PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = DATA_SET_MAP_PROJECTION DATA_SET_ID = "N/A" OBJECT = DATA_SET_MAP_PROJECTION_INFO MAP_PROJECTION_TYPE = SINUSOIDAL MAP_PROJECTION_DESC = " 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/radian. The center latitude is the equator. The transformation from latitude and longitude (LAT,LON) in radians to LINE and SAMPLE is given by the following equations. SCALE = 3393400/MAP_SCALE LINE = LINE_PROJECTION_OFFSET-LAT*SCALE+0.5 SAMPLE = SAMPLE_PROJECTION_OFFSET + (LON-CENTER_LONGITUDE)*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. LINE_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 CENTER_LONGITUDE. For the sinusoidal projection, 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 image sample number to the left (west) of the projection longitude CENTER_LONGITUDE. For the sinusoidal projection, 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 typically the longitude that passes through the center of the projection. MAP_RESOLUTION number of pixels per degree at the projection origin." ROTATIONAL_ELEMENT_DESC = "See DAVIESETAL1989." OBJECT = DS_MAP_PROJECTION_REF_INFO REFERENCE_KEY_ID = "SNYDER1987" END_OBJECT = DS_MAP_PROJECTION_REF_INFO END_OBJECT = DATA_SET_MAP_PROJECTION_INFO OBJECT = DATA_SET_MAP_PROJECTION_INFO MAP_PROJECTION_TYPE = "SIMPLE CYLINDRICAL" MAP_PROJECTION_DESC = " In the simple cylindrical 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. Map resolution is constant throughout the image, thus increasing distortion away from the poles. The transformation from latitude and longitude (LAT, LON) in degrees to LINE and SAMPLE is given by the following equations. SCALE = MAP_RESOLUTION SAMPLE = SAMPLE_PROJECTION_OFFSET+SCALE*(LON-CENTER_LONGITUDE)+0.5 LINE = LINE_PROJECTION_OFFSET-SCALE*(LAT-CENTER_LATITUDE)+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 degrees. LINE_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 CENTER_LONGITUDE. SAMPLE_PROJECTION_OFFSET is the nearest image sample number to the left (west) of the projection longitude CENTER_LONGITUDE. CENTER_LONGITUDE is the value of the projection longitude in degrees, which is typically the longitude that passes through the center of the projection. MAP_RESOLUTION number of pixels per degree at the projection origin." ROTATIONAL_ELEMENT_DESC = "See DAVIESETAL1989." OBJECT = DS_MAP_PROJECTION_REF_INFO REFERENCE_KEY_ID = "SNYDER1987" END_OBJECT = DS_MAP_PROJECTION_REF_INFO END_OBJECT = DATA_SET_MAP_PROJECTION_INFO OBJECT = DATA_SET_MAP_PROJECTION_INFO MAP_PROJECTION_TYPE = STEREOGRAPHIC MAP_PROJECTION_DESC = " 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, with the central longitude (specified by the CENTER_LONGITUDE 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. The transformation from latitude and longitude (LAT, LON) in radians to LINE and SAMPLE is given by the following equations. SCALE = 3393400/MAP_SCALE North Polar Stereographic: SAMPLE = SAMPLE_PROJECTION_OFFSET + 2*SCALE*SIN(LON-CENTER_LONGITUDE)*TAN(PI/4-LAT/2)+0.5 LINE = LINE_PROJECTION_OFFSET + 2*SCALE*COS(LON-CENTER_LONGITUDE)*TAN(PI/4-LAT/2)+0.5 South Polar Stereographic: SAMPLE = SAMPLE_PROJECTION_OFFSET + 2*SCALE*SIN(LON-CENTER_LONGITUDE)*TAN(PI/4+LAT/2)+0.5 LINE = LINE_PROJECTION_OFFSET - 2*SCALE*COS(LON-CENTER_LONGITUDE)*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. LINE_PROJECTION_OFFSET is the image line number minus one on which the map projection origin occurs. The map projection origin is the appropriate pole. SAMPLE_PROJECTION_OFFSET is the nearest image sample number to the left (west) of the projection longitude CENTER_LONGITUDE. CENTER_LONGITUDE is the value of the projection longitude. MAP_SCALE pixel spacing at the projection origin, which is the appropriate pole for stereographic images. The value is in units of kilometers/pixel. MAP_RESOLUTION number of pixels per degree at the projection origin, which is the appropriate pole for stereographic images." ROTATIONAL_ELEMENT_DESC = "See DAVIESETAL1989." OBJECT = DS_MAP_PROJECTION_REF_INFO REFERENCE_KEY_ID = "SNYDER1987" END_OBJECT = DS_MAP_PROJECTION_REF_INFO END_OBJECT = DATA_SET_MAP_PROJECTION_INFO OBJECT = DATA_SET_MAP_PROJECTION_INFO MAP_PROJECTION_TYPE = MERCATOR MAP_PROJECTION_DESC = " 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). The transformation from latitude and longitude (LAT, LON) in radians to LINE and SAMPLE is given by the following equations. SCALE = MAP_RESOLUTION*180/PI SAMPLE = SAMPLE_PROJECTION_OFFSET+SCALE*(LON-CENTER_LONGITUDE)+0.5 LINE = LINE_PROJECTION_OFFSET-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. LINE_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 CENTER_LONGITUDE. For the Mercator projection, 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 image sample number to the left (west) of the projection longitude CENTER_LONGITUDE. For the Mercator projections, 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 in radians, which is typically the longitude that passes through the center of the projection. MAP_RESOLUTION number of pixels per degree at the projection origin, which is latitude=0, longitude=0 for Mercator images." ROTATIONAL_ELEMENT_DESC = "See DAVIESETAL1989." 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