Data Set Information
DATA_SET_NAME VO1/VO2 MARS VISUAL IMAGING SUBSYSTEM DIGITAL TERRAIN MODEL
DATA_SET_ID VO1/VO2-M-VIS-5-DTM-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This digital image map of Mars is a cartographic extension of a previously released set of CDROM volumes containing individual Viking Orbiter Images (PDS volumes VO_1001, VO_1002, etc.). The data in the latter are pristine, in the sense that they were processed only to the extent required to view them as images. They contain the artifacts and the radiometric, geometric, and photometric characteristics of the raw data transmitted by the spacecraft. This new volume set, on the other hand, contains cartographic compilations made by processing the raw images to reduce radiometric and geometric distortions and to form geodetically controlled Mosaicked Digital Image Models (MDIMs). (Because the photometric processing used in this MDIM was oversimplified, quantitative radiometric analysis on this data is not possible.) It also contains digitized versions of an airbrushed map of Mars as well as a listing of all IAU-approved feature names. In addition, special geodetic and photogrammetric processing has been performed to derive rasters of topographic data, or Digital Terrain Models (DTMs). The latter has a format similar to that of the MDIM, except that elevation values are used in the array instead of image brightness values. The Mars DTM exists in its entirety on Volume 7. Finally, Volume 7 has a listing of SPICE files derived for the Viking images used in the MDIM and the DTM. These files contain updated camera orientation matrices for each of the frames. The matrices are by-products of the photogrammetric processing for the control network required to compile the MDIM and the DTM. The CDROM collection serves two purposes. First, the MDIM and DTM collection serves as a data base for interactive map browser applications. Secondly, the CDROM volume set provides a dense delivery medium to build higher-derived cartographic image and topographic data products such as special map series and planning charts for the Mars Observer Project. This set contains seven volumes with the following contents: Volume 1 -------- Vastitas Borealis Region of Mars (VO_2001): MDIMs in 373 image files covering the entire north polar region of Mars southward from the pole to a latitude of 42.5 deg North. Polar Stereographic projection images of the north pole area from 80 to 90 degrees are located in the POLAR directory on this disk Volume 2 -------- Xanthe Terra Region of Mars (VO_2002): MDIMs in 412 image files covering the region of Mars from 47.5 deg North latitude to 47.5 deg South latitude, and 0 deg longitude to 90 deg West longitude. Volume 3 -------- Amazonis Planitia Region of Mars (VO_2003): MDIMs in 412 image files covering the region of Mars from 47.5 deg North latitude to 47.5 deg South latitude, and 90 deg West longitude to 180 deg West longitude. Volume 4 -------- Elysium Planitia Region of Mars (VO_2004): MDIMs in 412 image files covering the region of Mars from 47.5 deg North latitude to 47.5 deg South latitude, and 180 deg West longitude to 270 deg West longitude. Volume 5 -------- Arabia Terra Region of Mars (VO_2005): MDIMs in 412 image files covering the region of Mars from 47.5 deg North latitude to 47.5 deg South latitude, and 270 deg West longitude to 0 deg West longitude. Volume 6 -------- Planum Australe Region of Mars (VO_2006): MDIMs in 373 image files covering the entire South polar region of Mars northward from the pole to a latitude of 42.5 South latitude. Polar Stereographic projection images of the south pole area from 80 to 90 degrees are located in the POLAR directory on this disk Volume 7 -------- Digital Topographic Map of Mars (VO_2007): DTMs of the entire planet at 1/64, 1/16, and 1/4 deg/pixel; MDIMs of the entire planet at 1/64 and 1/16 deg/pixel; the digitized airbrush map of Mars at 1/16 and 1/4 deg/pixel; and revised SPICE files for all frames used to compile the MDIM and the DTM. Each of the first six volumes contains MDIMs of the areas specified at resolutions of 1/256 deg/pixel (231m) and at 1/64 deg/pixel (943m). Volumes 1, 6, and 7 also contain MDIM coverage of the entire planet at 1/16 deg/pixel (3.69 km). The seven volumes also include a digitized airbrush map of the entire planet at 1/16 deg/pixel (3.69 km) and at 1/4 deg/pixel. The Sinusoidal Equal-Area Projection is used for all MDIM and DTM files in this collection. Appendix E of this document contains a detailed description of the Sinusoidal projection and use of the cartographic keywords found in the image labels. The tiling layout of the 1/64 deg/pixel digital models is the same on the first six volumes, but has been modified on Volume 7. The Volume 7 1/64 deg/pixel tile scheme was modified so that each tile would contain approximately 1000 lines and 1000 samples. The 1/64 and 1/16 deg/pixel MDIM, segments of which appear in Volumes 1 through 6, is duplicated in its entirety on Volume 7. All of the resolution compressions were done by averaging, not by subsampling. A gazetteer of IAU-approved feature names, referenced by latitude/longitude coordinates is included as a table file on each of the seven volumes. Processing Level Id : 5 Software Flag : N Processing Start Time : 1990 Processing Stop Time : 1991 Parameters : Description ----------- Data Number is an integer expressing the digital value of an experiment's telemetry data. Sampling Parameter Name : PIXEL Data Set Parameter Name : DATA NUMBER Data Set Parameter Unit : DIMENSIONLESS Source Instrument Parameters : Instrument Host ID : VO1 Data Set Parameter Name : DATA NUMBER Instrument Parameter Name : RADIANCE Important Instrument Parameters : 1 Instrument Host ID : VO2 Data Set Parameter Name : DATA NUMBER Instrument Parameter Name : RADIANCE Important Instrument Parameters : 1 Processing : Processing History ------------------ Source Data Set ID : VO1/VO2-M-VIS-2-EDR-V2.0 Software : PICS Product Data Set ID : VO1/VO2-M-VIS-5-DIM-V1.0 Software 'PICS' --------------- The Planetary Image Cartography System (PICS) is an integrated computerized image processing and cartographic system for the systematic reduction, display, mapping, and analysis of planetary image data. A design goal in PICS was to develop a single set of generic software, simple to use, that would process any of the 150,000 planetary images from the Voyager, Viking, and Mariner Missions. This required standards to be developed so that formats for the image files, calibration files, geometric pointing and empherides files for all the missions, cameras, and targets be identical. Normally the PICS software modules are executed on images in groups called procedures. Provided in the PICS software set are the procedures that are used in the USGS Planetary Cartography effort. They are referred to as Levels 0 through 4. These five procedures are; Level 0 - data preparation, read raw planetary image from magnetic tape or CD-ROM to create a PICS image file, place geometry and camera instrument mode information in the image file labels for automatic processing; Level 1 - radiometric correction, bit-error suppression, reseaux processing, coherent noise suppression, and various cosmetic processes; Level 2 - geometric transformation including geometric distortion removal and projecting an image to a standard map projection and scale; Level 3 - image mosaicking, and Level 4 - photometric function processing (both characterizing the function as well as removing model functions.) The PICS manual describing more than 130 image processing programs can be obtained by contacting the Branch of Astrogeology, United States Geological Survey, 2255 North Gemini Drive, Flagstaff, AZ, 86001. Software Name : PICS Software Type : N/A Software Release Date : 1988-02-01 Node ID : RAD Cognizant Engineer : ERIC M. ELIASON Software Access Description : NOT ACCESSIBLE THROUGH PDS CATALOG - CONTACT NODE.
DATA_SET_RELEASE_DATE 1991-01-01T00:00:00.000Z
START_TIME 1972-07-01T12:00:00.000Z
STOP_TIME N/A (ongoing)
MISSION_NAME VIKING
MISSION_START_DATE 1975-08-20T12:00:00.000Z
MISSION_STOP_DATE 1983-02-01T12:00:00.000Z
TARGET_NAME MARS
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID VO1
VO2
INSTRUMENT_NAME VISUAL IMAGING SUBSYSTEM - CAMERA A
VISUAL IMAGING SUBSYSTEM - CAMERA B
INSTRUMENT_ID VISA
VISB
INSTRUMENT_TYPE CAMERA
NODE_NAME Imaging
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : COMPILATION OF DIMs ------------------- Digital image models are compiled and archived in four stages or 'levels', beginning with raw images. All of the corrections made during these stages have some level of uncertainty, so the processing sequence is designed to progress from corrections with the highest probability of accuracy to the lowest, and intermediate stages are preserved for future analytical use. Image processing software exists to perform the various stages of image correction and enhancement [PETTENGILLETAL1980C; SODERBLOM1978]. LEVEL 1: RADIOMETRIC CORRECTION ------------------------------- Level 1 processing includes removal of electronic shading, which is inherent in the imaging system, and artifacts such as minute dust specks on the vidicon tube, microphonic noise introduced by operation of other instruments on the spacecraft during imaging sequences, and data drop-outs and spikes [WU&DOYLE1990]. Reseau marks are also located and removed during this stage; their precise locations are recorded for use during later geometric processing. A digital image label is created, containing the reseau-mark locations, geodetic control point and image tie-point locations, and a computed camera orientation matrix that will project the frame to a best-fit shape and position in a mosaic. Level 1 images have better resolution than those produced at any subsequent processing level. This is because they have not been resampled for geometric correction and projection; some loss of information is inevitable in any resampling, because the density values of multiple pixels and/or fractional pixels must be averaged to form new pixels in the output array. Photographic copies of Level 1 images, with spatial filter enhancement, are therefore the more useful photographic materials for visual interpretation. Plans for publication and distribution of Level 1 images on CDROM have been cancelled, however, because the processing has become so efficient that it is less expensive to reprocess images on demand than to archive previous processing. The control information and projection matrices contained in Level 1 image labels are preserved as text files, and can be easily recovered if reprocessing is needed. LEVEL 2: GEOMETRIC CORRECTION ----------------------------- Level 2 processing includes removal of camera distortions and transformation from image to map coordinates in DM format according to parameters derived at the end of the Level 1 processing phase [BATSON1990A]. The resolution of each frame is preserved to some extent by oversampling in the output array; that is, by selecting a resolution step that results in an image with more lines and samples than the original image. Distortion corrections are based on preflight calibration of the reseau. Image transformation is based on camera orientation matrices derived by photogrammetric triangulation [25] modified as required for a best fit with adjacent images. On those images where matrices are not available, they are derived by matching corresponding points with images that have matrices. LEVEL 3: PHOTOMETRIC CORRECTION ------------------------------- At level 3 processing apparent inconsistencies in surface brightness caused by variation in illumination geometry and by atmospheric effects are treated. Atmospheric scattering is a significant consideration on Mars. Different materials on any planet have different light-reflecting properties. Other photometric corrections are effective only to the extent that all geometric parameters can be modeled. In general, local topography is not included in the model (i.e., the surface model used is flat). Illumination geometry at each pixel, however, certainly depends on local topography; unless the topographic slope within a pixel is accurately known and compensated, the photometric correction cannot be perfect. All of these conditions are so complex that photometric correction of planetary images is likely to be only approximate for some time into the foreseeable future, although research into the effects and prototype examples of full three-dimensional treatment are now being pursued. An obvious example of the complexity of the problem would consist of a pair of images of the same landform illuminated from opposite directions. Only an extremely complex algorithm could accurately modify the shading in one of the images to match that of the other. No algorithm could restore detail lost in shadow. The photometric processing used in this MDIM was necessarily oversimplified, and incorporates spatial filtration that has the effect of subduing regional albedo markings. LEVEL 4: CONTROLLED MOSAICKING ------------------------------ Compilation of an accurate digital mosaic (MDIM) of the entire surface of a planet is the final stage in the construction of a DIM. The MDIM is a digital image of the planet, with uniform resolution throughout. The resolution of level 2 images used in the compilation is compressed or expanded to match that of the MDIM.
CITATION_DESCRIPTION Citation TBD
ABSTRACT_TEXT This digital image map of Mars is a cartographic extension of a previously released set of CDROM volumes containing individual Viking Orbiter Images (PDS volumes VO_1001, VO_1002, etc.). The data in the latter are pristine, in the sense that they were processed only to the extent required to view them as images. They contain the artifacts and the radiometric, geometric, and photometric characteristics of the raw data transmitted by the spacecraft. This new volume set, on the other hand, contains cartographic compilations made by processing the raw images to reduce radiometric and geometric distortions and to form geodetically controlled Mosaicked Digital Image Models (MDIMs). (Because the photometric processing used in this MDIM was oversimplified, quantitative radiometric analysis on this data is not possible.) It also contains digitized versions of an airbrushed map of Mars as well as a listing of all IAU-approved feature names. In addition, special geodetic and photogrammetric processing has been performed to derive rasters of topographic data, or Digital Terrain Models (DTMs). The latter has a format similar to that of the MDIM, except that elevation values are used in the array instead of image brightness values. The Mars DTM exists in its entirety on Volume 7. Finally, Volume 7 has a listing of SPICE files derived for the Viking images used in the MDIM and the DTM. These files contain updated camera orientation matrices for each of the frames. The matrices are by-products of the photogrammetric processing for the control network required to compile the MDIM and the DTM.
PRODUCER_FULL_NAME ERIC ELIASON
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