1:5M Digitization of the Geologic Map of the Elysium Region of Mars
July 18, 2016

The original map document was created in 1992 as a Mercator projection and is based on older Viking images. It was scanned and georeferenced into ArcGIS in two parts that are located in Elysium_5M_Viking/Raster/Elysium_clip3_RECTIFY and Elysium_clip4_RECTIFY. An uncontrolled THEMIS 100 mpp basemap and a MOLA hillshade were used for georeferencing. Control point links can be found in Elysium_5M_I2147_Viking/Raster/Elysium_I2147_clip3_links and Elysium_I2147_clip4_links. The geologic structures mapped on the original map document were not digitized or converted into GIS.

Original map contacts (approximate and certain) were digitized with a streaming tolerance of 1500 meters at a 1:750000 scale. The polylines were then converted into polygons which were attributed with the same geologic symbols and colors as shown on the original scanned map. There were no revisions made to the preexsiting geologic contacts in order to preserve the original documentation of the units. 

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References:
Kenneth L. Tanaka, Mary G. Chapman, and David H. Scott, 1992, Geologic map of the Elysium region of Mars: U.S. Geological Survey Investigations Series I2147, scale 1:5000000, https://pubs.er.usgs.gov/publication/i2147
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GeoUnits (polygon feature class)
GeoContacts (polyline feature class)
Saved in a feature dataset in Elysium_5M_I2147_Viking/Data/Elysium_I2147_geodatabase.gdb/ElysiumGeology

Projection    Mercator                                                          
Zunits        NO                                                                
Units         METERS                                                            
Xshift        0.0000000000                                                      
Yshift        0.0000000000                                                      
Parameters 3396190.0000000000  3396190.0000000000                               
 0  0  0.000 /* longitude of central meridian                                   
 0  0  0.000 /* latitude of true scale                                          
0.00000 /* false easting (meters)                                       
0.00000 /* false northing (meters)           

Coordinate systems used for this quadrangle are stored in Elysium_5M_I2147_Viking/Data/Coordinate_system

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Basemaps have not been included in this download package, but the most current bases using THEMIS and MOLA data are available through ArcGIS Online or can be downloaded at the following link:
http://astrogeology.usgs.gov/search/map/Mars/Odyssey/THEMIS-IR-Mosaic-ASU/Mars_MO_THEMIS-IR-Day_mosaic_global_100m_v12

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For more information contact:
Michelle Barton
mbarton@usgs.gov
USGS Astrogeology Science Center
Flagstaff, AZ

James A. Skinner Jr.
jskinner@usgs.gov
USGS Astrogeology Science Center
Flagstaff, AZ