Comma Separated Values. An ASCII text file where each the data for each attribute (column) of a row is separated from adjoining columns by commas. The columns that contain text will have double quotes (") enclosing their values. The first row in this file contains the names of the columns.

Microsoft Excel and many other programs can read CSV files. However, this file can not be displayed as a map directly by a GIS. First, it must be joined to spatial data.

ESRI Shapefile theme: a file format made popular by ESRI ArcView. A shapefile theme is composed of at least three files: .shp, .shx, and .dbf. These three files hold geometry data and attribute information. Also, a .prj file can be present to document projection. The SF3 downloader will add a .csf file to document projection for Intergraph Geomedia.

A number of different programs can read shapefile themes. Since these files contain geometry data, GIS and mapping applications can display the data in a map context. Most GIS and mapping applications can easily make thematic or chloropleth maps from the downloaded shapefile theme.

When a user selects SHP as the file format to use for downloading, the Atlas Census2000 SF3 downloader will join the SF3 table records of the geography summary level to a digital map of the same geography by the FIPS column and then will convert the joined records from a database format into a ESRI shapefile theme.

The source for the digital maps the downloader uses for is the US Census Bureau (with the exception of the parish map). These maps can be found at http://www.census.gov/geo/www/cob/index.html. The parish map is a digital map the LSU CADGIS Lab created by digitizing parish boundaries from 1:250,000 scale USGS topographic sheets. Atlas uses this map because it shows parish land boundaries and not legal boundaries that extend over water. The parish map was digitized from 1:250,000 scale maps and therefore, SHOULD NOT BE USED at larger scales.

The coordinate system for the shapefiles created by the Census2000 SF3 downloader is geographic in decimal degrees. The datum is North American Datum 1983.