adopted baselinefor each day are written to a file in the INTERMAGNETbaseline format IBFV2.00, (Appendix E-4). The formatincludes a section for comments pertaining to dates andtimes of baseline adjustments or changes ininstrumentation. These files must be transmittedannually to INTERMAGNET along with 1-minute datafor DVD production.

If the baseline is adopted by computer, statistics maybe generated to verify that confidence limits for theadopted baseline meet the INTERMAGNETspecifications. The confidence limits are computed fromthe variance of baseline values about the adoptedbaseline for specific segments of time. Componentconfidence limits for the annual adopted baseline may beestimated by pooling the variance of the segments. Thismay provide the user with a quantitative measure of thepossible error in component values.

Figure 2 shows observed values (circles) and adoptedbaseline values (dots) for magnetic field components X,Y, and Z for Belsk observatory during 2003. The timeseries of F-P total field differences, defined in section6.5, corresponds to the time series of adopted baselinevalues.

6.5 THE COMPUTATION OF TOTAL FIELDDIFFERENCES

One-minute total field values should be recorded inparallel with 1-minute component values taken at thesame time. The total field difference (F-P) is the totalfield computed from component values (baseline-adjusted) minus the total field value recorded by a totalfield magnetometer. The equations used for computingF-P values depend on the variometer orientation. Theequation for computing F-P for a variometer oriented tomeasure components XYZ is:

(F-P)i = [(BXi+Xi)2+(BYi+Yi)2+(BZi+Zi)2]1/2-Fi+PDF

and for HDZ orientation,

(F-P)i = [(BHi+HNi)2+HE2+(BZi+Zi)2]1/2-Fi+PDF

where:

i - is the time of the difference computation. Thetime unit may be 1-minute, mean hourly, ordaily differences.

B - denotes the baseline value for components H,X, Y, or Z.

F - is the total field value recorded using a totalfield magnetometer

PDF - is the total field pier difference, the differencebetween the total field value at the sensor, andtotal field value at the absolute pier.

HN - is the vector field of the horizontal intensityrecorded by the H sensor, as shown in figure 3.

HE - is the vector field of the horizontal intensityrecorded by the D sensor. The change indeclination (δD) is relative to the declinationof the H sensor at orientation (Do)

Do = Di -ATAN[HEi/(BHi+HNi)].Di = absolute observed declination

The F-P values may be computed from reported, adjust-ed or definitive data. Time series graphs of the F-P

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values may be produced easily and quickly at GINs.Programs may be used to produce the F-P graphs in real-time to enable GIN operators to continuously monitor theperformance of those observatories transmitting to theGIN by satellite communication. The F-P values may beused for correlation studies to isolate environmentalinfluences. The value of this technique decreases whenone component dominates the others.

The errors in component values (∆X, ∆Y, ∆Z) giverise to an error in F:

∆F = X ∆X + Y ∆Y + Z ∆Z . F F F

If we assume no change in Y (∆Y) and Z (∆Z), then theminimum detectable error that might be attributed to theX component would be: ∆X = F ∆F/X . The minimumdetectable error may be

estimated for each component. For the HDZ sensororientation similar results arise for H and Z:

∆F = H ∆H + Z ∆Z . F F

No inference can be made concerning D.

6.6 SUMMARY

Tools that might be used for quality control of reported,adjusted and definitive data have briefly been described.INTERMAGNET is establishing standards ofcomparison such as the graphs of baselines and F-Pvalues. Participating observatories may evaluate theperformance of their operations relative to the results ofother observatories. Participants communicate withother members on instrumentation procedures toimprove the quality of INTERMAGNET observatorydata.

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CHAPTER 7 WORLD WIDE WEB

7.1 INTRODUCTION

The INTERMAGNET web site provides backgroundinformation about INTERMAGNET, it's structure andit's participating organizations, countries and IMOs(INTERMAGNET Magnetic Observatories). It offersaccess to its various products including magnetogramsand data files of Reported and Adjusted Minute Meanvalues from all the IMOs, the Annual DVD/CD-ROM ofDefinitive Data, and the Technical Reference Manual.The INTERMAGNET application form can also beobtained from the web site.

7.2 WEB SITE ADDRESS

INTERMAGNET web site address is:www.intermagnet.org

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APPENDIX A-1

INTERMAGNET TERMINOLOGY

REPORTED Data:Data as output by an observatory, transmitting through

a satellite or using E-Mail. REPORTED data have nothad any baseline corrections applied, may contain spikesand may have missing values. When ADJUSTED dataare available, REPORTED data are removed from onlineaccess.

ADJUSTED Data:Each observatory or its parent institute is allowed to

modify REPORTED data files to produce ADJUSTEDdata, with a goal of 7 days after transmission. Theseadjustments may be to modify baselines, remove spikes,fill gaps etc. on any day file. When data are missingfrom an ADJUSTED data file, these data may be inputto a GIN in a later message. This new message file canbe transmitted to a GIN with the 'A' flag set in byte 25 ofeach hourly block header (Appendix E-3). ADJUSTEDdata are maintained online until the annual DVD isavailable. They are then archived by the GIN and onlyavailable thereafter by special arrangement.

DEFINITIVE Data:This describes observatory data which have been

corrected for baseline variations and which have hadspikes removed and gaps filled where possible.DEFINITIVE data have each block header byte 25 set to'D' (Appendix E-3), and the quality of the data is suchthat in this form they would be used for inclusion intoObservatory Year Books, input to World Data Centersand included in INTERMAGNET DVDs.

Reference Measurement (RM):Values provided automatically by an IMO using 2

independent instruments for inter-comparison.Reference Measurements are provided by the instituteo