Command: projection

Syntax

projection <name>, <code> {,<origin>}

or

projection <name> = <ident>

Description

Create or redefine a projection identifier.

Parameters

• <name>
  The name of the projection identifier.

• <code>
  A string value containing a mnemonic code of one of the available projections. The list of available projection mnemonics are given below.

• <origin>
  The origin of the projection. This should be a longitude/latitude point in degrees. If omitted, a default typically (0,0) is used.

• <ident>
  Copy the attributes of an existing projection identifier into the new projection identifier. All command switches are ignored.

Switches

• -ang=<angle>
  A local 2-D transformation angle. When this switch is present all points in the projection are assumed to be rotated counterclockwise through angle. The pivot point for the rotation is the local origin (-loc).

• -dat=<point>
  A datum shift to be applied when converting between longlat and the projection. The system always assumes that longlat coordinates are based on positions on the WGS84 ellipsoid, and the datum shifts adjusts for differences in ellipsoid for local regions.

When this switch is omitted, longlat coordinates from and to this projection are assumed to be on the ellipsoid specified for the projection. If the ellipsoid specified for this projection is WGS84, this switch is redundant. The datum coordinates are assumed to be in the current modeling units (or the -un value).

• -ec=<num>
  The earth eccentricity (pole radius / equatorial radius). If omitted, it is computed automatically from other ellipsoid parameters.

• -eh=<num>
  The earth height (minor radius) in meters at the poles. If omitted, a radius derived from other ellipsoid parameters is used.

• -er=<num>
  The earth radius (in meters) at the equator. If omitted, a radius derived from other ellipsoid parameters is used.

• -g=<ellipsoid>
  A string containing a mnemonic code supplying the ellipsoid (earth model). If omitted, a sphere of earth radius 6370997 is assumed. The list of available ellipsoid mnemonics is given below.

• -lat=<nums>
  Provides one or more additional latitudes (applicable for some projections, e.g. conics). The values should be in degrees.

• -loc=<point>
  A local 2-D transformation origin shift. When this switch is present all points in the projection are assumed to be relative to this point (in projection space. Local rotation and scaling (-and -sc) are computed relative to this point. The coordinates are assumed to be in the current modeling units (or the -un value), but will be adjusted automatically on a subsequent change of modeling units.

• -rf=<num>
  The reciprocal flattening of the earth. If omitted, any flattening defined by the ellipsoid is used. If included, this resets the eccentricity.

• -s
  For some projections, e.g. the Universal Transverse Mercator projection, this indicates a South Hemisphere origin shift.

• -sc
  A local 2-D transformation scale factor. When this switch is present all points in the projection are assumed to be scaled by this factor. The pivot point for the scaling is the local origin (-loc).

• -un
  The units for the -loc and -dat values. If this switch is omitted, the current modeling units are assumed.

• -v=<num>
  A version number (necessary for some projections).

• -w=<num>
  An auxiliary weighting factor (necessary for some projections).

• -z=<num>
  A Universal Transverse Mercator zone number. This should have a value 1 through 60.

Notes

All projections provide a means of going from longitude/latitude to Cartesian space, but some do not have an inverse. These are marked as F (forward) and I (inverse) in the supplementary list of projection mnemonics.

Examples

projection amg55,'utm',-z=55,-s,-g='aust_ntl'

projection my55 = amg55

projection cassini,'cassini'

projection ukng,'tmercator',(-2,49),-loc=(-400000,100000),\ 
    -g='airy',-dat=(372,-111,426),-un='m',-w=0.999601

projection gauss_boaga_est,'tmercator',(9,0),-loc=(-2520000,0),\ 
    -g='ire09',-dat=(-87,-98,-121),-un='m',-w=0.9996

See Also

Projection Mnemonic Codes

• airy - Airy (F)

• -v=1 - cut at hemisphere limit

• -v=2 - not cut at hemisphere limit

• -lat=<num> - default 90

• aitoff - Aitoff (F)

• albers - Albers Equal Area (FI)

• -lat=<nums> - default 0,10

• apian - Apian Globular (F)

• august - August Epicycloidal (F)

• bacon - Bacon Globular (F)

• bipolar - Bipolar Conic (FI)

• boggs - Boggs Eumorphic (F)

• bonne - Bonne (FI)

• -lat=<numgt; - default 40

• cassini - Cassini (FI)

• collignon - Collignon (FI)

• centcyl - Central Cylindrical (FI)

• cyleqarea - Cylindrical Equal Area (FI)

• -lat=<num> - default 0

• dense - Denoyer Semi-Elliptical (F)

• eckert - Eckert (FI)

• -v=<num> - range 1 through 6, default is 1

• eisenlohr - Eisenlohr (F)

• eqd_azim - Equidistant Azimuthal (FI)

• -lat=<num> - default 0

• eqd_conic - Equidistant Conic (FI)

• -lat=<nums> - default 0,10

• eqd_cyl - Equidistant Cylindrical (FI)

• -lat=<num> - default 0

• fournier - Fournier Globular (F)

• gall - Gall Stereographic (FI)

• goode - Goode Homosoline (F)

• gnomonic - Gnomonic (FI)

• hammer - Hammer Elliptical (F)

• -w=<num> - weighting factor, default 0.5

• hatano - Hatano Asymmetrical Equal Area (FI)

• isg - Integrated Survey Grid (FI)

• -s - Southern Hemisphere (Australian System origin)

• -z=<num> - Zone number

• lagrange - Lagrange (F)

• -lat=<num> - default 0

• -w=<num> - weighting factor, default 2

• lazeqarea - Lambert Azimuthal Equal Area (FI)

• lcc - Lambert Conformal Conic (FI)

• -lat=<nums> - default 0,10

• leqarea - Lambert Equal Area Conic (FI)

• -lat=<num> - default 0

• -s - Southern Hemisphere

• loxim - Loximuthal (FI)

• -lat=<num> - default 0

• mcbryde - McBryde-Thomas (FI)

• -v=1 - Flat-Polar Parabolic (default)

• -v=2 - Flat-Polar Sinusoidal

• -v=3 - Flat-Polar Quartic

• mercator - Mercator (FI)

• -lat=<num> - default 0

• miller - Miller Cylindrical (FI)

• mollweide - Mollweide (FI)

• nicolosi - Nicolosi Globular (F)

• nzmg - New Zealand Mapping Grid (FI)

• ortelius - Ortelius (F)

• ortho - Orthographic (FI)

• parabolic - Craster Parabolic (FI)

• pconic - Perspective Conic (F)

• -lat=<nums> - default 0,10

• polyconic - Polyconic (American) (FI)

• putnins - Putnins (FI)

• -v=2 - P2 (default)

• -v=5 - P5

• quarth - Quartic Authalic (FI)

• rectpoly - Rectangular Polyconic (F)

• -lat=<num> - default 0

• robinson - Robinson (FI)

• sinusoidal - Sinusoidal (FI)

• stereo - Stereographic (FI)

• -lat=<num> - default 90

• -w=<num> - dk value, default 1

• tcc - Transverse Central Cylindrical (F)

• tcea - Transverse Cylindrical Equal Area (FI)

• tmercator - Transverse Mercator (FI)

• -w=<num> - scale factor, default 1

• up_stereo - Universal Polar Stereographic (FI)

• -s - Southern Hemisphere

• utm - Universal Transverse Mercator (FI)

• -s - Southern Hemisphere (Australian Mapping Grid origin)

• -z=<num> - Zone number

• van_der_grinten - Van der Grinten

• -v=1 - projection I (FI) (default)

• -v=2 - projection II (F)

• -v=3 - projection III (F)

• -v=4 - projection IV (F)

• wagner - Wagner VII (F)

• winkel - Winkel I (FI)

• -lat=<num> - default 0

• winkel_tripel - Winkel Tripel (F)

• -lat=<num> - default 0

Ellipsoid Mnemonic Codes

• null string - Default spheroid (er=6370997)

• airy - Airy 1830 (er=6377563.396, rf=299.3249646)

• ats77 - ATS 1977 (er=6378135, rf=298.257)

• aust_ntl - Australian Natl, IAU 64, South American 1969 (er=6378160, rf=298.25)

• bessel - Bessel 1841 (er=6377397.155, rf=299.1528128)

• bessel_nam - Bessel 1841 (Namibia) (er=6377483.865, rf=299.1528128)

• clrk66 - Clarke 1866 (er=6378206.4, rf=294.9786982)

• clrk80 - Clarke 1880 mod. (er=6378249.145, rf=293.465)

• everest - Everest (er=6377276.3452, eh=6356075.4133)

• everest_india_1830 - Everest (India 1830) (er=6377276.345, rf=300.8017)

• everest_india_1956 - Everest (India 1956) (er=6377301.243, rf=300.8017)

• everest_sabah - Everest (Sabah Sarawak) (er=6377298.556, rf=300.8017)

• everest_malay_1948 - Everest (Malaya & Singapore 1948) (er=6377304.063, rf=300.8017)

• everest_malay_1969 - Everest (Malaysia 1969) (er=6377295.664, rf=300.8017)

• everest_pakistan - Everest (Pakistan) (er=6377309.613, rf=300.8017)

• gda94 - Geocentric Datum of Australia (1994) (er=6378137, rf=298.2572221)

• grs67 - GRS 67 (IUGG 1967) (er=6378160, rf=247.247167)

• grs80 - GRS 1980 (IUGG, 1980) (er=6378137, rf=298.257222101)

• helmert - Helmert 1906 (er=6378200, rf=298.3)

• hough - Hough 1960 (er=6378270, rf=297)

• iau76 - IAU 1976 (er=6378140, rf=298.257)

• indonesia_1974 - Indonesian 1974 (er=6378160, rf=298.247)

• ire09 - International 1909 (Hayford), International 1924 (er=6378388, rf=297)

• ire67 - International 1967 (er=6378160, rf=297)

• krass - Krassovsky (er=6378245, rf=298.3)

• mercury - Mercury 1960 (er=6378166, eh=6356784.283666)

• merit - MERIT 1983 (er=6378137, rf=298.257)

• mod_airy - Modified Airy (er=6377340.189, rf=299.3249646)

• mod_ever - Modified Everest (er=6377304.063, eh=6356103.039)

• mod_fischer - Modified Fischer 1960 (er=6378155.063, rf=298.3)

• mod_merc - Modified Merc 1968 (er=6378150, eh=6356768.337303)

• new_intl - New International 1967 (er=6378157.5, eh=6356772.2)

• nwl_9d - NWL 9D (er=6378145, rf=298.25)

• seasia - Southeast Asia (er=6378155, eh=6356773.3205)

• walbeck - Walbeck (er=6376896, eh=6355834.8467)

• wgs66 - WGS 66 (er=6378145, eh=6356759.769356)

• wgs72 - WGS 72 (er=6378135, rf=298.26)

• wgs84 - WGS 84 (er=6378137, rf=298.257223563)