PDS_VERSION_ID                    = PDS3
RECORD_TYPE                       = STREAM
LABEL_REVISION_NOTE               = "S. Slavney, 2005-01-11
                                     J. Ward, 2006-08-23, edited to reflect
                                       current volume."
                                       
OBJECT                            = DATA_SET_MAP_PROJECTION
 DATA_SET_ID                      = "ARCB/NRAO-L-RTLS/GBT-4/5-70CM-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. Longitude 0 extends to the right, and Longitude 90 East extends
straight down from the center.

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

   X = (I - LINE_SAMPLES/2 - 0.5)/MAP_RESOLUTION
   Y = (J - LINES/2 - 0.5)/MAP_RESOLUTION

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

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

where

   I = sample coordinate
   J = line coordinate
   X,Y = I,J converted to Cartesian coordinate system with 0,0 at center
   MAP_RESOLUTION = the map resolution in pixels per degree
   LINE_SAMPLES = the total number of data instances along the horizontal
     axis of an image
   LINES = the total number of data instances along the vertical axis of an
     image
   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
   
"

  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