mappars Documentation

mappars - Extensive description of MAPPARS parameter
The purpose of this pdf is for reference only on the MAPPARS parameter
string that is used by many ISIS programs.  The MAPPARS parameter
string allows the user to specify a map projection and the parameters
needed to define the projection.

This pdf is not intended to be a tutorial on map projections.  For
detailed information on this subject you should read "Map Projections
-- A Working Manual, USGS Professional Paper 1395, by John Synder".


BASIC FORMAT:

        mappars = "proj:param1,param2,..."

   where,

	proj is an ISIS supported projection name (only enough of the
                projection name to uniquely identify it is needed)
   	param1 is a mapping parameter required for that projection
   	param2 is another mapping parameter required for that projection

   For example,

	mappars= "sinu:0"

   Indicates a sinusoidal map projection with a center longitude of
   zero.

   The mappars parameter may or may not have defaults.  This depends
   entirely upon the ISIS program.  For example, "lev1tolev2" will
   calculate defaults if the user does not enter the map projection
   parameters after the projection code (e.g., mappars = "sinu:").
   However, the program "lev2grid" requires the user completely enter
   the parameters for the projection.  The individual programs will
   indicate if they allow defaults for mappars parameter.  All
   programs which allow defaults are consistent in the way the
   defaults are determined.  Read the sections below to see how the
   defaults will be calculated.

SUPPORTED PROJECTIONS:

------------------------------------------------------------------------

Name:		SINUSOIDAL
                (aka Plate Carree, or sinusoidal_equal_area)
Equation:	Spherical
Form:		mappars = "sinu:clon,plattyp"
Parameters:	clon is the Longitude of Central Meridian
                plattyp is the projection latitude type
                        (OGRAPHIC or OCENTRIC)
Default:	clon defaults to the average of the longitude range and
                plattype defaults to OGRAPHIC
Example:	mappars = "sinu:0,OGRAPHIC"

------------------------------------------------------------------------

Name:		SIMPLE_CYLINDRICAL
Equation:	Spherical
Form:		mappars = "simp:clon,plattyp"
Parameters:	clon is the Longitude of Central Meridian
                plattyp is the projection latitude type
                        (OGRAPHIC or OCENTRIC)
Default:	clon defaults to the average of the longitude range and
                plattype defaults to OGRAPHIC
Example:	mappars = "simp:40,OGRAPHIC"

------------------------------------------------------------------------

Name:		MERCATOR	
Equation:	Ellipsoidal
Form:		mappars = "merc:clat,clon"
Parameters:	clat is the Latitude of True Scale	
		clon is the Longitude of Central Meridian
Default:	clat defaults to the average of the latitude range	
		clon defaults to the average of the longitude range
Example:	mappars = "merc:20,50"

------------------------------------------------------------------------

Name:		POLAR_STEREOGRAPHIC	
Equation:	Ellipsoidal
Form:		mappars = "pola:clat,clon"
Parameters:	clat is the Latitude of True Scale
		clon is the Longitude of the Y-axis
Default:	clat defaults to 90 if latitude range is positive
                     - or - to -90 if latitude range is negative
		clon defaults to the average of the longitude range
Example:	mappars = "pola:0,90"

------------------------------------------------------------------------

Name:		LAMBERT_CONFORMAL_CONIC	
Equation:	Ellipsoidal
Form:		mappars = "lamb:clat,clon,par1,par2"
Parameters:	clat is the Latitude of the origin of the projection
		clon is the Longitude of the origin of the projection
		par1 is the 1st standard parallel
		par2 is the 2nd standard parallel
Default:	Currently no defaults	
Example:	mappars = "lamb:0,0,30,45""

------------------------------------------------------------------------

Name:		EQUIRECTANGULAR_CYLINDRICAL
                  (aka Equidistant, Rectangular, or Simple
                   Cylindrical if clat = 0)
Equation:	Spherical
Form:		mappars = "equi:clat,clon,plattyp"
Parameters:	clat is the Latitude of True Scale	
		clon is the Longitude of Central Meridian
                plattyp is the projection latitude type
                        (OGRAPHIC or OCENTRIC)
Default:	clat defaults to the average of the latitude range	
		clon defaults to the average of the longitude range
                plattype defaults to OGRAPHIC
Example:	mappars = "equi:20,50,OGRAPHIC"

------------------------------------------------------------------------

Name:		ORTHOGRAPHIC
Equation:	Spherical
Form:		mappars = "orth:clat,clon"
Parameters:	clat is the center latitude
		clon is the center longitude
Default:	clat defaults to the average of the latitude range
		clon defaults to the average of the longitude range
Example:	mappars = "orth:0,180"

------------------------------------------------------------------------

Map projection and parameters
(e.g., MAPPARS="SINU:0")

NONE

ADDITIONAL NOTES:

Parm

Description

MAPPARS

MAPPARS specifies the desired output map projection and the required parameters to define that projection in a single string. The required parameters vary from projection to projection. Tutor mappars.pdf for a list of supported projections and their required projections. For more information on map projections see U.S.G.S. Professional paper 1395 titled "Map Projections - A Working Manual", by John Snyder.