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Map Projection Keywords - Meaning and Defaults

iproj=iproj, xsize=xsize, ysize=ysize, position=position, p0lat=p0lat, p0lon=p0lon, rot=rot, limit=limit, isotropic=isotropic, scale=scale, ellipsoid=ellipsoid, central_azimuth=central_azimuth, standard_parallels=standard_parallels, /CYLIN, /MERCATOR, /MOLLWEIDE, /STEREOGRAPHIC, /ORTHOGRAPHIC, /CONIC, /LAMBERT, /GNOMIC, /AZIMUTHAL, /SINUSOIDAL, /AITOFF, /HAMMER, /ALBERS, /MILLER, /TRANSVERSE_MERCATOR, /ROBINSON, /SATELLITE

The following keywords are included as attributes in the output SD. The default projection is /CYLINDRICAL or iproj=8.  Either the projection name or number can be used when specifying a projection method.
 

projection name	Keyword Projection /STEREO Stereographic /ORTHO Orthographic /CONIC Lambert's Conformal Conic /LAMBERT Lambert's Equal Area /GNOMIC Gnomic /AZIMUTHAL Azimuthal Equidistant /CYLIN Cylindrical Equidistant /MERCATOR Mercator /MOLLWEIDE Mollweide /SINUSOIDAL Sinusoidal /AITOFF Aitoff /ALBERS Alber's Equal Area Conic /HAMMER Hammer-Aitoff /TRANSVERSE_MERCATOR Transverse Mercator /MILLER Miller Cylindrical /ROBINSON Robinson /SATELLITE Satellite
iproj	Numeric value specifying a projection type.  Can be used instead of projection name keywords above.   iproj Value Projection Type 1 Stereographic 2 Orthographic 3 Lambert's Conic 4 Lambert 5 Gnomic 6 Azimuthal 7 Satellite 8 Cylindrical 9 Mercator 10 Mollweide 11 Sinusoidal 12 Aitoff 13 Hammer-Aitoff 14 Alber's Conic 15 Transverse Mercator 16 Miller Cylindrical 17 Robinson
xsize	The width of the output image size.  (Default=400)
ysize	The height of the output image size.  (Default=400)
position	The 4-element vector [(X0, Y0), (X1, Y1)] that defines the position of the mapped area within the output area defined by xsize and ysize.  The coordinates are in normalized units ranging from 0.0 to 1.0.  The default value is [0.0, 0.0, 1.0, 1.0] for specifying the map to fill the whole output array defined by xsize and ysize.
limit	The four-element vector [Latmin, Lonmin, Latmax, Lonmax] that specifies the boundaries of the region to be mapped.  The default limits are the boundaries of the input data file.
p0lat	The latitude of the point on the earth's surface to be mapped to the center of the projection plane.  The default used is projection-dependent.  In general, the default used will be the linear center of the latitude limits specified in limit.  For the following projections however, 0.0 is used as a default center: Cylindrical Mercator Mollweide Sinusoidal Transverse Mercator Miller Cylindrical Robinson
p0lon	The longitude of the point on the earth's surface to be mapped to the center of the projection plane.  The default used is projection-dependent.  In general, the default used will be the linear center of the longitude limits specified.  For the following projections however, 0.0 is used as a default center: Miller  Cylindrical
rot	The angle, measured in degrees, through which the North direction should be rotated around the line L between the earth's center and the point (p0lat, p0lon).  Default is 0.0 for all projections.
scale	Scale and limit are mutually exclusive.  If neither are specified explicitly, then the limit method is used. If scale is specified, then an isotropic map on the scale 1:scale will be produced to fit dimensions [xsize, ysize].  The resultant limits are implicit, are returned by the mapping algorithm and are stored in the output file as an SD attribute.
isotropic	Specify either ISOTROPIC=1 or /ISOTROPIC to produce a map that has the same scale in the X and Y direction.  The default mapping behavior is to produce a non-isotropic map in which the projection image is stretched to fit the output size specified by [xsize, ysize].
Projection-dependent keywords	Central Azimuth Scalar value.  The angle of the central azimuth in degrees east of north.  Only available for Cylindrical, Mercator, Miller, Mollweide and Sinusoidal projections.  The default is 0 degrees.  The pole is placed at an azimuth of CENTRAL_AZIMUTH degrees CCW of North, as specified by the Rot argument. Standard Parallels Only available for the 2 conic projections:  Lambert and Albers.  A one or two-element array defining the standard parallels for conic projections. Ellipsoid Only available for Transverse Mercator or Lambert Conic projections.  A 3-element array, [a, e^2, k], defining the ellipsoid.  The default is the Clarke 1866 ellipsoid, [6378206.4, 0.00676866, 0.9996]. a = equatorial radius in meters e^2 = eccentricity squared.  e^2 = 2 * f - f^2, where f = 1 - b/a (a: equatorial radius, b: polar radius; in meters). k = scale on the central meridian.