Viking VISAB Mosaicked Digital Image Models (MDIM)
MDIM – Mosaicked Digital Image Models
Instrument:Visual Imaging Subsystem Cameras A and B
DOI: 10.17189/1520376.
For more information about VISAB MDIM products, see the Data Set Catalog File.
The Visual Imaging Subsystem Cameras A and B (VISAB) Mosaicked Digital Image Models (MDIMs) are a cartographic extension of the Experiment Data Records (EDRs). They contain cartographic compilations made by processing the raw images to reduce radiometric and geometric distortions to form geodetically controlled images.
Note: The west positive aerographic coordinates in the label of Viking Orbiter VISAB MDIM data products have been converted to east positive aerocentric coordinates in the ODE metadata database.
There are 7 volumes of MDIMs. Volumes 1-6 have been redelivered in a second version (2.0) that has been improved in both geodetic accuracy and photometric/cosmetic appearance. The most significant change is geodetic: the present mosaic is based on a 1999 RAN global geodetic control network of Mars. This net is tied to the inertial-space position of the Mars Pathfinder spacecraft and incorporates elevation data from the Mars Orbiter Laser Altimeter (MOLA) for most control points. Its use thus eliminates a systematic error in longitude in the previous mosaic and reduces random positional errors that in some locations exceeded 20 km to typically less than 1 km. Details about these redelivered products can be found here.
In addition, the USGS has released a version 2.1 MDIM map that increases the positional accuracy of the map even more than version 2.0, as well as making more photometric and cosmetic improvements. Those map products can be found here. The 2.1 MDIM can be chosen as an ODE Basemap for displaying Mars data products.
Each of the first six volumes contains MDIMs of the areas specified at resolutions of 1/256 deg/pixel (231 m) and at 1/64 deg/pixel (943 m). Volumes 1 and 6 also contain MDIM coverage of the entire planet at 1/16 deg/pixel (3.69 km). The six 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 1/64 deg/pixel MDIM segments which appear in volumes 1-6 are duplicated in its entirety in volume 7.
The contents of the 7 volumes are below (with links to the volume).
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Volume |
Contents |
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Vastitas Borealis Region of Mars: MDIMs in 373 image files covering the entire north polar region of Mars southward from the pole to a latitude of 42.5 degree north. Polar Stereographic projection images of the north pole area from 80 to 90 degrees are located in the EXTRAS/POLAR directory on this disk. |
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Xanthe Terra Region of Mars: MDIMs in 412 image files covering the region of Mars from 47.5 degree north latitude to 47.5 degree south latitude, and 0 degree longitude to 90 degree west longitude. |
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Amazonis Planitia Region of Mars: MDIMs in 412 image files covering the region of Mars from 47.5 degree north latitude to 47.5 degree south latitude, and 90 degree west longitude to 180 degree west longitude. |
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Elysium Planitia Region of Mars: MDIMs in 412 image files covering the region of Mars from 47.5 degree north latitude to 47.5 degree south latitude, and 180 degree west longitude to 270 degree west longitude. |
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Arabia Terra Region of Mars: MDIMs in 412 image files covering the region of Mars from 47.5 degree north latitude to 47.5 degree south latitude, and 270 degree west longitude to 0 degree west longitude. |
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Planum Australe Region of Mars: 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 EXTRAS/POLAR directory on this disk. |
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Digital Topographic Map of Mars: 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. |
VISAB MDIM products have the following file names:
twaadooo.img
where:
t = type of image file
M = Mars Digital Image Map
T = Mars Digital Topographic Model
S = Shaded Relief Airbrush Map
w = Resolution code for image file (in degree/pixel)
C = 1/4
E = 1/16
G = 1/64
I = 1/256
aa = Central latitude value rounded down to nearest whole latitude
d = latitude direction
N = North latitude
S = South latitude
ooo = Central longitude value rounded down to nearest whole longitude
In ODE, MDIM products have the following Product IDs:
TWAADOOO.IMG