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.
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
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