MAP_PROJ_INIT

The MAP_PROJ_INIT function initializes a mapping projection (establishes the coordinate conversion mechanism for mapping points on a globe's surface to points on a plane), using either IDL's own map projections or map projections from the U.S. Geological Survey's General Cartographic Transformation Package (GCTP). GCTP version 2.0 is included with IDL.

Note: The !MAP system variable is unaffected by MAP_PROJ_INIT. To use the map projection returned by MAP_PROJ_INIT for direct or object graphics, use the MAP_PROJ_FORWARD and MAP_PROJ_INVERSE functions to convert longitude/latitude values into Cartesian (x, y) coordinates before visualization.

This routine is written in the IDL language. Its source code can be found in map_proj_init.pro in the lib subdirectory of the IDL distribution.

Example

See MAP_PROJ_FORWARD for an example of using this function.

Syntax

Result = MAP_PROJ_INIT( Projection [, ELLIPSOID=value] [, /GCTP] [, LIMIT=vector] [, /RADIANS] [, /RELAXED] )

Keywords/Projection Parameters: [, CENTER_AZIMUTH=value] [, CENTER_LATITUDE=value] [, CENTER_LONGITUDE=value] [, FALSE_EASTING=value] [, FALSE_NORTHING=value] [, HEIGHT=value] [, HOM_AZIM_LONGITUDE=value] [, HOM_AZIM_ANGLE=value] [, HOM_LATITUDE1=value] [, HOM_LATITUDE2=value] [, HOM_LONGITUDE1=value] [, HOM_LONGITUDE2=value] [, IS_ZONES=value] [, IS_JUSTIFY=value] [, MERCATOR_SCALE=value] [, OEA_ANGLE=value] [, OEA_SHAPEM=value] [, OEA_SHAPEN=value] [, ROTATION=value] [, SEMIMAJOR_AXIS=value] [, SEMIMINOR_AXIS=value] [, SOM_INCLINATION=value] [, SOM_LONGITUDE=value] [, SOM_PERIOD=value] [, SOM_RATIO=value] [, SOM_FLAG=value] [, SOM_LANDSAT_NUMBER=value] [, SOM_LANDSAT_PATH=value] [, SPHERE_RADIUS=value] [, STANDARD_PARALLEL=value] [, STANDARD_PAR1=value] [, STANDARD_PAR2=value] [, SAT_TILT=value] [, TRUE_SCALE_LATITUDE=value] [, ZONE=value]

Return Value

The result is a !MAP structure containing the map parameters, which can be used as input to the map transformation functions MAP_PROJ_FORWARD and MAP_PROJ_INVERSE.

Arguments

Projection

Set this argument to either a projection index or a scalar string containing the name of the map projection, as described in following tables.

IDL projections:

#

Projection Name

Available Ellipsoids

Allowed Keyword Parameters

1

Stereographic

Sphere

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

2

Orthographic

Sphere

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

3

Lambert Conic

Sphere

SPHERE_RADIUS, STANDARD_PAR1, STANDARD_PAR2, CENTER_LONGITUDE, CENTER_LATITUDE

4

Lambert Azimuthal

Sphere

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

5

Gnomonic

Sphere

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

6

Azimuthal Equidistant

Sphere

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

7

Satellite

Sphere

SPHERE_RADIUS, HEIGHT, SAT_TILT, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

8

Cylindrical

Sphere

SPHERE_RADIUS, CENTER_AZIMUTH, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

9

Mercator

Sphere

SPHERE_RADIUS, CENTER_AZIMUTH, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

10

Mollweide

Sphere

SPHERE_RADIUS, CENTER_AZIMUTH, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

11

Sinusoidal

Sphere

SPHERE_RADIUS, CENTER_AZIMUTH, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

12

Aitoff

Sphere

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

13

Hammer Aitoff

Sphere

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

14

Albers Equal Area Conic

Sphere

SPHERE_RADIUS, STANDARD_PAR1, STANDARD_PAR2, CENTER_LONGITUDE, CENTER_LATITUDE

15

Transverse Mercator

All

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, MERCATOR_SCALE, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

16

Miller Cylindrical

Sphere

SPHERE_RADIUS, CENTER_AZIMUTH, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

17

Robinson

Sphere

SPHERE_RADIUS, CENTER_AZIMUTH, CENTER_LONGITUDE, CENTER_LATITUDE, ROTATION

18

Lambert Ellipsoid Conic

All

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, STANDARD_PAR1, STANDARD_PAR2, CENTER_LONGITUDE, CENTER_LATITUDE

19

Goodes Homolosine

Sphere

SPHERE_RADIUS, CENTER_LONGITUDE

GCTP projections:

#

Name

Allowed Map Parameters

Notes

100

Geographic

CENTER_LONGITUDE

No projection.

101

UTM

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, CENTER_LONGITUDE, CENTER_LATITUDE, ZONE

All ellipsoids; cylindrical; conformal; scale is reduced along the central longitude (MERCATOR_SCALE=0.9996).

102

State Plane

ZONE

"Clarke 1866" or "GRS 1980" ellipsoid; uses either Transverse Mercator, Lambert Conformal Conic, or Hotine Oblique Mercator.

103

Albers Equal Area

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, STANDARD_PAR1, STANDARD_PAR2, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; conic; equal-area; scale is true along the two standard parallels.

104

Lambert Conformal Conic

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, STANDARD_PAR1, STANDARD_PAR2, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; conformal; scale is true along the two standard parallels.

105

Mercator

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, CENTER_LONGITUDE, TRUE_SCALE_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; cylindrical; conformal; scale is true along the true scale latitudes.

106

Polar Stereographic

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, CENTER_LONGITUDE, TRUE_SCALE_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; azimuthal; conformal; scale is true along the true scale latitude.

107

Polyconic

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; neither conformal nor equal-area; scale is true along all parallels and along the central meridian.

108

Equidistant Conic

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, STANDARD_PARALLEL, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; equidistant; scale is true along all meridians and along one standard parallel.

208

Equidistant Conic

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, STANDARD_PAR1, STANDARD_PAR2, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; equidistant; scale is true along all meridians and along two standard parallels.

109

Transverse Mercator

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, MERCATOR_SCALE, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; cylindrical; conformal; scale is true (or reduced) along the center longitude.

110

Stereographic

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; azimuthal; conformal; scale is true at the center; directions from the center are true.

111

Lambert Azimuthal

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; azimuthal; equal-area; scale is true at the center; directions from the center are true for spherical and polar ellipsoidal.

112

Azimuthal Equidistant

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; azimuthal; equidistant; distances measured from the center are true; directions from the center are true; scale is true at the center.

113

Gnomonic

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; also known as the Gnomic or Central projection; azimuthal and perspective; neither conformal nor equal-area; all great circles are straight lines; scale is true at the center; directions from the center are true.

114

Orthographic

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; azimuthal; neither conformal nor equal-area; scale is true in the direction of latitude lines for the polar aspect; directions from the center are true.

115

Near Side Perspective

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, HEIGHT, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids (default is Sphere); also known as the Vertical Perspective; azimuthal; neither conformal nor equal-area; scale is true at the center; directions from the center are true.

116

Sinusoidal

SPHERE_RADIUS, CENTER_LONGITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; pseudocylindrical; equal-area; scale is true along the central meridian and along all parallels.

117

Equirectangular

SPHERE_RADIUS, CENTER_LONGITUDE, TRUE_SCALE_LATITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; also known as equidistant cylindrical; neither conformal nor equal-area; scale is true along all meridians and along the true scale latitudes.

118

Miller Cylindrical

SPHERE_RADIUS, CENTER_LONGITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; neither conformal nor equal-area; scale is true along the equator.

119

Van der Grinten

SPHERE_RADIUS, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; neither conformal nor equal-area; scale is true along the equator.

120

Hotine Oblique Mercator

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, MERCATOR_SCALE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING, HOM_LONGITUDE1, HOM_LATITUDE1, HOM_LONGITUDE2, HOM_LATITUDE2

All ellipsoids; cylindrical; conformal; scale is true (or reduced) along the center line. Specified using two lat-lon points.

220

Hotine Oblique Mercator

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, MERCATOR_SCALE, HOM_AZIM_ANGLE, HOM_AZIM_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; cylindrical; conformal; scale is true (or reduced) along the center line. Specified using azimuthal angle and longitude of the center.

121

Robinson

SPHERE_RADIUS, CENTER_LONGITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; pseudocylindrical; neither conformal nor equal-area; scale is true along the 38° parallels.

122

Space Oblique Mercator

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, SOM_INCLINATION, SOM_LONGITUDE, FALSE_EASTING, FALSE_NORTHING, SOM_PERIOD, SOM_RATIO, SOM_FLAG

All ellipsoids; modified cylindrical; basically conformal; scale is true along the groundtrack. Specified using inclination, longitude, period, ratio, and flag.

222

Space Oblique Mercator

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, SOM_LANDSAT_NUMBER, SOM_LANDSAT_PATH, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; modified cylindrical; basically conformal; scale is true along the groundtrack. Specified using landsat number and path.

123

Alaska Conformal

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; conformal; modified stereographic using complex algebra transformations to reduce scale variations.

124

Interrupted Goode

SPHERE_RADIUS

Sphere only; pseudocylindrical; equal-area; scale is true along the central meridians and along all parallels.

125

Mollweide

SPHERE_RADIUS, CENTER_LONGITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; pseudocylindrical; equal-area; scale is true along latitudes 40°44' N and S.

126

Interrupted Mollweide

SPHERE_RADIUS

Sphere only; pseudocylindrical; equal-area; scale is true along the 40°44' parallels.

127

Hammer

SPHERE_RADIUS, CENTER_LONGITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; also known as Hammer-Aitoff; based on Lambert Azimuthal; equal-area but not azimuthal; scale is true at the center.

128

Wagner IV

SPHERE_RADIUS, CENTER_LONGITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; pseudocylindrical; equal-area; scale is true along the 42°59' parallels.

129

Wagner VII

SPHERE_RADIUS, CENTER_LONGITUDE, FALSE_EASTING, FALSE_NORTHING

Sphere only; modification of the Hammer; equal-area; scale is true at the center.

130

Oblated Equal Area

SPHERE_RADIUS, OEA_SHAPEM, OEA_SHAPEN, CENTER_LONGITUDE, CENTER_LATITUDE, FALSE_EASTING, FALSE_NORTHING, OEA_ANGLE

Sphere only; equal-area; lines of constant distortion follow approximately oval or rectangular paths.

131

Integerized Sinusoidal

SPHERE_RADIUS, CENTER_LONGITUDE, FALSE_EASTING, FALSE_NORTHING, IS_ZONES, IS_JUSTIFY

Sphere only; equal-area; same as sinusoidal but with discrete latitude bands.

132

Cylindrical Equal Area

SEMIMAJOR_AXIS, SEMIMINOR_AXIS, CENTER_LONGITUDE, STANDARD_PARALLEL, FALSE_EASTING, FALSE_NORTHING

All ellipsoids; cylindrical; equal-area; scale is true along the standard parallels (special cases: Lambert 0°, Behrmann 30°, Trystan Edwards 37.383°, Peters 44.138°, Gall orthographic 45°, Balthasart 50°.
133 GOES-R SEMIMAJOR_AXIS, SEMIMINOR_AXIS, CENTER_LONGITUDE, HEIGHT, FALSE_EASTING, FALSE_NORTHING All ellipsoids (default is GRS 1980); same properties as Near Side Perspective but (x, y) coordinates are in scan-angle radians. Default height is 35786023 meters.

Keywords

Note: The following keywords apply to all projections.

ELLIPSOID

Set this keyword to either an integer code or a scalar string containing the ellipsoid name. The default value depends upon the projection selected, but is either the Clarke 1866 (ellipsoid 0), or a sphere of radius 6370.997 km (ellipsoid 19).

Note: For the GOES-R projection the default ellipsoid is GRS 1980.

The following ellipsoids are available for use with the ELLIPSOID keyword:

Index

Name

Semimajor axis (m)

Semiminor axis (m)

0

Clarke 1866

6378206.4

6356583.8

1

Clarke 1880

6378249.145

6356514.86955

2

Bessel

6377397.155

6356078.96284

3

International 1967

6378157.5

6356772.2

4

International 1909

6378388.0

6356911.94613

5

WGS 72

6378135.0

6356750.519915

6

Everest

6377276.3452

6356075.4133

7

WGS 66

6378145.0

6356759.769356

8

GRS 1980

6378137.0

6356752.31414

9

Airy

6377563.396

6356256.91

10

Modified Everest

6377304.063

6356103.039

11

Modified Airy

6377340.189

6356034.448

12

Walbeck

6378137.0

6356752.314245

13

Southeast Asia

6378155.0

6356773.3205

14

Australian National

6378160.0

6356774.719

15

Krassovsky

6378245.0

6356863.0188

16

Hough

6378270.0

6356794.343479

17

Mercury 1960

6378166.0

6356784.283666

18

Modified Mercury 1968

6378150.0

6356768.337303

19

Sphere

6370997.0

6370997.0

20

Clarke IGN

6378249.2

6356515.0

21

Helmert 1906

6378200.0

6356818.2

22

Modified Fischer 1960

6378155.0

6356773.3

23

South American 1969

6378160.0

6356774.7

24

WGS 84

6378137.0

6356752.314245

Note: For many projections, you can specify your own ellipsoid by using either the SEMIMAJOR_AXIS and SEMIMINOR_AXIS or the SPHERE_RADIUS keywords.

GCTP

Set this keyword to indicate that the GCTP library should be used for the projection. By default, MAP_PROJ_INIT uses the IDL projection library. This keyword is ignored if the projection exists only in one system (GCTP or IDL), or if the Projection argument is specified as an index.

LIMIT

Set this keyword to a four-element vector of the form

[Latmin, Lonmin, Latmax, Lonmax]

that specifies the boundaries of the region to be mapped. (Lonmin, Latmin) and (Lonmax, Latmax) are the longitudes and latitudes of two points diagonal from each other on the region's boundary.

Note: If the longitude range in LIMIT is less than or equal to 180 degrees, map clipping is performed in lat/lon coordinates before the transform. If the longitude range is greater than 180 degrees, map clipping is done in Cartesian coordinates after the transform. For non-cylindrical projections, clipping after the transformation to Cartesian coordinates means that some lat/lon points that fall outside the bounds specified by LIMIT may not be clipped. This occurs when the transformed lat/lon points fall inside the cartesian clipping rectangle.

Note: Lonmin should be in the range –180 to +180. Lonmax should be in the range –180 to +540, and must be greater than Lonmin. The total range for the map (Lonmax – Lonmin) must be 360 degrees or less.

RADIANS

Set this keyword to indicate that all parameters that represent angles are specified in radians rather than degrees.

RELAXED

If this keyword is set, any projection parameters which do not apply to the specified projection will be quietly ignored. By default, MAP_PROJ_INIT will issue errors for parameters that do not apply to the specified projection.

Projection Keywords

The following keywords apply only to some projections. Consult the tables above to determine which keywords apply to the projection you have selected.

Note: Unless the RADIANS keyword is set, all angles are measured in degrees, specified as a floating-point value.

CENTER_AZIMUTH

Set this keyword to the angle of the central azimuth, in degrees east of North. The default is 0 degrees. The pole is placed at an azimuth of CENTRAL_AZIMUTH degrees counterclockwise of North, as specified by the ROTATION keyword.

CENTER_LATITUDE

Set this keyword to the latitude of the point on the earth's surface to be mapped to the center of the projection plane. Latitude is measured in degrees North of the equator and must be in the range: -90 to +90. The default value is zero.

Note: For the GCTP UTM projection, the actual value of the center latitude is ignored, and only the sign (positive or negative) is used. If CENTER_LATITUDE is zero or greater then the UTM zone is positive (Northern hemisphere). If CENTER_LATITUDE is less than zero then the UTM zone is negative (Southern hemisphere). If ZONE is supplied then CENTER_LATITUDE is ignored.

Note: For the Hotine Oblique Mercator projection, the center latitude should not be set to 0, +90, or -90.

Note: For the GCTP Polar Stereographic projection, if the TRUE_SCALE_LATITUDE is greater than or equal to zero, the center latitude will automatically be set to +90 (the North pole). If the TRUE_SCALE_LATITUDE is less than zero, the center latitude will automatically be set to -90 (the South pole).

CENTER_LONGITUDE

Set this keyword to the longitude of the point on the earth's surface to be mapped to the center of the map projection. Longitude is measured in degrees east of the Greenwich meridian and must be in the range: -180 to +360. The default value is zero.

Note: For stereographic projections centered on the North or South pole, CENTER_LONGITUDE specifies the longitude directly below the pole.

Note: For the GCTP UTM projection, the center longitude is used to determine the UTM zone, along with the CENTER_LATITUDE to determine whether the zone is in the Northern or Southern hemisphere. If ZONE is supplied then CENTER_LONGITUDE is ignored.

FALSE_EASTING

Set this keyword to the false easting value (in meters) to be added to each x coordinate for the forward transform, or subtracted from each x coordinate for the inverse transform.

FALSE_NORTHING

Set this keyword to the false northing value (in meters) to be added to each y coordinate for the forward transform, or subtracted from each y coordinate for the inverse transform.

HEIGHT

Set this keyword to the height (in meters) above the earth's surface for satellite projections. The default values are:

HOM_AZIM_LONGITUDE

Set this keyword to the longitude in degrees of the central meridian point where the azimuth occurs.

HOM_AZIM_ANGLE

Set this keyword to the azimuth angle, measured in degrees, east of a north-south line that intersects the center line. The center line is defined as the great circle path along which the Mercator cylinder touches the sphere.

HOM_LATITUDE1

Set this keyword to the latitude in degrees of the first point on the center line. The center line is defined as the great circle path along which the Mercator cylinder touches the sphere.

Note: HOM_LATITUDE1 cannot be equal to HOM_LATITUDE2.

HOM_LATITUDE2

Set this keyword to the latitude in degrees of the second point on the center line. The center line is defined as the great circle path along which the Mercator cylinder touches the sphere.

Note: HOM_LATITUDE1 cannot be equal to HOM_LATITUDE2.

HOM_LONGITUDE1

Set this keyword to the longitude in degrees of the first point on the center line. The center line is defined as the great circle path along which the Mercator cylinder touches the sphere.

HOM_LONGITUDE2

Set this keyword to the longitude in degrees of the second point on the center line. The center line is defined as the great circle path along which the Mercator cylinder touches the sphere.

IS_ZONES

Set this keyword to the number of longitudinal zones to include in the projection.

IS_JUSTIFY

Set this keyword to a flag indicating what to do with rows with an odd number of columns. The possible values are:

0

Indicates the extra column is on the right of the projection Y axis

1

Indicates the extra column is on the left of the projection Y axis

2

Calculate an even number of columns

MERCATOR_SCALE

Set this keyword to the scale factor at the central meridian (Transverse Mercator projection) or the center of the projection (Hotine Oblique Mercator projection). For the Transverse Mercator projection, the default scale is 0.9996. For the UTM projection, the scale is fixed to 0.9996.

OEA_ANGLE

Set this keyword to the Oblated Equal Area oval rotation angle in degrees.

OEA_SHAPEM

Set this keyword to the Oblated Equal Area shape parameter m. The value of OEA_SHAPEM determines the horizontal flatness of the oblong region, and is usually set to a value between one and three.

OEA_SHAPEN

Set this keyword to the Oblated Equal Area oval shape parameter n. The value of OEA_SHAPEN determines the vertical flatness of the oblong region, and is usually set to a value between one and three.

Note: Setting both OEA_SHAPEM and OEA_SHAPEN equal to two is equivalent to using the Lambert Azimuthal projection.

ROTATION

Set this keyword to the angle through which the North direction should be rotated around the line between the earth's center and the point (CENTER_LONGITUDE, CENTER_LATITUDE). ROTATION is measured in degrees with the positive direction being clockwise rotation around the line. Values should be in the range ‑180 to +180. The default value is zero.

Note: If the center of the map is at the North pole, North is in the direction CENTER_LONGITUDE + 180. If the origin is at the South pole, North is in the direction CENTER_LONGITUDE.

SEMIMAJOR_AXIS

Set this keyword to the length (in meters) of the semimajor axis of the reference ellipsoid. The default is either the Clarke 1866 ellipsoid (6378206.4 m) or the Sphere radius (6370997 m), depending upon the projection.

SEMIMINOR_AXIS

Set this keyword to the length (in meters) of the semiminor axis of the reference ellipsoid. The default is either the Clarke 1866 ellipsoid (6356583.8 m) or the Sphere radius (6370997 m), depending upon the projection.

SOM_INCLINATION

Set this keyword to the orbit inclination angle in degrees of the ascending node, counter-clockwise from equator.

SOM_LONGITUDE

Set this keyword to the longitude in degrees of the ascending orbit at the equator.

SOM_PERIOD

Set this keyword to the period in minutes of the satellite revolution.

SOM_RATIO

Set this keyword to the Landsat ratio to compensate for confusion at the northern end of orbit. A typical value is 0.5201613.

SOM_FLAG

Set this keyword to the end of path flag for Landsat, where 0 is the start and 1 is the end.

SOM_LANDSAT_NUMBER

Set this keyword to the Landsat satellite number.

SOM_LANDSAT_PATH

Set this keyword to the Landsat path number (use 1 for Landsat 1, 2 and 3; use 2 for Landsat 4 and 5).

SPHERE_RADIUS

Set this keyword to the radius (in meters) of the reference sphere. The default is 6370997 m.

STANDARD_PARALLEL

Set this keyword to the latitude in degrees of the standard parallel along which the scale is true. The value must be between -90 and 90.

STANDARD_PAR1

Set this keyword to the latitude in degrees of the first standard parallel along which the scale is true. The value must be between -90 and 90.

Note: For Albers Equal Area and Lambert Conformal Conic projections, STANDARD_PAR1 and STANDARD_PAR2 should not be set to values that are equal and opposite.

STANDARD_PAR2

Set this keyword to the latitude in degrees of the second standard parallel along which the scale is true. The value must be between -90 and 90.

Note: For Albers Equal Area and Lambert Conformal Conic projections, STANDARD_PAR1 and STANDARD_PAR2 should not be set to values that are equal and opposite.

SAT_TILT

Set this keyword to the downward tilt in degrees of the camera, in degrees from the projection horizontal.

TRUE_SCALE_LATITUDE

Set this keyword to the latitude in degrees of true scale.

ZONE

Set this keyword to an integer giving the zone for the GCTP UTM projection or GCTP State Plane projection.

Note: For the UTM projection, you may also use the CENTER_LONGITUDE and CENTER_LATITUDE keywords to set the zone. Internally, the ZONE value will be computed from the longitude and latitude.

Note: For UTM, the zone number should be in the range -60 to -1 (Southern Hemisphere) or 1 to 60 (Northern Hemisphere).

The following table lists the allowed zones for the State Plane projection:

State

Jurisdiction Zone

NAD27 Zone Code

NAD83 Zone Code

Alabama

East

0101

0101

West

0102

0102

Alaska

01 through 10

5001 ... 5010

5001 ... 5010

Arizona

East

0201

0201

Central

0202

0202

West

0203

0203

Arkansas

North

0301

0301

South

0302

0302

California

01 through 07

0401 ... 0407

0401 ... 0406

Colorado

North

0501

0501

Central

0502

0502

South

0503

0503

Connecticut

0600

0600

Delaware

0700

0700

District of Columbia

1900

1900

Florida

East

0901

0901

West

0902

0902

North

0903

0903

Georgia

East

1001

1001

West

1002

1002

Hawaii

01 through 05

5101 ... 5105

5101 ... 5105

Idaho

East

1101

1101

Central

1102

1102

West

1103

1103

Illinois

East

1201

1201

West

1202

1202

Indiana

East

1301

1301

West

1302

1302

Iowa

North

1401

1401

South

1402

1402

Kansas

North

1501

1501

South

1502

1502

Kentucky

North

1601

1601

South

1602

1602

Louisiana

North

1701

1701

South

1702

1702

Offshore

1703

1703

Maine

East

1801

1801

West

1802

1802

Maryland

1900

1900

Massachusetts

Mainland

2001

2001

Island

2002

2002

Michigan

East (Transverse Mercator)

2101

-----

Central (Transverse Mercator)

2102

-----

West (Transverse Mercator)

2103

-----

North (Lambert)

2111

2111

Central (Lambert)

2112

2112

South (Lambert)

2113

2113

Minnesota

North

2201

2201

Central

2202

2202

South

2203

2203

Mississippi

East

2301

2301

West

2302

2302

Missouri

East

2401

2401

Central

2402

2402

West

2403

2403

Montana

-----

2500

 

North

2501

-----

Central

2502

-----

South

2503

-----

Nebraska

-----

2600

 

North

2601

-----

South

2602

-----

Nevada

East

2701

2701

Central

2702

2702

West

2703

2703

New Hampshire

2800

2800

New Jersey

2900

2900

New Mexico

East

3001

3001

Central

3002

3002

West

3003

3003

New York

East

3101

3101

Central

3102

3102

West

3103

3103

Long Island

3104

3104

North Carolina

3200

3200

North Dakota

North

3301

3301

South

3302

3302

Ohio

North

3401

3401

South

3402

3402

Oklahoma

North

3501

3501

South

3502

3502

Oregon

North

3601

3601

South

3602

3602

Pennsylvania

North

3701

3701

South

3702

3702

Rhode Island

3800

3800

South Carolina

-----

3900

 

North

3901

-----

South

3902

-----

South Dakota

North

4001

4001

South

4002

4002

Tennessee

4100

4100

Texas

North

4201

4201

North Central

4202

4202

Central

4203

4203

South Central

4204

4204

South

4205

4205

Utah

North

4301

4301

Central

4302

4302

South

4303

4303

Vermont

4400

4400

Virginia

North

4501

4501

South

4502

4502

Washington

North

4601

4601

South

4602

4602

West Virginia

North

4701

4701

South

4702

4702

Wisconsin

North

4801

4801

Central

4802

4802

South

4803

4803

Wyoming

East

4901

4901

East Central

4902

4902

West Central

4903

4903

West

4904

4904

Puerto Rico

5201

5200

Virgin Islands

-----

5200

 

St. John, St. Thomas

5201

-----

St. Croix

5202

-----

American Samoa

5300

-----

Guam

5400

-----

Version History

5.6

Introduced

7.1

Deprecated the DATUM keyword, added the ELLIPSOID keyword

8.0

Added Geographic and Cylindrical Equal Area projections, added ellipsoid support to Lambert Azimuthal

8.6.1

 Added ellipsoid support to Near Side Perspective projection; added GOES-R map projection.

See Also

MAP_PROJ_FORWARD, MAP_PROJ_INVERSE, MAP_PROJ_IMAGE