Each recognized grid mapping is described in one of the sections
below. Each section contains: the valid name that is used with the
grid_mapping_name
attribute; a list of the specific
attributes that may be used to assign values to the mapping's parameters;
the standard names used to identify the coordinate variables that contain
the mapping's independent variables; and references to the mapping's
definition or other information that may help in using the mapping. Since
the attributes used to set a mapping's parameters may be shared among
several mappings, their definitions are contained in a table in the final
section. The attributes which describe the
ellipsoid and prime meridian may be included, when applicable, with any grid
mapping.
We have used the FGDC "Content Standard for Digital Geospatial
Metadata" [FGDC] as a guide in choosing the values for
grid_mapping_name
and the attribute names for the
parameters describing map projections.
grid_mapping_name
= albers_conical_equal_area
standard_parallel
 There may be 1 or
2 values.
longitude_of_central_meridian
latitude_of_projection_origin
false_easting
false_northing
The x (abscissa) and y (ordinate) rectangular coordinates are
identified by the standard_name
attribute values
projection_x_coordinate
and
projection_y_coordinate
respectively.
Notes on using the PROJ.4
software package
for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/albers_equal_area_conic.html.
grid_mapping_name
= azimuthal_equidistant
longitude_of_projection_origin
latitude_of_projection_origin
false_easting
false_northing
The x (abscissa) and y (ordinate) rectangular coordinates
are identified by the standard_name
attribute
values projection_x_coordinate
and
projection_y_coordinate
respectively.
Notes on using the PROJ.4
software
package for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/azimuthal_equidistant.html.
grid_mapping_name
= lambert_azimuthal_equal_area
longitude_of_projection_origin
latitude_of_projection_origin
false_easting
false_northing
The x (abscissa) and y (ordinate) rectangular coordinates
are identified by the standard_name
attribute
values projection_x_coordinate
and
projection_y_coordinate
respectively.
Notes on using the PROJ.4
software
package for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/lambert_azimuthal_equal_area.html.
grid_mapping_name
= lambert_conformal_conic
standard_parallel
 There may be 1
or 2 values.
longitude_of_central_meridian
latitude_of_projection_origin
false_easting
false_northing
The x (abscissa) and y (ordinate) rectangular coordinates
are identified by the standard_name
attribute
values projection_x_coordinate
and
projection_y_coordinate
respectively.
Notes on using the PROJ.4
software
package for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/lambert_conic_conformal_2sp.html.
grid_mapping_name
= lambert_cylindrical_equal_area
longitude_of_central_meridian
standard_parallel
or
scale_factor_at_projection_origin
false_easting
false_northing
The x (abscissa) and y (ordinate)
rectangular coordinates are identified by the
standard_name
attribute value
projection_x_coordinate
and
projection_y_coordinate
respectively.
Notes on using the PROJ.4 software packages for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/cylindrical_equal_area.html ("Lambert Cylindrical Equal Area" or EPSG 9834 or EPSG 9835). Detailed formulas can be found in [Snyder] pages 7685.
grid_mapping_name
= latitude_longitude
This grid mapping defines the canonical 2D geographical coordinate system based upon latitude and longitude coordinates on a spherical Earth. It is included so that the figure of the Earth can be described.
None.
The rectangular coordinates are longitude and latitude identified by the usual conventions (Section 4.1, “Latitude Coordinate” and Section 4.2, “Longitude Coordinate”).
grid_mapping_name
= mercator
longitude_of_projection_origin
standard_parallel
(EPSG 9805) or
scale_factor_at_projection_origin
(EPSG
9804)false_easting
false_northing
The x (abscissa) and y (ordinate)
rectangular coordinates are identified by the
standard_name
attribute value
projection_x_coordinate
and
projection_y_coordinate
respectively.
Notes on using the PROJ.4 software packages for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/mercator_1sp.html ("Mercator (1SP)" or EPSG 9804) or http://www.remotesensing.org/geotiff/proj_list/mercator_2sp.html ("Mercator (2SP)" or EPSG 9805).
More information on formulas available in [OGP/EPSG_GN7_2].
grid_mapping_name
= orthographic
longitude_of_projection_origin
latitude_of_projection_origin
false_easting
false_northing
The x (abscissa) and y (ordinate)
rectangular coordinates are identified by the
standard_name
attribute value
projection_x_coordinate
and
projection_y_coordinate
respectively.
Notes on using the PROJ.4 software packages for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/orthographic.html ("Orthographic" or EPSG 9840).
More information on formulas available in [OGP/EPSG_GN7_2].
grid_mapping_name
= polar_stereographic
straight_vertical_longitude_from_pole
latitude_of_projection_origin

Either +90. or 90.
Either standard_parallel
or
scale_factor_at_projection_origin
false_easting
false_northing
The x (abscissa) and y (ordinate) rectangular coordinates are
identified by the standard_name
attribute values
projection_x_coordinate
and
projection_y_coordinate
respectively.
Notes on using the PROJ.4
software package
for computing the mapping may be found at http://www.remotesensing.org/geotiff/proj_list/polar_stereographic.html.
grid_mapping_name
= rotated_latitude_longitude
grid_north_pole_latitude
grid_north_pole_longitude
north_pole_grid_longitude
 This
parameter is option (default is 0).
The rotated latitude and longitude coordinates are
identified by the standard_name
attribute
values grid_latitude
and
grid_longitude
respectively.
grid_mapping_name
= stereographic
longitude_of_projection_origin
latitude_of_projection_origin
scale_factor_at_projection_origin
false_easting
false_northing
The x (abscissa) and y (ordinate) rectangular coordinates
are identified by the standard_name
attribute
values projection_x_coordinate
and
projection_y_coordinate
respectively.
Formulas for the mapping and its inverse along with notes on
using the PROJ.4
software package for doing the
calcuations may be found at http://www.remotesensing.org/geotiff/proj_list/stereographic.html.
See the section "Polar stereographic" for the special case when
the projection origin is one of the poles.
grid_mapping_name
= transverse_mercator
scale_factor_at_central_meridian
longitude_of_central_meridian
latitude_of_projection_origin
false_easting
false_northing
The x (abscissa) and y (ordinate) rectangular coordinates
are identified by the standard_name
attribute
values projection_x_coordinate
and
projection_y_coordinate
respectively.
Formulas for the mapping and its inverse along with notes on
using the PROJ.4
software package for doing the
calcuations may be found at http://www.remotesensing.org/geotiff/proj_list/transverse_mercator.html.
grid_mapping_name
= vertical_perspective
latitude_of_projection_origin
longitude_of_projection_origin
perspective_point_height
false_easting
false_northing
The x (abscissa) and y (ordinate)
rectangular coordinates are identified by the
standard_name
attribute value
projection_x_coordinate
and
projection_y_coordinate
respectively.
Notes on using the
PROJ.4
software packages for computing the
mapping may be found at http://www.remotesensing.org/geotiff/proj_list/geos.html
. These notes assume the point of perspective is directly over the
equator. A more general description of vertical perspective
projection is given in [Snyder], pages 169181.
In the following table the "Type" values are S for string and N for numeric.
Table F.1. Grid Mapping Attributes
Attribute  Type  Description 

crs_wkt
 S  This optional attribute may be used to specify multiple coordinate system properties in wellknown text (WKT) format. The syntax must conform to the WKT format as specified in reference [[OGC_CTS]]. Use of the crs_wkt attribute is described in section 5.6.1. 
earth_radius
 N  Used to specify the radius, in metres, of the spherical figure used to approximate the shape of the Earth. This attribute should be specified for those projected coordinate reference systems in which the XY cartesian coordinates have been derived using a spherical Earth approximation. If the cartesian coordinates were derived using an ellipsoid, this attribute should not be defined. Example: "6371007", which is the radius of the GRS 1980 Authalic Sphere. 
false_easting
 N  The value added to all abscissa values in the rectangular
coordinates for a map projection. This value frequently is assigned
to eliminate negative numbers. Expressed in the unit of the
coordinate variable identified by the standard name
projection_x_coordinate . 
false_northing
 N  The value added to all ordinate values in the rectangular
coordinates for a map projection. This value frequently is assigned
to eliminate negative numbers. Expressed in the unit of the
coordinate variable identified by the standard name
projection_y_coordinate . 
grid_mapping_name
 S  The name used to identify the grid mapping. 
grid_north_pole_latitude
 N  True latitude (degrees_north) of the north pole of the rotated grid. 
grid_north_pole_longitude
 N  True longitude (degrees_east) of the north pole of the rotated grid. 
inverse_flattening
 N  Used to specify the inverse flattening (1/f) of the ellipsoidal figure associated with the geodetic datum and used to approximate the shape of the Earth. The flattening (f) of the ellipsoid is related to the semimajor and semiminor axes by the formula f = (ab)/a. In the case of a spherical Earth this attribute should be omitted or set to zero. Example: 298.257222101 for the GRS 1980 ellipsoid. (Note: By convention the dimensions of an ellipsoid are specified using either the semimajor and semiminor axis lengths, or the semimajor axis length and the inverse flattening. If all three attributes are specified then the supplied values must be consistent with the aforementioned formula.) 
latitude_of_projection_origin
 N  The latitude chosen as the origin of rectangular coordinates
for a map projection. Domain: 90.0 <=
latitude_of_projection_origin <= 90.0 
longitude_of_central_meridian
 N  The line of longitude at the center of a map projection
generally used as the basis for constructing the projection. Domain:
180.0 <= longitude_of_central_meridian <
180.0 
longitude_of_prime_meridian
 N 
Specifies the longitude, with respect to
Greenwich, of the prime meridian associated with the geodetic
datum. The prime meridian defines the origin from which longitude
values are determined. Not to be confused with the projection
origin longitude (cf.
longitude_of_projection_origin , a.k.a. central
meridian) which defines the longitude of the map projection
origin. Domain: 180.0 <= longitude_of_prime_meridian
< 180.0 decimal degrees. Default =
0.0

longitude_of_projection_origin
 N  The longitude chosen as the origin of rectangular coordinates
for a map projection. Domain: 180.0 <=
longitude_of_projection_origin < 180.0 
north_pole_grid_longitude
 N  Longitude (degrees) of the true north pole in the rotated grid. 
perspective_point_height
 N  Records the height, in metres, of the map projection perspective point above the ellipsoid (or sphere). Used by perspectivetype map projections, for example the Vertical Perspective Projection, which may be used to simulate the view from a Meteosat satellite. 
scale_factor_at_central_meridian
 N  A multiplier for reducing a distance obtained from a map by
computation or scaling to the actual distance along the central
meridian. Domain: scale_factor_at_central_meridian >
0.0 
scale_factor_at_projection_origin
 N  A multiplier for reducing a distance obtained from a map by
computation or scaling to the actual distance at the projection
origin. Domain: scale_factor_at_projection_origin >
0.0 
semi_major_axis
 N 
Specifies the length, in
metres, of the semimajor axis of the ellipsoidal
figure associated with the geodetic datum and used to approximate
the shape of the Earth. Commonly denoted using the symbol
a. In the case of a spherical Earth
approximation this attribute defines the radius of the Earth. See
also the inverse_flattening
attribute.

semi_minor_axis
 N  Specifies the length, in metres, of the semiminor axis of the ellipsoidal figure associated with the geodetic datum and used to approximate the shape of the Earth. Commonly denoted using the symbol b. In the case of a spherical Earth approximation this attribute should be omitted (the preferred option) or else set equal to the value of the semi_major_axis attribute. See also the inverse_flattening attribute. 
standard_parallel
 N  Specifies the line, or lines, of
latitude at which the developable map projection surface (plane,
cone, or cylinder) touches the reference sphere or ellipsoid used to
represent the Earth. Since there is zero scale distortion along a
standard parallel it is also referred to as a "latitude of true
scale". In the situation where a conical developable surface
intersects the reference ellipsoid there are two standard parallels,
in which case this attribute can be used as a vector to record both
latitude values, with the additional convention that the standard
parallel nearest the pole (N or S) is provided first.
Line of constant latitude at which the
surface of the Earth and plane or developable surface intersect.
This attribute may be vector valued if two standard parallels are
specified. Domain: 90.0 <=
standard_parallel <= 90.0 
straight_vertical_longitude_from_pole
 N  The longitude to be oriented straight up from the North or
South Pole. Domain: 180.0 <=
straight_vertical_longitude_from_pole < 180.0 