PDS_VERSION_ID                    = PDS3
LABEL_REVISION_NOTE               = "S. SLAVNEY, 2005-01-11"
RECORD_TYPE                       = STREAM

OBJECT                            = DATA_SET_MAP_PROJECTION
 DATA_SET_ID                      = "MGS-M-MOLA-5-MEGDR-L3-V1.0"
 OBJECT                           = DATA_SET_MAP_PROJECTION_INFO
  MAP_PROJECTION_TYPE             = "POLAR STEREOGRAPHIC"
  MAP_PROJECTION_DESC             = "

In this polar stereographic projection [SNYDER1987], the projection is
centered on the north or south pole. Lines of longitude extend
radially from the center and parallels of latitude are concentric
circles around the center. In the north, Longitude 0 extends straight
down from the center and Longitude 90 East extends to the right.
In the south, Longitude 0 extends straight up from the center, and
Longitude 90 East extends to the right. An ellipsoid has been
adopted for Mars by the IAU with C=3376.2 and A=3396.19. The MOLA Team
has approximated the ellipsoidal projection by adopting a spherical
geometry with a polar radius of 3376.2 km, with a planetocentric
spacing of 2^n pixels per degree at the pole. This can be converted to
a nominal scale factor of 115.09 meters per pixel for 512 pixels per
degree, 230.18 meters per pixel for 256 pixels per degree, and 460.36
meters per pixel for 128 pixels per degree.

The transformation from line and sample coordinates to planetocentric
latitude and longitude is given by these equations.

   X = (I - N/2 - 0.5)/RES
   Y = (J - N/2 - 0.5)/RES

   R = SQRT(X^2 + Y^2)

   LON = ATAN2(X,Y) * 180/PI
   LAT = 90 - 2*ATAN(R*PI/360) * 180/PI (northern hemisphere)
   LAT = -90 + 2*ATAN(R*PI/360) * 180/PI (southern hemisphere)

where

   I = sample coordinate
   J = line coordinate
   X,Y = I,J converted to Cartesian coordinate system with 0,0 at center
   RES = the map resolution in pixels per degree
   N = the number of lines or samples per line in the image
       (the images are square)
   R = radius from center of map to pixel I,J
   LON = east longitude of pixel I,J in degrees
   LAT = latitude of pixel I,J in degrees

Values for RES and N can be found in the image label as the 
keywords MAP_RESOLUTION and LINES.

"

  ROTATIONAL_ELEMENT_DESC         = "See [SEIDELMANNETAL2002]."

  OBJECT                          = DS_MAP_PROJECTION_REF_INFO
   REFERENCE_KEY_ID               = "SEIDELMANNETAL2002"
  END_OBJECT                      = DS_MAP_PROJECTION_REF_INFO

  OBJECT                          = DS_MAP_PROJECTION_REF_INFO
   REFERENCE_KEY_ID               = "SNYDER1987"
  END_OBJECT                      = DS_MAP_PROJECTION_REF_INFO

 END_OBJECT                       = DATA_SET_MAP_PROJECTION_INFO
END_OBJECT                        = DATA_SET_MAP_PROJECTION

END