Geographic Information Systems Projection File Directory

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Data Page | Projections | Three-Letter Codes | Map

The projection_file directory contains projection definition and projection conversion files for projections commonly used by the California BLM.  These files can be used to define the projections of ArcInfo coverages and grids, or to reproject ArcInfo coverages and grids.

Both the projection definition and projection conversion files have a ?. prj' extension.

The projection file names include an abbreviated version of the projection name, a zone reference or an indication of the spatial area on which the projection is centered, and a datum. 

Projection names in this directory include:

albca	A California-centered Albers projection, also referred to as 'Teale Albers'
albus	A United States-centered Albers projection
ctm	A California-centered transverse Mercator projection
geo	Non-projected data stored in geographic coordinates (longitude, latitude)
sp	State planes coordinate system.  The zone references for the state plane coordinate system are the 4-digit USGS State plane zones.  See ESRI's  ?State Plane Coordinate System Tables' for this reference.
utm	Universal transverse Mercator coordinate system.  Zones represented in this directory include 10, 11, and 12.

                                                              

The datums include NAD27 and NAD83.

The naming convention for the projection conversion files is:  <inprojection><outprojection>.prj

For example, albca27utm1183.prj projects from the California-centered Albers NAD27 projection to UTM Zone 11, NAD83.