CCSD3ZF0000100000001NJPL3IF0PDSX00000001 PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 SPACECRAFT_NAME = MAGELLAN TARGET_NAME = VENUS OBJECT = DATA_SET_MAP_PROJECTION DATA_SET_ID = "MGN-V-RDRS-5-DIM-V1.0" OBJECT = DATA_SET_MAP_PROJECTION_INFO MAP_PROJECTION_TYPE = "SINUSOIDAL" MAP_PROJECTION_DESC = "The FMAP (Magellan Full Resolution Radar Mosaic) is presented in a Sinusoidal Equal- Area map projection. In this projection, parallels of latitude are straight lines, with constant distances between equal latitude intervals. Lines of constant longitude on either side of the projection meridian are curved since longitude intervals decrease with the cosine of latitude to account for their convergence toward the poles. This projection offers a number of advantages for storing and managing global digital data; in particular, it is computationally simple, and data are stored in a compact form. The Sinusoidal Equal-Area projection is characterized by a projection longitude, which is the center meridian of the projection, and a scale, which is given in units of pixels/ degree. A projection longitude is defined for each FMAP; all tiles within the FMAP use the same projection longitude. The center latitude for all FMAPs is the equator. The transformation from latitude and longitude to line and sample is given by the following equations: line = INT(LINE_PROJECTION_OFFSET - lat*MAP_RESOLUTION + 1.0) sample = INT(SAMPLE_PROJECTION_OFFSET - (lon - CENTER_LONGITUDE)*MAP_RESOLUTION*cos(lat) + 1.0) Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given spot on the surface. LINE_PROJECTION_OFFSET is the line number minus one on which the map projection origin occurs. The map projection origin is the intersection of the equator and the projection longitude. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator. SAMPLE_PROJECTION_OFFSET is the nearest sample number to the left of the projection longitude. The value of SAMPLE_ PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude. CENTER_LONGITUDE is the value of the projection longitude, which is the longitude that passes through the center of the projection. MAP_RESOLUTION is measured in pixels/degree. FMAP products can have possible resolutions of 1408, 235, and 35. There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map. Definitions of other mapping parameters can be found in the PDS Data dictionary. **NOTE**: The FMAP CD-ROM volume set does not fully comply with PDS map projection standards. The line_projection_offset and sample_projection_offset keywords in the Image_Map_Projection Object of the FMAP products are set opposite to the way they are defined in the Planetary Science Data Dictionary (PSDD). The above equations for converting from lat/lon to line/sample are also in error. The correct equations are as follows: line = INT(LINE_PROJECTION_OFFSET - lat*MAP_RESOLUTION) sample = INT(SAMPLE_PROJECTION_OFFSET + (lon - CENTER_LONGITUDE)*MAP_RESOLUTION*cos(lat)) The value of 1.0 does not need to be added to either equation because the line_projection_offset and sample_projection_offset have already been translated to a (1,1) origin as defined in the PSDD. The equations were originally taken from the MDIM CD-ROM volume set which were not translated to a (1,1) origin. The equation for calculating the sample had a sign change because the direction of positive longitude is East instead of West as it was in the MDIM products. A software patch has been included on this disk to correct the line_projection_offset and sample_projection_offset keywords on FMAP products. The name of the program is PATCH and it is stored in the SOFTWARE directory. There is a version included for each of the platforms supported by this disk. PATCH is a command line driven program and can be run in either of the two following ways: patch from to patch from The from parameter is the name of an input FMAP image. The to parameter is the name of the output FMAP image with corrected label information. If you do not specify an output image file name, then the program will correct the labels in the input image file. You would probably only want to use both from and to parameters if you are correcting labels of images directly off of the CD-ROM. Please refer to the SOFTINFO.TXT file in the SOFTWARE directory for information on compiling and linking this program for different operating systems. The same commands used to compile and link the software described in that text file were used to create the executeable versions of the PATCH program on this disk." ROTATIONAL_ELEMENT_DESC = "See DAVIESETAL1989." OBJECT = DS_MAP_PROJECTION_REF_INFO REFERENCE_KEY_ID = "DAVIESETAL1989" END_OBJECT = DS_MAP_PROJECTION_REF_INFO OBJECT = DS_MAP_PROJECTION_REF_INFO REFERENCE_KEY_ID = "BATSON1987" END_OBJECT = DS_MAP_PROJECTION_REF_INFO OBJECT = DS_MAP_PROJECTION_REF_INFO REFERENCE_KEY_ID = "EDWARDS1987" 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