conner - datums

7/28/2019 Conner - Datums

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PROJECTIONS, COORDINATE SYSTEMS, ANDDATUMS - EXPLAINED

Ohio Geospatial Technology Conference for Agricultureand Natural Resource Applications

March 26, 2003

David Conner

National Geodetic Survey

Geodetic Advisor to the State of [email protected] (614) 292-1619

www.ngs.noaa.gov


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The geodetic layer is the key to a GIS

Strong GIS/LIS

and engineeringsystems require

well determined

coordinatesystems and

accurate spatial

references


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The Shape of the Earth Earth is not flat

Earth is not a sphere An ellipsoid is a simplified model of

Earths shape A datum is a set of reference locations,

including elevations, describing more

precisely the surface of the Earth


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Earth Models & Datums

Ellipsoid Geoid relationship

Hh

Ellipsoid

GRS80

H = Orthometric Height (NAVD 88)

Geoid

H = h - N

TOPOGRAPHIC SURFACE

h = Ellipsoidal Height (NAD 83)

N = Geoid Height (GEOID 99)

NSea Level


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Common Ellipsoids and Datums

NAD27(North American Datum of 1927): A systemderived from land-based surveys, using the Clarke(1886) ellipsoid.

NAD83: A satellite-based system using the center ofthe earth as a reference point using measurementstaken in 1980, and adopted internationally as GRS80(geodetic reference system 1980).

WGS84 (World Geodetic System 1984): A refinement

of GRS80 used by the US military (and therefore byGPS).

For most geographic purposes, NAD83, GRS80, and

WGS84 are equivalent.


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Projection types

Projections convert spherical coordinates (latitude-longitude) to planar coordinates.

Three fundamental types of projections: Azimuthal: projection onto a planar surface

Cylindrical: projection onto a cylinder, which is then

unrolled to a plane. Conic: projection onto a cone, which can be unrolled to

a plane.

All projections create distortions of either shape,area, distance, or more than one of these.


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Three common coordinate

systems used in GIS Geographic (Lat-Long)

UTM (Universal Transverse Mercator) State Plane Coordinate System (SPCS)

SPCS Projection is either Transverse Mercator (cylindrical) orLambert (conic)


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UTM

Worldwide system with units in meters

In northern hemisphere, Y-coordinate (northing) is

distance in meters from the Equator.

X-coordinate (easting) is distance in meters east from

a central meridian for a zone (negative values west ofthe central meridian).

Consists of 60 zones, each 6 degrees wide.


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State Plane Coordinates (SPCS)

Specific system for each state

Some states divided into multiple zones

with different grid systems for each zone.

Ohio has two zones: north and south

Most property maps (plat maps; tax maps),zoning maps, etc. are in State Plane

Coordinates.


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State Plane Coordinates - Units

NAD 27 - Coordinates in U.S. Survey Feet

NAD 83 - Coordinates Metric w/State Defined Foot Conversion

1 Meter = 3.280833333 U.S. Survey Feet

1 Meter = 3.280839895 International Feet

Difference is ~ 1:500,000U.S. Survey foot in Ohio


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STATE PLANE NORTH

STATE PLANE SOUTH

UTMZONE 16

UTMZONE 17

80818283848542

41

40

39

38

0

0

10 20 30 miles

10 20 30 40 kilometers

N

LATITUDE-LONGITUDE GRID, UTM ZONE BOUNDARY, ANDSTATE PLANE COORDINATE SYSTEM ZONE BOUNDARY

STATE OF OHIO DEPARTMENT OF NATURAL RESOURCES DIVISION OF GEOLOGICAL SURVEYBob Taft, Governor Samuel W. Speck, Director Thomas M. Berg, Chief

WILLIAMS FULTON LUCAS

OTTAWA

WOOD

HENRY

DEFIANCE

HARDIN

HANCOCK

AUGLAIZE

ALLEN

PUTNAM

MERCER

VAN WERT

PAULDING

HOLMES

ERIESANDUSKY

SENECAHURON

LORAIN

MEDINA

WAYNEASHLANDRICHLANDCRAWFORD

MORROW

WYANDOT

MARION

CARROLL

STARK COLUMBIANA

MAHONING

TRUMBULL

PORTAGE

SUMMIT

GEAUGA

ASHTABULA

LAKE

CUYAHOGA

UNION

DELAWARE

KNOX

COSHOCTON

TUSCARAWAS

HARRISON

JEFFERSON

FAYETTE

PICKAWAY

FRANKLINMADISON

CLARK

MONTGOMERYPREBLE

CHAMPAIGN

MIAMI

LOGAN

SHELBY

DARKE

BROWN

HIGHLAND

GREENE

CLINTONWARREN

CLERMONTHAMILTON

BUTLER

BELMONTGUERNSEY

NOBLE

MONROE

MUSKINGUM

MORGAN

WASHINGTON

LICKING

PERRYFAIRFIELD

HOCKING

ATHENS

MEIGS

VINTON

JACKSON

GALLIA

LAWRENCE

ROSS

PIKE

ADAMS

SCIOTO


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GEOGRAPHIC POSITION (LatGEOGRAPHIC POSITION (Lat--Long)Long)

Variation Between Datums: NAD27Variation Between Datums: NAD27

vsvs

NAD83NAD83

1927 North American DatumTo place on the predicted North American Datum 1983move the projection lines 4 meters south and

6 meters west as shown by dashed corner ticks.


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NAD 27 and NAD 83Two Horizontal Datums


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NAD 27 to NAD 83 (1986) Position and Coordinate Shifts

Geodetic vs State Plane

CLARK 1928

Geodetic Position

Latitude Longitude

NAD 27 40 03 09.89400 82 58 35.2650NAD 83 (1986) 40 03 10.12158 82 58 34.92303Difference -0.22758 -0.34197

North 23.06 ft East 25.17 ft

Overall position shift of 34.14 ft NE

State Plane Coordinates

Northing (Y) Easting (X)NAD 27 748,005.80 ft 1,866,612.19 ftNAD 83 (1986) 748,034.32 ft 1,835,142.41 ft

Difference + 37.52 ft - 31,469.78 ft

Overall shift is 6 miles East


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NGVD 29 and NAVD 88NGVD 29 and NAVD 88

Two VerticalTwo Vertical DatumsDatums


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Datum Transformation Software

Federally produced datum transformation software is

available free of charge from NOAAs National Geodetic

Survey.

http://www.ngs.noaa.gov/TOOLS/

NADCON NAD 83 vs NAD 27

VERTCON NAVD 88 vs NGVD 29

HTDP between a wide variety of reference frames

UTMS UTM vs lat/long

SPCS83 State Plane 83 vs lat/long

GPPCGP State Plane 27 vs lat/long

NATIONAL OCEAN SERVICE


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METADATA

METADATA IS DATA ABOUT DATA

DATUMS Horizontal including adjustment tagNAD 27, NAD 83(1986), NAD83 (199X), NGVD29, NAVD88

Geoid Model for GPS derived orthometric heights

GEOID96, GEOID99UNITS

Meters, U.S. Survey Feet, International Feet

ACCURACY

A, B, 1st, 2nd, 3rd

or 10 m, 1 m, 0.1 m, 3cm, 1cm


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http://www.ngs.noaa.gov/cgi-bin/datasheet.prl

National Geodetic Survey, Retrieval Date = MARCH 21, 2003KZ1585 ***********************************************************************KZ1585 DESIGNATION - SHANNAHANKZ1585 PID - KZ1585KZ1585 STATE/COUNTY- OH/DELAWAREKZ1585 USGS QUAD - POWELL (1988)KZ1585KZ1585 *CURRENT SURVEY CONTROLKZ1585 ___________________________________________________________________KZ1585* NAD 83(1995)- 40 09 24.94135(N) 083 00 26.03461(W) ADJUSTED

KZ1585* NAVD 88 - 296.307 (meters) 972.13 (feet) ADJUSTEDKZ1585 ___________________________________________________________________KZ1585 X - 594,316.727 (meters) COMPKZ1585 Y - -4,845,377.251 (meters) COMPKZ1585 Z - 4,091,487.584 (meters) COMPKZ1585 LAPLACE CORR- -3.19 (seconds) DEFLEC99KZ1585 ELLIP HEIGHT- 262.49 (meters) (04/01/98) GPS OBSKZ1585 GEOID HEIGHT- -33.85 (meters) GEOID99

KZ1585KZ1585 HORZ ORDER - FIRSTKZ1585 VERT ORDER - FIRST CLASS IKZ1585 ELLP ORDER - FOURTH CLASS I. . . . .KZ1585KZ1585; North East Units Scale Converg.KZ1585;SPC OH N - 54,568.670 556,782.294 MT 1.00006442 -0 19 59.6

KZ1585;SPC OH S - 239,579.155 556,783.904 MT 1.00002679 -0 19 18.7KZ1585;UTM 17 - 4,447,106.432 329,050.199 MT 0.99995976 -1 17 41.1KZ1585KZ1585 SUPERSEDED SURVEY CONTROLKZ1585KZ1585 NAD 83(1986)- 40 09 24.94900(N) 083 00 26.04100(W) AD( ) 1KZ1585 NAD 27 - 40 09 24.72300(N) 083 00 26.37800(W) AD( ) 1KZ1585 NGVD 29 - 296.464 (m) 972.65 (f) ADJ UNCH 1 1

KZ1585KZ1585.See file *dsdata.txt to determine how the superseded data were derived.

*dsdata.txt = Metadata for all datasheet information


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Good Geographical Information Systems

begin with good coordinates

GEOGRAPHY WITHOUT GEODESY IS A FELONY


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Adjustment tags

NAD83 has been readjusted periodically

with most states having 2 or 3adjustments with a final nationaladjustment planned in 2005.

Each time this happens a small number of

points are held fixed at the best valuesavailable at the time

In general each readjustment will result in

new coordinates for all points in theeffected area.

2005 Nationwide adjustment


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PLANE COORDINATE SYSTEMS

STATE PLANE AND UNIVERSIAL TRANSVERSE

MERCATOR GRID COORDINATES ARE A DIRECT

MATHEMATICAL CONVERSION FROM LATITUDE

AND LONGITUDE TO A CARTESIAN NORTHINGAND EASTING (Y & X) COORDINATE SYSTEM,

AND MUST MAINTAIN THE SAME DATUM TAG

[e.g. NAD 83(1993)] AS THE LATITUDE ANDLONGITUDE

NATIONAL OCEAN SERVICE


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STATE PLANE COORDINATE SYSTEMS

NOAA Manual NOS NGS - 5 State Plane Coordinate System of 1983

Lambert Conformal Conic and Transverse Mercator Projections

International, State and County Boundaries

Zones Approximately 158 miles wide

NAD 27 - Coordinates in U.S. Survey Feet

NAD 83 - Coordinates Metric w/State Defined Foot Conversion

1 Meter = 3.280833333 U.S. Survey Feet

1 Meter = 3.280839895 International Feet

U.S. Survey foot in Ohio


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Datums for GIS spatial references

All geodetic data has a datum and adjustment tagassociated with it

Ex: NAD83 (1995)

NAD83 (1986) SPC OH N

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