OBJECT = DATA_SET_MAP_PROJECT_CATALOG DATA_SET_ID = {"MGN-V-RDRS-5-GDR-EMISSIVITY-V1.0", "MGN-V-RDRS-5-GDR-REFLECTIVITY-V1.0", "MGN-V-RDRS-5-GDR-SLOPE-V1.0", "MGN-V-RDRS-5-GDR-TOPOGRAPHIC-V1.0"} OBJECT = DS_MAP_PROJECT_INFO_CATALOG MAP_PROJECTION_TYPE = SINUSOIDAL MAP_PROJECTION_DESC = " GxDR images are present in three map projections: sinusoidal, Mercator, and polar stereographic, using the Venus body-fixed coordinate system approved by the IAU in 1985 (see Davies, et al., 1989.) Each image is divided into an array of framelets, each of which is 1024 lines by 1024 samples. Each framelet is projected with the same mapping parameters so that a full GxDR image can be reconstructed by concatenating the framelets. In this case, the values of VICAR2 header keywords defining the projection (see below) should be taken from the first (top left) framelet. Browse images (named BROWSE.IMG) follow the same rules as their accompanying framelets, except that their headers don't contain the SUBF_ROW or SUBF_COL keywords. In the sinusoidal 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. 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. The center latitude for all GxDRs is the equator and the center meridian is the prime meridian. The transformation from latitude and longitude (LAT,LON) in radians to LINE and SAMPLE is given by the following equations. SCALE = 6051000/PIXSIZ LINE = SPECLINE-LAT*SCALE+0.5 SAMPLE = PROJSAMP+(LON-PROJ_LON)*SCALE*COS(LAT)+0.5 In the above definitions, integral values of LINE and SAMPLE correspond to the center of a pixel, and the top left image pixel has LINE=1 and SAMPLE=1. LAT and LON are the latitude and longitude of a given spot on the surface in radians. The other parameters in these equations are the names of keywords in the VICAR2 labels associated with each image. These parameters can also be found in the PDS labels of the image, but with different names. The values of parameters in the VICAR2 and PDS labels correspond to a given framelet. Thus, the computed LINE and SAMPLE relate to the framelet. The equivalent PDS keyword name is shown in parentheses. SPECLINE (X_AXIS_PROJECTION_OFFSET) is the image 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 PROJ_LON. For the sinusoidal projection, the value of SPECLINE is positive for images starting north of the equator and is negative for images starting south of the equator. PROJSAMP (Y_AXIS_PROJECTION_OFFSET) is the nearest image sample number to the left (west) of the projection longitude PROJ_LON. For the sinusoidal projection, the value of PROJSAMP 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. PROJ_LON (CENTER_LONGITUDE) is the value of the projection longitude, which is typically the longitude that passes through the center of the projection. PIXSIZ (MAP_SCALE) pixel spacing at the projection origin, which is latitude=0 for sinusoidal images, in which all pixels have the same spacing irrespective of latitude or longitude, The value in the VICAR2 label is in units of kilometers/pixel. PIXSIZ is 4.641 kilometers/pixel for all GxDRs. LAT_UC (MAXIMUM_LATITUDE) latitude of the center of the first framelet line. If the framelet contains no pixels that are within the sinusoidal projection, LAT_UC will be absent from the VICAR2 label and MAXIMUM_LATITUDE in the PDS label will be set to 'N/A'. LAT_LC (MINIMUM_LATITUDE) latitude of the center of the last framelet line. If the framelet contains no pixels that are within the sinusoidal projection, LAT_LC will be absent from the VICAR2 label and MINIMUM_LATITUDE in the PDS label will be set to 'N/A'. LON_CL (MINIMUM_LONGITUDE) the longitude of the leftmost pixel in the center framelet line. If the leftmost pixel lies outside the sinusoidal projection region, LON_CL will be omitted from the VICAR2 label and MINIMUM_LONGITUDE in the PDS label will be set to 180 degrees (or to 'N/A' if the framelet contains no pixels that are within the projection). LON_CR (MAXIMUM_LONGITUDE) the longitude of the rightmost pixel in the center framelet line. If the rightmost pixel lies outside the sinusoidal projection region, LON_CR will be omitted from the VICAR2 label and MAXIMUM_LONGITUDE in the PDS label will be set to 180 degrees (or to 'N/A' if the framelet contains no pixels that are within the projection). SUBF_COL (Y_AXIS_FRAMELET_OFFSET) column number of a framelet, which can have a value of 1 to 8. This keyword will be omitted in browse image headers. SUBF_ROW (X_AXIS_FRAMELET_OFFSET) row number of a framelet, which can have a value of 1 to 7. This keyword will be omitted in browse image headers. SCALE (MAP_RESOLUTION) number of pixels per degree at the projection origin, which is latitude=0, longitude=0 for sinusoidal images. SCALE is 22.75 pixels/degree for all GxDRs framelets. Definitions for the remaining parameters can be found in the GxDR Software Interface Specification document or the PDS Data Dictionary and in the file [DOCUMENT]GXDR.TXT on the GxDR CD-ROM. NOTE: The PDS keywords whose names begin 'X_' and 'Y_', e.g. X_AXIS_PROJECTION_OFFSET, Y_AXIS_PROJECTION_OFFSET, etc. use 'X' to denote LINE and 'Y' to denote SAMPLE. This is reversed relative to the definitions in Snyder (1987), i.e. x(Snyder) = y(PDS), and y(Snyder) = -x(PDS)." ROTATIONAL_ELEMENT_DESC = "See DAVIESETAL1989." OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = "DAVIESETAL1989" OBJECT = REFERENCE DOCUMENT_TOPIC_TYPE = "ROTATIONAL ELEMENTS OF THE PLANETS" JOURNAL_NAME = "CELESTIAL MECHANICS AND DYNAMICAL ASTRONOMY" PUBLICATION_DATE = 1989 REFERENCE_DESC = "Davies, M.E., V.K. Abalakin, M. Bursa, G.E. Hunt, J.H. Lieske, B. Morando, R.H. Rapp, P.K. Seidelmann, A.T. Sinclair, and Yu.S. Tyuflin, Report of the IAU/IAG/COSPAR working group on cartographic coordinates and rotational elements of the planets and satellites: 1988, Celestial Mechanics and Dynamical Astronomy, 46, 187-204, 1989." OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "MERTON E. DAVIES" END_OBJECT = REFERENCE_AUTHORS_CATALOG OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "V. K. ABALAKIN" END_OBJECT = REFERENCE_AUTHORS_CATALOG OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "M. BURSA" END_OBJECT = REFERENCE_AUTHORS_CATALOG OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "G. E. HUNT" END_OBJECT = REFERENCE_AUTHORS_CATALOG OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "J. H. LIESKE" END_OBJECT = REFERENCE_AUTHORS_CATALOG OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "B. MORANDO" END_OBJECT = REFERENCE_AUTHORS_CATALOG OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "R. H. RAPP" END_OBJECT = REFERENCE_AUTHORS_CATALOG OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "P. K. SEIDELMANN" END_OBJECT = REFERENCE_AUTHORS_CATALOG OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "A. T. SINCLAIR" END_OBJECT = REFERENCE_AUTHORS_CATALOG OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "Yu. S. TYUFLIN" END_OBJECT = REFERENCE_AUTHORS_CATALOG END_OBJECT = REFERENCE END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = "SNYDER1987" OBJECT = REFERENCE DOCUMENT_TOPIC_TYPE = "MAP PROJECTION" JOURNAL_NAME = "N/A" PUBLICATION_DATE = 1987 REFERENCE_DESC = "Snyder, John P., Map projections -- a working manual, U. S. Geol. Surv. Prof. Paper 1395, 383p., 1987." OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "JOHN P. SNYDER" END_OBJECT = REFERENCE_AUTHORS_CATALOG END_OBJECT = REFERENCE END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = "LYONS1988" OBJECT = REFERENCE DOCUMENT_TOPIC_TYPE = "MAGELLAN PLANETARY CONSTANTS AND MODELS" JOURNAL_NAME = "N/A" PUBLICATION_DATE = 1988 REFERENCE_DESC = "Lyons, D.T., Magellan Planetary Constants and Models, JPL D-2300, Jet Propulsion Laboratory, Pasadena, Calif., 1988." OBJECT = REFERENCE_AUTHORS_CATALOG AUTHOR_FULL_NAME = "D. T. LYONS" END_OBJECT = REFERENCE_AUTHORS_CATALOG END_OBJECT = REFERENCE END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG END_OBJECT = DS_MAP_PROJECT_INFO_CATALOG OBJECT = DS_MAP_PROJECT_INFO_CATALOG MAP_PROJECTION_TYPE = STEREOGRAPHIC MAP_PROJECTION_DESC = " GxDR images are present in three map projections: sinusoidal, Mercator, and polar stereographic, using the Venus body-fixed coordinate system approved by the IAU in 1985 (see Davies, et al., 1989.) Each image is divided into an array of framelets, each of which is 1024 lines by 1024 samples. Each framelet is projected with the same mapping parameters so that a full GxDR image can be reconstructed by concatenating the framelets. In this case, the values of VICAR2 header keywords defining the projection (see below) should be taken from the first (top left) framelet. Browse images (named BROWSE.IMG) follow the same rules as their accompanying framelets, except that their headers don't contain the SUBF_ROW or SUBF_COL keywords. In the polar stereographic projection, parallels of latitude are circles centered on the pole, and meridians of longitude are straight lines radiating from the pole. Images in this projection are centered on either the North or South pole of Venus, with the central longitude (specified by the 'PROJ_LON' value in the image label) running vertically from the pole to the bottom of the image for the North Polar projection, and to the top of the image for the South Polar projection, South polar GxDR images extend to 47S latitude and North polar GxDR images extend to 47N. The transformation from latitude and longitude (LAT,LON) in radians to LINE and SAMPLE is given by the following equations. SCALE = 6051000/PIXSIZ North Polar Stereographic: SAMPLE = PROJSAMP+2*SCALE*SIN(LON-PROJ_LON)*TAN(PI/4-LAT/2)+0.5 LINE = SPECLINE+2*SCALE*COS(LON-PROJ_LON)*TAN(PI/4-LAT/2)+0.5 South Polar Stereographic: SAMPLE = PROJSAMP+2*SCALE*SIN(LON-PROJ_LON)*TAN(PI/4+LAT/2)+0.5 LINE = SPECLINE-2*SCALE*COS(LON-PROJ_LON)*TAN(PI/4+LAT/2)+0.5 There is no explicit indication in the VICAR2 header itself as to whether the projection origin is the north or south pole. Software that must decide this automatically should examine the values of VICAR2 keywords LAT_UC and LAT_LC. If these are both positive, the origin is the north pole, if both negative it is the south pole. LAT_UC and LAT_LC will never be of opposite sign in GxDR image framelets. In the above definitions, integral values of LINE and SAMPLE correspond to the center of a pixel, and the top left image pixel has LINE=1 and SAMPLE=1. LAT and LON are the latitude and longitude of a given spot on the surface in radians. The other parameters in these equations are the names of keywords in the VICAR2 labels associated with each image. These parameters can also be found in the PDS labels of the image, but with different names. The values of parameters in the VICAR2 and PDS labels correspond to a given framelet. Thus, the computed LINE and SAMPLE relate to the framelet. The equivalent PDS keyword name is shown in parentheses. SPECLINE (X_AXIS_PROJECTION_OFFSET) is the image line number minus one on which the map projection origin occurs. The map projection origin is the appropriate pole. PROJSAMP (Y_AXIS_PROJECTION_OFFSET) is the nearest image sample number to the left (west) of the projection longitude PROJ_LON. PROJ_LON (CENTER_LONGITUDE) is the value of the projection longitude. PIXSIZ (MAP_SCALE) pixel spacing at the projection origin, which is the appropriate pole for stereographic images. The value in the VICAR2 label is in units of kilometers/pixel. PIXSIZ is 4.641 kilometers/pixel for all GxDRs. LAT_UC latitude of the center of the first framelet line. LAT_LC latitude of the center of the last framelet line. LON_CL the longitude of the leftmost pixel in the center framelet line. LON_CR the longitude of the rightmost pixel in the center framelet line. SUBF_COL (Y_AXIS_FRAMELET_OFFSET) column number of a framelet, which can have a value of 1 to 8. This keyword will be omitted in browse image headers. SUBF_ROW (X_AXIS_FRAMELET_OFFSET) row number of a framelet, which can have a value of 1 to 7. This keyword will be omitted in browse image headers. SCALE (MAP_RESOLUTION) number of pixels per degree at the projection origin, which is the appropriate pole for stereographic images. SCALE is 22.75 pixels/degree for all GxDRs framelets. In addition, the following PDS keywords have no precise equivalent in the VICAR2 labels: MINIMUM_LONGITUDE the westernmost longitude of any pixel in the framelet. MAXIMUM_LONGITUDE the easternmost longitude of any pixel in the framelet. MINIMUM_LATITUDE the southernmost latitude of any pixel in the framelet. MAXIMUM_LATITUDE the northernmost latitude of any pixel in the framelet. Definitions for the remaining parameters can be found in the GxDR Software Interface Specification document or the PDS Data Dictionary and in the file [DOCUMENT]GXDR.TXT on the GxDR CD-ROM. NOTE: The PDS keywords whose names begin 'X_' and 'Y_', e.g. X_AXIS_PROJECTION_OFFSET, Y_AXIS_PROJECTION_OFFSET, etc. use 'X' to denote LINE and 'Y' to denote SAMPLE. This is reversed relative to the definitions in Snyder (1987), i.e. x(Snyder) = y(PDS), and y(Snyder) = -x(PDS)." ROTATIONAL_ELEMENT_DESC = "See DAVIESETAL1989." OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = "DAVIESETAL1989" END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = "SNYDER1987" END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = "LYONS1988" END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG END_OBJECT = DS_MAP_PROJECT_INFO_CATALOG OBJECT = DS_MAP_PROJECT_INFO_CATALOG MAP_PROJECTION_TYPE = MERCATOR MAP_PROJECTION_DESC = " GxDR images are present in three map projections: sinusoidal, Mercator, and polar stereographic, using the Venus body-fixed coordinate system approved by the IAU in 1985 (see Davies, et al., 1989.) Each image is divided into an array of framelets, each of which is 1024 lines by 1024 samples. Each framelet is projected with the same mapping parameters so that a full GxDR image can be reconstructed by concatenating the framelets. In this case, the values of VICAR2 header keywords defining the projection (see below) should be taken from the first (top left) framelet. Browse images (named BROWSE.IMG) follow the same rules as their accompanying framelets, except that their headers don't contain the SUBF_ROW or SUBF_COL keywords. In the Mercator projection, parallels of latitude and meridians of longitude are straight lines that intersect one another at right angles. Images in this projection are centered on the equator. Pixel size decreases with increasing latitude in order to retain conformality (local preservation of shape). GxDR Mercator images extend from 66.5N latitude to 66.5S, and are centered at 60E longitude. The transformation from latitude and longitude (LAT,LON) in radians to LINE and SAMPLE is given by the following equations. SCALE = 6051000/PIXSIZ SAMPLE = PROJSAMP+SCALE*(LON-PROJ_LON)+0.5 LINE = SPECLINE-SCALE*LOG(TAN(PI/4+LAT/2))+0.5 In the above definitions, integral values of LINE and SAMPLE correspond to the center of a pixel, and the top left image pixel has LINE=1 and SAMPLE=1. LAT and LON are the latitude and longitude of a given spot on the surface in radians, and LOG is the natural logarithm function. The other parameters in these equations are the names of keywords in the VICAR2 labels associated with each image. These parameters can also be found in the PDS labels of the image, but with different names. The values of parameters in the VICAR2 and PDS labels correspond to a given framelet. Thus, the computed LINE and SAMPLE relate to the framelet. The equivalent PDS keyword name is shown in parentheses. SPECLINE (X_AXIS_PROJECTION_OFFSET) is the image 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 PROJ_LON. For the Mercator projection, the value of SPECLINE is positive for images starting north of the equator and is negative for images starting south of the equator. PROJSAMP (Y_AXIS_PROJECTION_OFFSET) is the nearest image sample number to the left (west) of the projection longitude PROJ_LON. For the Mercator projections, the value of PROJSAMP 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. PROJ_LON (CENTER_LONGITUDE) is the value of the projection longitude, which is typically the longitude that passes through the center of the projection. PIXSIZ (MAP_SCALE) pixel spacing at the projection origin, which is latitude=0 for Mercator images. The value in the VICAR2 label is in units of kilometers/pixel. PIXSIZ is 4.641 kilometers/pixel for all GxDRs. LAT_UC (MAXIMUM_LATITUDE) latitude of the first framelet line. LAT_LC (MINIMUM_LATITUDE) latitude of the last framelet line. LON_CL (MINIMUM_LONGITUDE) the longitude of the leftmost pixel in each line. LON_CR (MAXIMUM_LONGITUDE) the longitude of the rightmost pixel in each line. SUBF_COL (Y_AXIS_FRAMELET_OFFSET) column number of a framelet, which can have a value of 1 to 8. This keyword will be omitted in browse image headers. SUBF_ROW (X_AXIS_FRAMELET_OFFSET) row number of a framelet, which can have a value of 1 to 7. This keyword will be omitted in browse image headers. SCALE (MAP_RESOLUTION) number of pixels per degree at the projection origin, which is latitude=0, longitude=0 for Mercator images. SCALE is 22.75 pixels/degree for all GxDRs framelets. Definitions for the remaining parameters can be found in the GxDR Software Interface Specification document or the PDS Data Dictionary and in the file [DOCUMENT]GXDR.TXT on the GxDR CD-ROM. NOTE: The PDS keywords whose names begin 'X_' and 'Y_', e.g. X_AXIS_PROJECTION_OFFSET, Y_AXIS_PROJECTION_OFFSET, etc. use 'X' to denote LINE and 'Y' to denote SAMPLE. This is reversed relative to the definitions in Snyder (1987), i.e. x(Snyder) = y(PDS), and y(Snyder) = -x(PDS)." ROTATIONAL_ELEMENT_DESC = "See DAVIESETAL1989." OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = "DAVIESETAL1989" END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = "SNYDER1987" END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG REFERENCE_KEY_ID = "LYONS1988" END_OBJECT = DS_MAP_PROJ_REF_INFO_CATALOG END_OBJECT = DS_MAP_PROJECT_INFO_CATALOG END_OBJECT = DATA_SET_MAP_PROJECT_CATALOG END