Geologic Map of Part of Western Hellas Planitia, Mars
May 15, 2018

The original geologic map was created in 2007 from Viking Orbiter imagery. To make this map more useful with modern data it has been georeferenced to align with the more modern 2014 THEMIS Daytime IR imagery. Links used to transform the data are included with this documentation. A polyline feature class was created to digitize contacts at 1:200k, and attributed with contact type. A polygon feature class was created from this polyline feature class, attributed with geologic unit labels, and symbolized based on RGB values identified from the map sheet TIFF in Adobe Photoshop.

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Data are saved in a feature dataset in SIM2953_PartOfWesternHellasPlanitia_1M.gdb

SIM2953_PartOfWesternHellasPlanitia_1M.gdb_GeoContacts (polyline feature class)
SIM2953_PartOfWesternHellasPlanitia_1M.gdb_GeoUnits (polygon feature class)

GCS_Mars_2000_Sphere
Projection    	Transverse_Mercator

Zunits        NO                                                                
Units         METERS                                                            
Xshift        0.0000000000                                                      
Yshift        0.0000000000                                                      
Parameters 3396190.0000000000  3396190.0000000000                               
60.00000 /* longitude of central meridian                                   
0.000 /* latitude of true scale                                          
0.00000 /* false easting (meters)                                       
0.00000 /* false northing (meters)

Separate shapefiles of the two feature classes are located in the ...Data/Shapefiles/ directory.

The coordinate system used for this digitization is based on the coordinate system stated on the map sheet and is stored in ...Documentation/CoordinateSystems/ directory.

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

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Below are the RGB values sampled from the scanned map sheet used to symbolize geologic units and saved as a layer (*.lyr) file in the ...Data/LayerFiles/ directory. 

GeoUnit		      RGB
As        255 234 217
AHs       187 227 224
AHh       136 208 199
Hp        187 192 210
Hw        139 178 208
Hk        155 162 209
Hr        228 206 228
Hsr       227 221 122
Hpl3      200 234 251
Hpl2      167 198 233
Hpl1      31  196 244
HNp       189 169 189
Npl       230 192 177
Nb        228 167 174
AHc       255 245 121
Hc        176 217 164
Nc        207 158 107
           
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For more information, contact:
Michelle Barton
mbarton@usgs.gov
USGS Astrogeology Science Center
Flagstaff, AZ
(928)556-7177