Help for POLYPMAP

PURPOSE

    POLYPMAP converts coordinates for the specified map projection between
latitude-longitude space and line-sample space.

The following projections are currently implemented:

  Mercator					'MERCATOR
  Lambert Two-Standard Conformal Conic		'LAMBERT
  Cylindrical (Normal)				'CYLINDRI
  Simple Cylindrical (Rectangular)		'RECTANGU
  Polar Stereographic				'POLSTERE
  Oblique Stereographic 			'STEREOGR
  Polar Orthographic				'POLORTHO
  Oblique Orthographic 				'ORTHOGRA
  Oblique Simple Cylindrical 			'OBLICYL
  Sinusoidal Equal Area Projection  		'SINUSOID 
  Oblique Sinusoidal                            'OBSINUSO
  Mollweide                                     'MOLLWEID
  Transverse Mercator                           'TMERCATO

     The MIPL subroutine CONVEV (TRANV) is used to perform the map projections.
     POLYPMAP does not support "image space" or "object space".
     The results of the ported POLYPMAP  differ from the unported POLYPMAP
     in a few cases; (see under Precision and Accuracy).

EXECUTION

polypmap  INPUT.GRA OUTPUT.GRA  'projection    'mode     'placement      			PLANET=body              SCALE=pixel scale       			LATITUDE=special lat     LONGITUD=special long    			LINE=special line        SAMPLE=special sample   			PARAL1=first parallel    PARAL2=second parallel  			NORTHANG=north angle     'pole			 			LATRANGE=(minlat,maxlat) LONRANGE=(minlon,maxlon)  			SKIP=nominal data



    The map projection, the planet, and the scale must be specified.
    The MODE keyword is used to indicate the direction of the transformation;
the default is latitude-longitude to line-sample; use 'INVERSE for line-samp
to lat-long.
    The 'AUTOMAT keyword will cause the special line and sample to be
calculated so that latitudes and longitudes inside the LATRANGE,
LONRANGE box will project to a desired location.   'AUTO placement 
can only be used for a forward transformation.



EXAMPLES

polypmap  INPUT.GRA OUTPUT.GRA    'LAMBERT   'AUTOPLAC    			PLANET=MARS      SCALE=0.1     			LINE=10   SAMPLE=10		 			LATRANGE=(30,35)  LONRANGE=(10,15)   			PARAL1 = 35.83  PARAL2=59.17  



polypmap  INPUT.GRA OUTPUT.GRA    'MERCATOR    			PLANET=EARTH      SCALE=8.7     			LONGITUD=118    			LINE=500   SAMPLE=1000




NOTE: All latitudes and longitudes are in degrees, and all 
	longitudes are in West degrees (0 to 360).




    Projection Scaling
	In all map projections there is at least one point at which the scale
	of the projection equals the scale on the sphere. The scale at such
	points, in km/pixel, determines the size of the input picture in the
	output area. For the Mercator projection, scale is correct everywhere
	on the equator. For the Lambert, it is valid all along both standard
	parallels. For the Orthographic and Stereographic it is valid at the
	center of projection. (See also under Help for parameter PROJ.)


        Mercator Projection Parameters 
             LATITUDE    LONGITUD     LINE   SAMPLE     

        Lambert Projection Parameters
 	     LATITUDE    LONGITUD     PARAL1   PARAL2     LINE   SAMPLE

	Normal Cylindrical Parameters 
             LATITUDE    LONGITUD     LINE   SAMPLE     

	Simple Cylindrical (Rectangular) Projection Parameters
             LATITUDE    LONGITUD     LINE   SAMPLE     

        Polar Stereographic and Orthographic
	     LATITUDE    LONGITUD     POLE    LINE   SAMPLE
		
        Oblique Stereographic and Orthographic
	     LATITUDE   LONGITUD     NORTHANG    LINE   SAMPLE

	Oblique Simple Cylindrical
	     LATITUDE   LONGITUD     NORTHANG    LINE   SAMPLE

	Sinusoidal Equal Area Projection
             LONGITUD     LINE   SAMPLE     

	Oblique Sinusoidal Projection
             LATITUDE   LONGITUD     LINE   SAMPLE      PARAL1

        Mollweide Projection
             LONGITUD     LINE   SAMPLE     SCALE
       
        Transverse Mercator
             LATITUDE   LONGITUD     LINE   SAMPLE      SCALE
PRECISION AND ACCURACY

The unported POLYPMAP used a local version of the SUBLIB routine TRANV to do
coordinate transformations.  The ported POLYPMAP uses the SUBLIB routine 
CONVEV instead.  The change was made for the following reasons:
1) The local version of TRANV was ten years behind the SUBLIB version.  It was
   missing several corrections and several projection types.  Instead of
   using routine MERCPATCH for Mercator projections, this version of TRANV
   had one line commented out;  this appeared to be an inadequate substitute
   for MERCPATCH, giving different results.  There was nothing comparable
   to routine RECTPATCH in the local version of TRANV.
2) The use of local variants of SUBLIB routines makes VICAR maintenance more
   difficult.
3) Jean Lorre and Lucas Kamp said that TRANV was not intended for direct calls
   from application programs but was intended to be accessed via subroutine
   CONVEV.  

The results from the ported POLYPMAP differ from the unported POLYPMAP in
the following cases:
a) Mercator projection:  Because of the code differences described in 1) above,
   differences such as the following occur:
   Input lat,lon:       -60.73      -45.21
   Output line,samp
    from ported pgm     -24.04       51.33
   Output line,samp
    from unported pgm    86.65       51.33

b) Oblique simple cylindrical projection: The unported local version on TRANV
   appears to be in error, failing to convert THR1 to east longitude for the
   calculation of OLAMBDA.  The final equation for computing SAMPLE appears to
   be different.
   Differences such as the following occur:
   Input lat,lon:       -60.73      -45.21
   Output line,samp
    from ported pgm     -76.53     -134.44
   Output line,samp
    from unported pgm   -76.53      -54.67
c) Sinusoidal projection:  The computations in the ported TRANV have been
   overhauled, resulting in minor differences such as the following: 
   Input lat,lon:       -60.73      -45.21
   Output line,samp
    from ported pgm      -9.30       25.58
   Output line,samp
    from unported pgm    -9.44       25.69

PROGRAM HISTORY:
Original Programmer:    Frank Evans	May 1986
Cognizant Programmer:   Steve Pohorsky
Made portable for UNIX: Steve Pohorsky  Feb 1996
Revision:
  25 Jun 92  GMY  Added call to INIT_SPICE 70964
     Feb 96  SP   Ported to UNIX; now using SUBLIB routine CONVEV instead
                  of a local version of TRANV.  Works differently in a few
                  cases: see under Precision and Accuracy.

PARAMETERS: