About the Data
Datasets available for download through the Wyoming BLM clearinghouse may be available in two formats: Arc/Info export format or ArcView shapefile format or both. Arc/Info is the proprietary GIS software that this data was developed in, and is available from ESRI. Both export files and shapefiles can be brought into ARC/INFO, ArcView, and several other GIS software systems. Shapefile format can also brought into ArcExplorer, ESRI's free data explorer.
Because some statewide datasets may be extremely large and slow to process, they are also provided in smaller-areas tiles, either by counties (23 in Wyoming), by 30 by 60 minute quadrangle (56 in Wyoming), or by 7.5 minute quadrangles.
Most of datasets are in latitude/longitude (decimal degrees), North American Datum 1983, unless otherwise noted. Check the Spatial Reference Information section of the dataset's metadata document to find out its projection and datum information.
Most GIS software packages can easily convert decimal degrees into other projections. In ArcView, data in decimal degrees can be projected "on the fly" simply by selecting the desired projection from off a menu. The ArcView Projector extension can also be used to perform permanent projection changes, which is necessary in order to overlay datasets in different projections.
Steps for Downloading the Data
- To download the file, you must press the shift key as you click on the file name, otherwise your browser may attempt to view the data. The metadata document can be downloaded separate from the data, however it is also included in the zip file. Metadata files have the extension *.met and are plain text files that can be viewed in any text editor or word processor.
- The data files are stored as zipped export or shape files. The compression software is INFOZIP (Zip 2.1) which is compatible on both UNIX and PC platforms as well as compatible with pkzip software.
- Infozip can be downloaded at http://www.cdrom.com/pub/infozip.
- Pkzip can be downloaded at http://www.pkware.com/shareware.
Steps for Importing the Data
Export files: once unzipped, the export file (identified by an .e00 extension) can be imported to Arc/Info coverages by the Arc/Info import command:
For vector coverages: import cover
For raster grids: import grid
Typically, after importing the file into Arc/Info or Arcview, the actual coverage or grid will be smaller in size than the export file.
Any associated INFO files will also automatically be imported into the same directory as the coverage. Associated INFO tables usually contain descriptions of attribute codes. More information about the dataset's attributes can be found in the Entity/Attribute section of the dataset's metadata document.
- Shapefiles: Shapefiles can be converted to ARC/INFO format by the shapearc command. (Note: a shapefile actually consists of three files, with a *.shp, *.shx, and *.dbf extension). Additional tables in dBase (.dbf) format must be converted to INFO before they can be used in Unix or NT ARC/INFO. Use the dbaseinfo command to convert the format.
- Shapefiles: once unzipped, shapefiles can be brought directly into ArcView by adding a theme. (Note: a shapefile actually consists of three files, with *.shp, *.shx and *.dbf extension).
Additional Dbase tables (*.dbf) can be brought into ArcView by adding a table.
- Export files: once unzipped, the export file (identified by an .e00 extension) can be imported with the ArcView system executable import (ArcView 2.1) or import71 (ArcView 3.0).
Associated files in INFO format can be brought into ArcView by "adding a table" from the Project Manager. You will need to change the file type from the default, .dbf, to INFO and change directories to the info directory.
Associated .dbf or INFO tables usually contain descriptions of attribute codes. More information about the dataset's attributes can be found in the Entity/Attribute section of the dataset's metadata document.
In some cases, an ARC/INFO coverage may have both polygon and line topology. In these cases, the dataset must be added as a theme twice, once as a arc (line) theme and once as a polygon theme. In the Add Theme dialog box, click once on the folder representing the data you want to add. By clicking on it once, it will display which features are available to add: polygon, arc or labelpoint. Then double click on which feature you would like to add.