DESCRIPTION OF THE DIGITAL DATABASE FOR 
Geologic Map of the Snegurochka Planitia Quadrangle (V-1), Venus
U.S. GEOLOGICAL SURVEY SCIENTIFIC INVESTIGATIONS MAP 3178

INTRODUCTION

This digital database for the Geologic Map of the Snegurochka 
Planitia Quadrangle (V-1), Venus 
(http://pubs.usgs.gov/sim/3178/) includes several GIS 
features that collectively present the entire content of 
the geologic map, along with supporting files and metadata.  
Data is in ArcGIS geodatabase format and is collated within
a single feature dataset  that preserves the relevant
geographic information.  Together with the geologic pamphlet,
the GIS database  provides georeferenced information on the
geologic units, structure, and morphology of the V-1 quadrangle.  

All GIS data are in Polar Stereographic projection 
using the Venus 1985 geographic coordinate system 
(GCS_Venus_1985).  Units are in meters.

Citation:  Hurwitz, D.M., and Head, J.W., 2012, Geologic map 
of the Snegurochka Planitia quadrangle (V-1), Venus: U.S. Geological
Survey Scientific Investigations Map 3178, pamphlet 28 p., 1 sheet,
scale 1:5,000,000. (Available at http://pubs.usgs.gov/sim/3178/ )

GEOLOGIC CONTENT

This database contains one ArcGIS feature dataset with the 
following geologic content:

GeoContacts - Final geologic contact polyline feature 
class. Contains a "TYPE" field denoting the type of 
geologic contact.

GeoUnits - Final geologic unit polygon feature class.  
Contains a "Shape_Area" field containing the area of each 
polygon, as calculated using the map projection. Contains a 
"UnitName" field denoting the unit name.  Contains a "Unit" 
field denoting the unit symbol.

LinearFeatures - Final structural and morphologic polyline 
feature class.  Contains a "TYPE" field denoting the type 
of linear feature.

LocationFeatures - Final locational feature point feature 
class.  Contains a "TYPE" field denoting the type of 
locational feature.

MapBoundary - Quadrangle boundary as polygon feature class.

BASE MAP CONTENT

Image mosaics of Magellan radar backscatter served as the 
primary data set used to delineate boundaries of discrete 
geologic units and to characterize their appearance, 
morphology, and distribution.  Basemap was provided by USGS 
Astrogeology Science Center as an 8-bit raster image 
representing radar backscatter in Polar Stereographic 
projection using the Venus 1985 geographic coordinate 
system.  Topographic data provided supplemental 
information in the identification and description of 
geologic units and features.  These data are available for 
download at: 

     http://www.mapaplanet.org/

DIGITAL DATABASE AND METADATA PACKAGE 
(SIM3178_Data.zip)

The geologic map files, basemap, and supportive files are 
included in the database package, as described below:

File               Description
-----------------------------------------------------------

SIM3178_readme.txt           This readme file.

SIM3178_metadata.txt         Text-format FGDC-style 
                              metadata for the database 
                              package

SIM3178_metadata.xml          XML-format FGDC-style 
                              metadata for the database 
                              package

V1_SIM3178_ArcMap93_5M.mxd    ArcGIS 9.3 and 10 projects provided
                              for the database package. Also a 
                              ArcReader project is also provided.


V1_SIM3178_GeoDatabase.gdb    ArcGIS geodatabase containing 
                              all digital geologic map 
                              information

"Shapefiles" directory
--------------------------------------------

Contains the geologic digital layers in a alternative GIS format for
use across many GIS applications.


"Layer_Definitions" directory
--------------------------------------------

GeoContacts.lyr               ArcGIS layer file containing 
                              contact symbol look-up table

GeoUnits.lyr                  ArcGIS layer file containing 
                              unit color look-up table

LinearFeatures.lyr            ArcGIS layer file containing 
                              line feature symbol look-up 
                              table

LocationFeatures.lyr          ArcGIS layer file containing 
                              location feature symbol look-
                              up table

Channels.lyr                  ArcGIS layer file containing 
                              channel feature symbol look-
                              up table


"Raster_Basemaps" subdirectory
--------------------------------------------

v1_base.tif                   TIFF-format 
                              Magellan radar mosaic

gdtrnorthtopo-r.tif           TIFF-format of the Magellan
                              GETR elevation

*.tfw                         World files that locates 
                              both Magellan radar images


Users of the database package may wish to download the 
technical and/or nontechnical pamphlet 
(http://pubs.usgs.gov/sim/3178/) for the contained 
Description of Map Units.

The material described above is available on the World Wide 
Web at http://pubs.usgs.gov/sim/3178/.

ZIP FILES

The files described above are packaged within a ZIP file.  
Utilities to uncompress ZIP files are available for most 
operating systems and may be found readily with a simple 
web search.

DIGITAL DATABASE FORMAT

The digital information compiled in this report used ArcGIS 
v 9.3, a commercial Geographic Information System produced 
by Environmental Systems Research Institute, Redlands, 
California.

OBTAINING HARD-COPY OF SIM-3178

USGS Information Services
Box 25286
Federal Center
Denver, CO  80225-0046

1-888-ASK-USGS (1-888-275-8747)
Email: infoservices@usgs.gov
World Wide Web- http://www.usgs.gov/pubprob

For additional information, please contact:
Astrogeology Science Center
U.S. Geological Survey
2255 N. Gemini Drive
Flagstaff, AZ  86001
http://astrogeology.usgs.gov