gds1051 - northeast, northwest and south timmins areas

Report of the Timmins Northeast, Northwest and South airborne gravity surveys Geophysical Data Set 1051

NORTHEAST, NORTHWEST AND SOUTH TIMMINS AREAS

Ontario Airborne Geophysical surveys Gravity Data

Geophysical Data Set 1051 Ontario Geological Survey Ministry of Northern Development and Mines Willet Green Miller Centre 933 Ramsey Lake Road Sudbury, Ontario, P3E 6B5 Canada

Report of the Timmins Northeast, Northwest and South airborne gravity surveys 1 Geophysical Data Set 1051

TABLE OF CONTENTS CREDITS .....................................................................................................................................................................1

DISCLAIMER .............................................................................................................................................................1

CITATION...................................................................................................................................................................1

1) INTRODUCTION..............................................................................................................................................1

2) SURVEY LOCATION AND SPECIFICATIONS ..........................................................................................2

3) AIRCRAFT, EQUIPMENT AND PERSONNEL ...........................................................................................4

4) DATA ACQUISITION ......................................................................................................................................7

5) DATA COMPILATION AND PROCESSING ...............................................................................................8

6) FINAL PRODUCTS ........................................................................................................................................13

7) QUALITY ASSURANCE AND QUALITY CONTROL .............................................................................14

REFERENCES ..........................................................................................................................................................16

APPENDIX A TESTING AND CALIBRATION.........................................................................................17

APPENDIX B PROFILE ARCHIVE DEFINITION ...................................................................................21

APPENDIX C GRID ARCHIVE DEFINITION..........................................................................................25

APPENDIX D GEOTIFF AND VECTOR ARCHIVE DEFINITION ....................................................26


CREDITS This survey is part of the Discover Abitibi Initiative, a regional cluster economic development project based on geoscientific investigations of the western Abitibi greenstone belt. FedNor, Northern Ontario Heritage Fund Corporation and private sector investors have provided funding for the initiative. Project management was performed by the Timmins Economic Development Corporation. List of accountabilities and responsibilities: • Timmins Economic Development Corporation (TEDC) – overall project management • Robert Calhoun, Project Manager, Discover Abitibi Initiative – contract management, project

management • Laurie Reed, L.E. Reed Geophysical Consultant Inc., quality assurance and quality control • Thomas Watkins, Ministry of Northern Development and Mines (MNDM) – preparation of

base maps and map surrounds • Sander Geophysics Limited, Ottawa, Ontario - data acquisition and data compilation

DISCLAIMER To enable the rapid dissemination of information, this digital data has not received a technical edit. Every possible effort has been made to ensure the accuracy of the information provided; however, the Ontario Ministry of Northern Development and Mines does not assume any liability or responsibility for errors that may occur. Users may wish to verify critical information.

CITATION Information from this publication may be quoted if credit is given. It is recommended that reference be made in the following form: Ontario Geological Survey 2004. Ontairo airborne geophysical surveys, gravity data, Northeast, Northwest and South Timmins Areas; Ontario Geological Survey, Geophysical Data Set 1051.

1) INTRODUCTION Recognising the value of geoscience data in reducing private sector exploration risk and investment attraction, the Timmins Economic Development Corporation (TEDC), along with the FedNor, Northern Ontario Heritage fund and private sector investors funded the Northeast, Northwest, and South Timmins AIRGrav airborne gravity survey, consisting of: • airborne geophysics (high-resolution airborne gravity survey) • delivery of digital data products.


The TEDC was charged with the responsibility to manage the project. The TEDC acted on the advice of Discover Abitibi initiative sub-committees concerning the mineral industry needs and priorities. Various criteria were assessed, including: • commodities and deposit types sought • prospectivity of the geology • state of the local mining industry and infrastructure • existing, available data • mineral property status.

In late 2003 and early 2004, the TEDC managed a program of an airborne gravity survey in areas Northeast, Northwest, and south of Timmins as part of the Discover Abitibi Initiative Program. The project involved one survey contractor and 14,296 line-km of data acquisition, including 2,281 line-kilometres of un-contracted data donated by the contractor, Sander Geophysics Limited, to provide better coverage between blocks. The products of an earlier 1,836 line-kilometre airborne gravity test survey in the same area are included with the present report and database (Elieff, 2003). The airborne survey contract was awarded through a Request for Proposal and Contractor Selection process. The system and contractor selected for the survey were judged on many criteria, including the following:

• applicability of the proposed system to the local geology and potential deposit types • aircraft capabilities and safety plan • experience with similar surveys • QA/QC plan • capacity to acquire the data and prepare final products in the allotted time • price-performance.

2) SURVEY LOCATION AND SPECIFICATIONS Two main survey areas were flown (Figure 1). The North block is the larger and lies in part northwest, north and east of Timmins, Ontario stretching from just west of the 82º parallel east to the Quebec border. The towns of Timmins, Cochrane, Iroquois Falls and Kirkland Lake all fall outside but close to the North block boundary. The South block is located due south of Timmins. The North block encloses 5 sub-blocks that define the areas to be surveyed as requested by the TEDC. These are denoted Timmins West – North, Timmins West – Central, Timmins West – South, Timmins North and Timmins East. The Test Survey block is from the earlier gravity test survey. Except for the extreme southern 2.5 km, the area was covered again as part of this survey. Sander Geophyics’ AIRGrav system (Airborne Intertially Referenced Gravimeter), mounted on a fixed wing platform, was selected by the TEDC to conduct the survey.


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Figure 1: Timmins-Kirkland Lake Region Airborne Gravity Survey areas. Survey blocks as flown are shaded yellow. The contracted survey boundaries are drawn in black. The dashed polygon denotes the previous test survey area.


The airborne survey specifications are as follows: a) line spacing and direction

Line Direction Line Spacing Traverse Lines E-W 500 m & 1000 m Control Lines N-S 10000 m & 20000 m

All flight lines were extended beyond the survey boundary to ensure the aircraft was on-line well before entering the survey area, giving the gravimetric system time to settle following turns. The Timmins East block (eastern sector of North block) was flown with a 500m traverse and 10000m control line spacing while all remaining areas were flown with a 1000m traverse and 20000m control line spacing. b) terrain clearance The survey was flown using a pre-planned drape surface designed to guide the aircraft over the topography in a consistent manner as close to minimum clearance as possible. The drape surface was prepared using digital elevation model (DEM) data obtained from Natural Resources Canada CDED (Canadian Digital Elevation Data) grids. The data was merged into a single topography grid and trimmed to the survey boundary plus an extension beyond the boundary to allow the aircraft to achieve the drape before coming on line. The grid was smoothed based on the climbing and descending capabilities of the survey aircraft, 150'/nm, to create a smooth drape surface. The minimum terrain clearance of 200 m was added to the drape surface. The result was that 95% of the survey area was flown at < 253 m AGL. c) aircraft speed

• nominal aircraft speed is 50 m/sec d) data recording

• Terrain clearance provided by the radar altimeter at intervals of 0.25 second and by the laser altimeter at intervals of 0.01 second;

• Airborne GPS positional data recorded with a 0.1 second sampling rate; • Ground-based GPS positional data recorded with a 0.1 second sampling rate; • Gravimeter data recorded with a 128 Hz sampling rate.

3) AIRCRAFT, EQUIPMENT AND PERSONNEL Aircraft and Geophysical On-Board Equipment Survey Aircraft: Cessna Grand Caravan 208B. The Cessna 208B Grand


Caravan is an all metal, high wing single-engined aircraft powered by a Pratt & Whitney Canada PT6A-114A engine driving a constant speed, full feathering, reversible propeller. The aircraft has fixed gear, extendable flaps, manually adjustable trim tabs, full de-icing equipment, and sufficient avionics for instrument flying. The aircraft can be equipped with a rigid aluminum and composite material 3 m tail stinger designed to accommodate a magnetometer sensor. The aircraft used for this survey have Canadian registrations C-GSGW & C-GSGU and conform to Canadian aeronautical regulations in survey configuration

Operator: SANDER GEOPHYSICS LIMITED

260 Hunt Club Road Ottawa, ON K1V 1C1 Ph: 613 521-9626 Email: [email protected] Web: www.sgl.com

Registrations: C-GSGU and C-GSGW Survey Speed: 100 knots / 110 mph / 50m/sec. Gravimeter: SGL AIRGrav. The AIRGrav airborne gravimeter uses a

Schuler tuned inertial platform. This platform supports three orthogonal accelerometers, which remain fixed in inertial space, independent of the manoeuvres of the aircraft, allowing precise correction of the effects of the movement of the aircraft. Accelerometer data are recorded at 128 Hz. SGL’s airborne gravimeter is relatively tolerant of turbulent conditions. It delivers good results when flown under normal weather and turbulence conditions, similar to the conditions required for high-resolution magnetometer surveys. The instrument delivers gravity data consistently with a noise level better than 0.5 mGal with a half sine wave ground resolution of 1.8 to 2 km.

Digital Acquisition: SGL NavDAS. NavDAS is the latest version of airborne

navigation and data acquisition computers developed by SGL. This system displays all incoming data on an LCD flat panel screen for in-flight data verification. The time base (UTC) accuracy of the NavDAS system is automatically provided by the GPS receiver. The NavDAS incorporates a magnetometer coupler, an altimeter converter, and a GPS receiver.


Navigation and flight path: Navigation and flight path recovery were provided by the SGL NavDAS system. The system utilizes a NovAtel Millennium 12-channel GPS receiver mounted in a computer-based navigation computer with a sampling rate of 0.1 s. In addition to providing essential positional data, the navigation computer processes raw GPS or real-time differentially corrected GPS (RDGPS) data, and compares the data to the coordinates of a theoretical flight plan, to guide the pilot along the desired survey line in three dimensions.

Barometric Altimeter: Sensotec barometric altimeter sensor. The pressure sensor

has an accuracy of ± 4 metres, a resolution of 2 metres, and a range up to 30,000 feet.

Radar Altimeter: TRT ERT 530A digital radar altimeter. The TRT radar

altimeter has a resolution of 0.5 metres, an accuracy of 1%, and a range of 1 to 8,000 feet.

King KRA-10A Radar Altimeter. The King radar altimeter has a resolution of 0.5 m, an accuracy of 1 percent, a range of 1 to 2,500 ft, and a 4 Hz data rate. This system is employed as a backup system and not actively employed for survey guidance or data acquisition.

Laser Altimeter: Optech ADM4 laser rangefinder. The Optech laser altimeter is an eye safe laser, has a range of 300m, a resolution of 0.1m with an accuracy of 5 cm. The sample rate is 100 Hz.

Base Station Equipment

Digital Acquisition: SGL GND-ACQ. The Ground Data Acquisition computer is a portable PC-Pentium with an internal GPS card. The time base (UTC) of both the ground and airborne systems is automatically provided by the GPS receiver, ensuring proper merging of both data sets. The ground data acquisition computer displays all incoming data on a LCD flat panel screen for visual inspection. The GPS data, sampled every 0.1 s, were recorded on the internal hard drive of the computer using the same format as the airborne data. The entire ground data acquisition system is fully automatic and was set for unattended recording. The ground station was also equipped with a magnetometer for monitoring magnetic storms since high ionospheric activity levels may affect GPS data accuracy.


GPS Receiver: NovAtel Millennium. The NovAtel Millennium 12-channel

receiver forms an integral part of the SGL GND-ACQ system. It provides averaged position and raw range information of all satellites in view, sampled every 0.1 s. The comparative navigation data supplied during all production flights allows for post-processed differential GPS (DGPS) corrections for the entire project.

Field Office Equipment

Computers: Processing was performed on standard desktop computers equipped with Pentium CPUs and Windows operating system. SGL’s proprietary geophysical software was used for data processing. A wide carriage continuous feed Epson 1520 colour inkjet printer was used for plotting data traces and preliminary maps.

Field Personnel The following personnel were on-site during the acquisition program.

Field Operations Manager /Geophysicist Feargal Murphy, Carlos Cifuentes

Geophysicist Max Schroeder, Jonas Holliss

Technician Phil Unhola

Engineer Mark Ovenden

Aircraft Engineer Craig Dennis

Pilot Norman Boudreault, Saeed Soldhost

Co-pilot Tristan Andrew, Essam Hassan

The above personnel were responsible for the operation and data handling from the aircraft. The project manager at the head office in Ottawa was Reed Archer. All personnel were employees of SGL.

4) DATA ACQUISITION Flight operations were conducted from the Timmins airport. The field office was established at the Cedar Meadows Resort in Timmins. Two GPS ground stations were installed on the Cedar Meadows Resort property. A remote GPS ground station was installed near the village of Ramore in the eastern part of the North block. The positions of the ground station GPS antennae were


differentially corrected using data from a GPS reference station in Algonquin Park that is part of the International GPS Service (IGS) network. This Algonquin station itself was also used as a GPS base station for the flights. The positions of the GPS antennae after differential correction were (WGS-84 datum): GPS1: 48:29:30.6930N 81:21:43.9498W 236.34m GPS2: 48:29:31.8837N 81:21:42.5930W 236.44m GPS3: 48:27:58.8146N 80:19:26.5983W 250.15m Algonquin IGS: 45:57:20.8809N 78:04:16.9241W 201.11 m A total of twenty seven production flights were performed over the period from Dec 6th, 2003 to Jan 28th, 2004. Radar and laser altimeter calibrations for each aircraft were performed prior to mobilization to Timmins. Gravimeter calibrations were performed on the ground during the course of the survey. Details of these tests and their results are given in Appendix A. Preliminary processing for on-site quality control was performed in the field as each flight was completed. This included routine tracing of analog records, verifying the data on the computer screen, and plotting of the DGPS flight path data. Final data processing and map production were performed at SGL head office in Ottawa.

5) DATA COMPILATION AND PROCESSING Gravity Data Gravity data are recorded at 128 Hz. Accelerations are filtered and decimated to match GPS measurements using specially designed filters to avoid biasing the data. Gravity is calculated by subtracting the GPS derived aircraft accelerations from the inertial accelerations. In survey flying, accelerations in an aircraft can reach 0.1 G, equivalent to 100,000 mGal. Data processing must extract gravity data from this very noisy environment. This is achieved by modelling the movements of the aircraft in flight by extremely accurate GPS measurement. The calculated gravity is corrected for the Eötvös effect and normal gravity and the sample interval is reduced to 2 Hz. These operations are all performed by SGL’s proprietary GRAVGPS software. The following standard corrections were applied to the gravity data to calculate the Bouguer anomaly data:

a) Eötvös correction = -vx2*cosΦ/((r+h) cosΦ) - 2*0.00007292115*cosΦ*vx -

vy2/(r+h), where Φ is the latitude of the aircraft, vx

and vy are the velocities of the aircraft in the x (north) and y (east) direction, r is the Earth’s radius at the latitude Φ, and h is the altitude of the plane above the GRS-80;

b) Normal gravity = 9.7803267714*(1+0.00193185138639*sin2Φ)/ sqrt(1-0.00669437999013* sin2Φ), where Φ is the latitude of the aircraft;

c) Free air correction, gfa = -0.3086 h, where h is height of the aircraft in metres;


d) Bouguer, gsb = 2πγρh = 0.041925 ρh, where γ is the Universal Gravity constant, ρ is density of rock (2.67g/cm3 for this project), and h is height of the ground below the aircraft in metres;

e) Curvature of the earth, gec = 1.464 h - .3533 h2 + .000045 h3, where h is height of the ground in kilometres;

f) Terrain, gt. See below for a description of the terrain correction technique; g) Static correction, gsc, based on static ground recordings and repeat lines; h) Level Correction, glc , based on line intersections;

Thus Bouguer anomaly = G - gfa - gsb - gec + gt - gsc - glc , where G is the calculated gravity adjusted for Eötvös effect and normal gravity. Terrain corrections were computed using software developed for SGL through the University of Calgary Geomatics department. The algorithm employed for this project calculates terrain corrections using 2D FFT methods with a constant density of 2.67 g/cm3. Corrections were computed using terrain derived from several sources that were merged together. Within the survey area, the line data were used to calculate the topography by subtracting the altimeter data from the altitude of the aircraft above the mean-sea-level. The laser altimeter was primarily used, but in places where there were gaps in laser altimeter coverage the radar altimeter was used to fill the gaps. Gaps in laser altimeter coverage are normal for this type of instrument over water or when the height above ground exceeds roughly 300 m. Terrain data for the area immediately outside the survey block came from ten 3 arc second CDED (Canadian Digital Elevation Data) grids purchased from Natural Resources Canada. This terrain data was also used in the creation of the drape surface used for aircraft height guidance. Finally, a 30 arc second digital terrain model downloaded from the USGS at edcdaac.usgs.gov/gtopo30/gtopo30.html provided coverage up to 160km from the survey block The gravimetric data were levelled to compensate for instrument variations in two steps. A single constant shift determined from ground static recordings was applied on a flight-by-flight basis. Control line intersection statistics were then used to adjust individual lines with a constant shift. The AIRGrav system is very stable so the control line levelling adjustments are small, typically within +/-1 mGal. Grids of the free air and Bouguer anomaly were generated by filtering the line data with a 70 second full sine wave filter to remove high frequency noise and then averaging the filtered line data within the grid using a spatial filter with a mid point of 2.7 km (0% pass at 2.0 km, 100% pass at 4.0 km), full sine wave length, or 1.35 km half sine wave length. Grids were generated using a minimum curvature algorithm to create a two-dimensional grid equally incremented in X and Y directions. The algorithm produces a smooth grid by iteratively solving a set of difference equations minimizing the total second horizontal derivative, while attempting to honour the input data (Briggs, 1974).


Radar and Laser Altimeter Data The terrain clearance measured by the radar altimeter in metres, was recorded at 4 Hz. The laser altimeter recorded terrain clearance at 100 Hz. The laser altimeter was used for terrain calculations over most of the area because of its higher resolution. In cases where there was no laser altimeter data available, radar altimeter data has been substituted. Positional Data A number of programs were executed for the compilation of navigation data in order to reformat and recalculate positions in differential mode. SGL’s GPS data processing package, GPSoft, was used to calculate DGPS positions from raw 10 Hz range data obtained from the moving (airborne) and stationary (ground) receivers using a linear combination of L1 and L2 phase. The calculations were made using a converging ambiguities algorithm resulting in an accuracy of better than 0.5 m. The general data flow for GPSoft is illustrated in Figure 2. Accurate locations of the GPS antennae were determined by differentially correcting the SGL ground station position data using a permanent GPS reference station (see Section 4 – Data Acquisition). This technique provides a final receiver location with an accuracy of better than 5 cm. The entire airborne data set was processed differentially using the calculated ground station location. The GPS is processed repeatedly to obtain optimal aircraft accelerations for the calculation of gravity. In addition to using SGL’s ground stations in Timmins, supplemental GPS processing was performed using the IGS station in Algonquin. Despite the longer base line of approximately 375 km, accelerations equivalent to those derived from SGL’s ground stations were achieved for most lines. Positional data were recorded in the WGS-84 datum in latitude and longitude. For processing purposes, the WGS-84 UTM data were calculated in UTM zone 17N. Parameters for the WGS-84 datum are:

Ellipsoid: Semimajor axis: 1/flattening:

GRS-80 6378137.0 298.257222


Figure 2: Positional Data Processing

POSITIONAL DATA PROCESSING

Quality Control Check

FINAL FLIGHT PATH DATA

FLIGHT PATH PLANNING DATA

GPSOFTPerform differential correction and

reformat corrected GPS to SGL format

XYPLOTPlot raw GPS flight path

XYZCVTConvert from LAT/LONG to UTM and

perform datum conversion

SEQ2MAPCreate file of first and last points

for each planned flight line

TRIMCTLDetermine trimming for flight path

COMBINSplit data into line format

REMDATCreate file of first and last points for each

planned flight line

DATONReformat raw GPS line data to SGL format

ALTIMETER DATA(line format)

AIRBORNE GPSPOSITIONAL DATA

GPS GROUNDSTATION DATA

XYPLOTPlot DGPS flight path

HGT2MSLConvert WGS-84 Z to mean sea level Z


For delivery, the data were transformed to NAD-83 datum in UTM zone 17N. Parameters for the NAD-83 datum are:

Ellipsoid: Semimajor axis: 1/flattening: conversion from WGS-84

GRS-80 6378137.0 298.257222 dX = 0.991m, dY=-1.9072m, dZ=-0.5129m X rotation=1.2581E-7 radians, Y rotation=0.3599E-7 radians, Z rotation=0.5607E-7 radians

Data was also transformed to NAD-27 NTv2 (20 min) datum in UTM zone 17N using Geosoft. Parameters for the NAD-27 datum are:

Ellipsoid: Semimajor axis: 1/flattening: conversion from WGS-84

Clarke 1866 6378206.4 294.979 NTv2 (20 min) transform

Elevation data were recorded relative to the GRS-80 ellipsoid and transformed to mean sea level (MSL) using the Canadian NGSD91 geoid undulation model. Personnel The following personnel were involved in the compilation of data and creation of the final products: Data Processing Manger Luise Sander Gravity Processing Feargal Murphy / Stefan Elieff


6) FINAL PRODUCTS Map products at 1:100,000 The map products are divided onto three map sheets covering the Northwest Timmins Area (Groundhog River to Frederick House River), Northeast Timmins Area (Highway 101 Corridor), and South Timmins Area (Peterlong Lake to Whitefish River). The map products are: • Colour image of the terrain-corrected bouguer gravity, plotted with flight paths on a

planimetric base • Colour image of the first vertical derivative of the terrain-corrected bouguer gravity, plotted on

a planimetric base • Shaded colour image of the digital elevation on a planimetric base Profile databases • Gravity database at 2 samples/sec in both Geosoft® GDB and ASCII format Data grids Geosoft® data grids, in both GRD and GXF formats, provided in NAD83 and NAD27 datums of

the following parameters: • Digital terrain model • Free air gravity • Terrain-corrected bouguer gravity • First vertical derivative of the terrain corrected bouguer gravity. GeoTIFF images GeoTIFF images correspond to the map products listed above. DXF vector files for each map area • Flight path • Contours of the terrain-corrected bouguer gravity • Contours of the first vertical derivative of the terrain corrected bouguer gravity • Contours of the digital terrain model Project report Provided in both Microsoft WORD® and Adobe® PDF formats.


7) QUALITY ASSURANCE AND QUALITY CONTROL Quality assurance and quality control (QA/QC) were undertaken by the survey contractor (Sander Geophysics Limited), and by L.E. Reed Geophysical Consultant Inc. Stringent QA/QC is emphasized throughout the project. Survey Contractor Important checks are required during the data acquisition stage to ensure that the data quality is kept within the survey specifications. The following lists in detail the standard data quality checks that were performed during the course of the survey. Daily quality control Navigation data

• The differentially corrected GPS flight path is compared with the theoretical flight

path and drape surface to ensure proper terrain clearance and line spacing is maintained.

• Data (radar, laser, barometric and GPS) are checked for consistency. Checking

programs are run to evaluate the data for completeness, gaps, time problems, aircraft speed, data activity and range. The recorded time is examined to ensure that it is increasing continuously at the correct increment. Other data are analysed to ensure that they are within a predetermined range and activity level. Each program also has internal checks for unusual and/or out-of-spec data and error situations. Listings produced by the program display any of these situations. These listings are also examined by the Project Geophysicist and Project Manager

Gravity data

• Before and after each flight, the gravity readings are confirmed and instrument drift monitored by measuring gravity on the ground for 10 minutes or more. During this time, contact with the aircraft is avoided to minimize accelerations caused by aircraft motion. This period is also used as an initialization period when the differential GPS data processing is performed, resulting in better accuracy. An initial estimate of the local gravity reading is made at the aircraft based on real-time readings on the instrument display and recorded in a log book. Later, during data processing, the entire static period is viewed in profile and analyzed. Daily before-flight and after-flight average readings are plotted and monitored for signs of instrument drift.

• Preliminary gravity data is plotted in profile after each flight with other data channels,

such as terrain elevation, accelerations, and satellite accuracy.


• Gravity and GPS data are processed and combined through to the stage of Eötvös, free air, and simple bouguer corrections in the field in order to evaluate the quality of the acquired data. Data for each survey area is levelled, gridded and plotted as preliminary colour maps before the end of the field operations.

• In addition to the visual inspection of profiles and maps, gravity data quality for

individual lines are evaluated using noise statistics derived from comparisons with adjacent lines and control line intersections. This facilitates the identification of potential reflights as the survey progresses.

Preliminary field products Near-final products of the profile and data were made available to L.E. Reed Geophysical during visits to the survey site, for review and approval, prior to demobilization. Quality control in the office Review of field processing of Gravity data. Field processing results are reviewed at SGL’s head office. One of the most important data checking procedures is the production of data profiles before, during and after data compilation. All data streams (Bouguer gravity, magnetic total field, latitude, longitude, barometric altimeter, radar altimeter, and ground station) are profiled when received, during intermediate processing and just before production of the final data sets. In addition, profiles are produced at various intermediate stages. If any spikes exist, special attention will be paid to the data before and after spike removal to ensure that the data have not been altered. All profiles will be examined by the Project Geophysicist and any controversial data will be discussed with the Technical Inspector. L.E. Reed Geophysical Consultant Inc. L.E. Reed Geophysical Consultant Inc. conducted on-site inspections during data acquisition, focusing initially on the data acquisition procedures, base station monitoring and instrument calibration. As data was collected, it was reviewed for adherence to the survey specifications and completeness. Any problems encountered during data acquisition were discussed and resolved. L.E. Reed reviewed interim and final digital and map products throughout the data compilation phase to ensure that the products adhered to the contract specifications. MNDM prepared the base map and map surround information required for the digital and hard copy maps. L.E. Reed and MNDM ensured that the digital files adhered to the specified ASCII and binary file formats, that the file names and channel names were consistent. The map products were carefully reviewed in digital and hard copy form to ensure legibility and completeness.


REFERENCES Briggs, Ian, 1974, Machine contouring using minimum curvature, Geophysics, v.39, pp.39-48. Elieff, S., 2003, Project report for an airborne gravity evaluation survey, Timmins, Ontario: Report produced for the Timmins Economic Development Corporation on behalf of the Discover Abitibi Initiative. (http://www.discoverabitibi.com/technical-projects.htm


APPENDIX A TESTING AND CALIBRATION GRAVIMETER CALIBRATION The gravimeter’s accelerometers were calibrated before the beginning of the survey. On start up before each flight, the AIRGrav system automatically aligns and calibrates its gyros. Before and after each flight, the consistency of the measured gravity was confirmed by recording data at a fixed location on the ground. The results, presented in Table 1, are given as deviations from a local gravity value of 9.8082771 m/s2 (Canadian Gravity Standardization Network station 9201-1975 – Timmins Airport Terminal). Table 1: Pre- and Post-Flight AIRGrav Static Reading in mGal.

Flt # Pre-Flight Post-Flight 1 -0.80 -0.24

2 -1.87 -0.11

3 -1.80

4 -0.75 -0.41

5 -0.92 -1.40

6 0.28 -0.54

8 0.41 0.48

9 -2.72 -0.55

10 2.65 0.48

11 -0.04 0.76

12 -0.51 0.63

13 0.62 -0.64

14 1.31 1.85

15 0.23 1.84

16 2.55 3.32

501 -5.09 -5.99

502 -5.42 -6.31

503 -0.59 -1.67

504 -1.92 -0.48

505 0.16 -1.10

506 -5.40 -5.81

507 -5.04 -5.05

508 -0.62 -1.25

509 -1.00 -2.71

510 -2.44 -0.92

511 0.23 -0.53

512 0.54 2.72

513 0.79 -0.58


As Table 1 demonstrates, the AIRGrav system is very stable. There is no post-flight static recording for flight 3 due to a second flight immediately followed in the same day. A number of accelerometer calibrations were performed over the course of the survey. A gravity reference point is located in the terminal building at Timmins airport. This value was used for reference. RADAR AND LASER ALTIMETER CALIBRATION A test flight to calibrate the radar and laser altimeters on aircraft C-GSGU was flown on November 20, 2003. Five passes were flown over a runway at heights from 80 m to 500 m above ground. The radar and laser altimeter values were compared to the post-flight differentially corrected GPS altitude information to calibrate the altimeters. Ideal altimeters would yield a slope of 1, and an intercept of 0. For the laser altimeter test, the calculated slope was 1.007, and the intercept 0.03 m, while for the radar altimeter the slope was 0.992 and the intercept 2.56 m. A similar test was flown on October 19, 2003 to calibrate the altimeters on aircraft C-GSGW. For the laser altimeter test, the calculated slope was 1.003, and the intercept 1.68 m, while for the radar altimeter the slope was 1.014 and the intercept 0.37m.These results are well within the expected accuracy of the altimeters. Please refer to the graphs in Figures 3 to 6, which illustrate the results of the altimeter tests. Figure 3: Radar Altimeter Tests C-GSGU

Radar Altimeter Test - 20 November 2003 - Gatineau Airport

y = 0.9918x + 2.5679R2 = 1

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0 100 200 300 400 500 600

GPS (m)

Rad

ar (m

)


Figure 4: Laser Altimeter Tests C-GSGU

Figure 5: Radar Altimeter Tests C-GSGW

Radar Altimeter Test - 19 October 2003 - Kugluktuk Airport

y = 1.0145x + 0.3761

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GPS above Runway (m)

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ar (m

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Laser Altimeter Test 20 November 2003 - Gatineau Airport

y = 1.0066x + 0.0294R2 = 1

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GPS (m)

Lase

r (m

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Figure 6: Laser Altimeter Tests C-GSGW

Laser Altimeter Test - 19 October 2003 - Kugluktuk Airport

y = 1.0034x + 1.6814

020406080

100120140160

0 50 100 150

GPS above Runway (m)

Lase

r (m

)


APPENDIX B PROFILE ARCHIVE DEFINITION Data File Layout The files for the Timmins-Kirkland Lake region gravity survey 1051 are archived as a 2 CD set. Files for the previous Timmins Test survey are also included for completeness. To differentiate between these two data sets, a prefix of “te” is used for Test Survey data files, “tk” for Timmins-Kirkland lake data files, and “t_” for files which contain merged data from both surveys. The Timmins Test Survey data provided here has been modified slightly from its original form. An NAD-27 UTM X and Y channel has been added to the profile data and grid file names have been changed. This has been done for consistency with the Timmins-Kirkland Lake data set. The data itself is identical to the previously released version. The data format information in the original Test Survey report is superseded by the information provided here. File content is divided as follows: CD - 1051a

- ASCII (GXF) grids - ASCII profile database (2 Hz sampling) - DXF files of each of the three map areas:

- Flight path - Contours of terrain-corrected bouguer gravity - Contours of the first vertical derivative of the terrain-corrected bouguer gravity - Contours of the digital terrain

- GEOTIFF images (100 dpi) of each of the three map areas: - Terrain-corrected bouguer gravity - First vertical derivative of the terrain-corrected bouguer gravity - Digital terrain

- Project report (Microsoft Word® and Adobe® PDF formats) CD - 1051b

- Geosoft® Binary (GRD) grids - Profile database (2 Hz sampling) in binary GDB format - DXF files of each of the three map areas:

- Flight path - Contours of terrain-corrected bouguer gravity - Contours of the first vertical derivative of the terrain-corrected bouguer gravity - Contours of the digital terrain

- GEOTIFF images (100 dpi) of each of the three map areas: - Terrain-corrected bouguer gravity - First vertical derivative of the terrain-corrected bouguer gravity - Digital terrain

- Project report (Microsoft Word® and Adobe® PDF formats)


Coordinate Systems The profile database contains several coordinate systems: - Universal Transverse Mercator (UTM) projection, Zone 17N, NAD27 datum - Universal Transverse Mercator (UTM) projection, Zone 17N, NAD83 datum - Universal Transverse Mercator (UTM) projection, Zone 17N, WGS84 datum - Latitude/longitude coordinates, NAD27 datum - Latitude/longitude coordinates, NAD83 datum The gridded data are provided in two UTM coordinate systems, differentiated by the suffix “83” or “27” in the file names: - Universal Transverse Mercator (UTM) projection, Zone 17N, NAD27 datum - Universal Transverse Mercator (UTM) projection, Zone 17N, NAD83 datum DXF files, Geotiffs, and paper map products are in NAD83 UTM Zone 17N. Line Numbering The traverse line numbering convention for the Timmins-Kirkland Lake survey is as follows: Line number x 100 + part number i.e. Line 2205 part 1 is identified as 220501 The same convention is used for the labeling of the control lines. The Timmins Test survey uses only 1 digit to define the part number, ie. 22051. Profile Data The profile data are provided in two formats, one ASCII and one binary: ASCII - tkAirGrav.xyz - ASCII XYZ file, sampled at 2 Hz, Timmins-Kirkland Lake region - teAirGrav.xyz - ASCII XYZ file, sampled at 2 Hz, Timmins Test survey Binary - tkAirGrav.gdb – Geosoft® OASIS montaj binary database file (no compression), sampled at

2 Hz, Timmins-Kirkland Lake region - teAirGrav.gdb – Geosoft® OASIS montaj binary database file (no compression), sampled at

2 Hz, Timmins Test survey


The contents of tkAirGrav.xyz/.gdb (both file types contain the same set of data channels) are summarized as follows: Column Name Contents Format Units 1 Line Line Number I7

2 Flt Flight Number I4

3 Year Year I5

4 Day Julian Day I5

5 Time Seconds After Midnight (UTC) F9.2 Second

6 N83Lat NAD-83 Latitude F12.7 Degrees

7 N83Long NAD-83 Longitude F12.7 Degrees

8 W84X WGS-84 UTM X Zone 17N F10.2 M

9 W84Y WGS-84 UTM Y Zone 17N F11.2 M

10 W84Z WGS-84 GPS Z F7.2 M

11 N83X NAD-83 UTM X Zone 17N F10.2 M

12 N83Y NAD-83 UTM Y Zone 17N F11.2 M

13 N83Z NAD-83 GPS Z F7.2 M

14 N27CX NAD-27 NTv2 UTM X Zone 17N F10.2 M

15 N27CY NAD-27 NTv2 UTM Y Zone 17N F11.2 M

16 N27CLat NAD-27 NTv2 Latitude F12.7 Degrees

17 N27CLong NAD-27 NTv2 Longitude F12.7 Degrees

18 MSL Height above mean sea level F7.2 M

19 ALT Altimeter (Height above Mean Sea Level – Topography) F7.2 M

20 TOPO Topography F7.2 M

21 FX Gravimeter X accelerometer F12.2 mGal

22 FY Gravimeter Y accelerometer F12.2 mGal

23 FZ Gravimeter Z accelerometer F12.2 mGal

24 Eot Eotvos Correction F8.2 mGal

25 E70s Eotvos Correction, 70s Filter F8.2 mGal

26 RawGrav Raw Gravity F10.2 mGal

27 FAGUnf Free Air Gravity F10.2 mGal

28 FAG70s Unlevelled Free Air Gravity, 70s Filter F8.2 mGal

29 FAL2.7 Levelled Free Air Gravity, 2.7 km Full Wave Length F8.2 mGal

30 SBC70S Bouguer Correction, 2.67 g/cc F8.2 mGal

31 ECC70S Earth Curvature Correction F8.2 mGal

32 TC70S Terrain Correction, 2.67 g/cc F8.2 mGal

33 BG70s Unlevelled Bouguer Gravity, 70s Filter F8.2 mGal

34 LC2.7 Level Correction, 2.7km Full Wave Length Spatial Filter F8.2 mGal

35 LB Levelled Bouguer Corrected Gravity, 2.7km Full Wave F8.2 mGal


The contents of teAirGrav.xyz/.gdb (both file types contain the same set of data channels) are summarized as follows:

Column Contents Format Units

1 Line Number A6

2 Flight Number A4

3 Year A5

4 Julian Day A5

5 Seconds After Midnight (UTC) F9.2 seconds

6 NAD-83 Latitude F12.7 degrees

7 NAD-83 Longitude F12.7 degrees

8 WGS-84 UTM X Zone 17N F10.2 m

9 WGS-84 UTM Y Zone 17N F11.2 m

10 WGS-84 GPS Z F7.2 m

11 NAD-83 UTM X Zone 17N F10.2 m

12 NAD-83 UTM Y Zone 17N F11.2 m

13 NAD-83 GPS Z F7.2 m

14 NAD-27 NTv2 UTM X F10.2 m

15 NAD-27 NTv2 UTM Y F11.2 m

16 Height above mean sea level F7.2 m

17 Laser altimeter F7.2 m

18 Topography F7.2 m

19 Gravimeter X accelerometer F12.2 mGal

20 Gravimeter Y accelerometer F12.2 mGal

21 Gravimeter Z accelerometer F12.2 mGal

22 Eotvos Correction F8.2 mGal

23 Eotvos Correction, 85s Filter F8.2 mGal

24 Raw Gravity F10.2 mGal

25 Free Air Gravity F10.2 mGal

26 Unlevelled Free Air Gravity, 85s Filter F8.2 mGal

27 Levelled Free Air Gravity, 1.8km Filter F8.2 mGal

28 Bouguer Correction, 2.67 g/cc F8.2 mGal

29 Earth Curvature Correction F8.2 mGal

30 Terrain Correction, 2.67 g/cc F8.2 mGal

31 Unlevelled Bouguer Gravity, 85s Filter F8.2 mGal

32 Level Correction, 1.8km Filter F8.2 mGal

33 Levelled Bouguer Corrected Gravity, 1.8km Filter F8.2 mGal


APPENDIX C GRID ARCHIVE DEFINITION Gridded Data The gridded data are provided in two formats, one ASCII and one binary:

*.gxf - Geosoft® ASCII Grid eXchange Format (revision 3.0, no compression) *.grd - Geosoft® OASIS montaj binary grid file (no compression)

The grids are summarized as follows (## is 27 for NAD27 grids and 83 for NAD83 grids):

Grid Name Units Grid Cell Size Description

tkFAIR##.GRD mGal 200 m Free-air corrected gravity , 2.7km full wave length spatial filter

t_FAIR##.GRD mGal 200 m As above, but including lines from test survey

te_FAIR##.GRD mGal 250 m Free-air corrected gravity , 2.85km full wave length spatial filter, test survey only

tkBOUG##.GRD mGal 200 m Terrain corrected Bouguer gravity, 2.7km full wave length spatial filter, 2.67 g/cm3 density

t_BOUG##.GRD mGal 200m As above, but including lines from test survey

te_BOUG##.GRD mGal 250 m Terrain corrected Bouguer gravity, 2.85km full wave length spatial filter, 2.67 g/cm3 density, test survey only

tkBGFVD##.GRD Eötvös 200 m 1-VD of Terrain corrected Bouguer gravity, 2.7km full wave length spatial filter, 2.67 g/cm3 density

t_BGFVD##.GRD Eötvös 200m As above, but including lines from test survey

tkTER##.GRD m 200 m Derived Topography (height above sea level)

t_TER##.GRD m 200 m As above, but including lines from test survey


APPENDIX D GEOTIFF AND VECTOR ARCHIVE DEFINITION The GeoTIFF images and DXF vectors are divided onto three map sheets covering the Northwest Timmins Area (Groundhog River to Frederick House River), Northeast Timmins Area (Highway 101 Corridor), and South Timmins Area (Peterlong Lake to Whitefish River). These are denoted by the prefixes “NW”, “NE”, and “S_” respectively. GeoTIFF Images Geographically referenced colour images are provided in GeoTIFF format for use in GIS applications. xxBoug.tif Colour image of the terrain-corrected bouguer gravity, plotted with flight

paths on a planimetric base xxBgFVD.tif Colour image of the first vertical derivative of the terrain-corrected

bouguer gravity, plotted on a planimetric base xxTer.tif Shaded colour image of the digital elevation on a planimetric base Vector Archives Vector line work from the maps is provided in DXF(v12) ASCII format as follows: xxFltPath.dxf Flight path with line numbers and time markers xxBougContours.dxf Terrain-corrected bougure gravity contours xxBgFVDContours.dxf First vertical derivative of the terrain-corrected bouguer gravity,

plotted on a planimetric base xxTerContours.dxf Digital elevation contours The layers within the DXF files correspond to the various object types found therein and have intuitive names.

gds1051 - northeast, northwest and south timmins areas

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