Post on 03-Apr-2018
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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 OhioDave.Conner@noaa.gov (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