GIS Downloadable Data

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Data Page | Projections | Three-Letter Codes | Map

Downloadable data is now available at http://www.blm.gov/ca/gis/index.html

BLM Data Naming Rules

The Three-letter theme codes are part of the standard coverage naming convention used in California.  This naming convention was established to help facilitate the limited coverage name length in arc/info (max 13 characters) and establish some type of standards to identifying the contents of our single-theme-based coverages.

The naming convention is as follows:

xxxyzzzzzz11
where

xxx = The three-letter theme code

y = what type of data in the theme/coverage

The data type contained in this coverage.  Valid data types are:

p -polygon/area data                                                                                 

l - line/linear data

m - marker/point data 

g - grid/lattice data

t - tin data

a - annotation data

zzzzzz = where the data is 

The geographic extent of data.  Geographic extent can be represented by the state (ca), field office name/code (cdd, 060), optional code designated by the Field Office, or one of the standard California map naming convention codes used to identify a quad location and scale.  Generally this code would include a two digit latitude, a three digit longitude (drop the "_" sign), and at the end, the two character code from the USGS "Ohio Convention"

11 = optional characters used to further identify the coverage

Examples:

hydpca	hydrography, polygon data for california. data such as lakes
hydm39123b2	hydrography, marker (point) data for the 7.5  minute quad, Ukiah data such as springs.
hydlcdd	hydrography, line data for the California Desert District data such as rivers and streams.