Types of data
 |
 |
| Raster |
Raster with Vector Overlay |
There are two types of data
included on this Web site: raster
and vector. The raster (or pixel-based) data includes all
of the satellite imagery as well as the derived products, including
composites, vegetation index, and unsupervised classification. The vector (or point-line-polygon) data includes several datasets
that provide the user with a context in which to view the raster data.For example, roads (vector) can be displayed
over a satellite image to help the viewer more easily locate known
features.Streams and watersheds (also vector) can also
be drawn over these data sets to provide further reference.
File
formats
Raster
data is provided in GeoTIF format (.TIF) and can be read by most software
packages that display images (image processing, GIS, and standard
photo/image editing packages). As
a result, virtually anyone with a computer can display the satellite
imagery and derived products made available on this site.
Vector data is provided in shapefile format
(.SHP).
Since there is no easily usable standard for this type of data, the
shapefile format, which was designed by Environmental Systems Research
Institute (ESRI), was chosen because of its widespread use within
the GIS community. Many software packages can import this file
type, and free viewers such as ArcExplorer are available
and easy to use. IMPORTANT
NOTE: A single “shapefile” consists of three separate files (.SHP,
.SHX, .DBF). Make sure that all three files are present and
in the same folder when data is imported, otherwise the data will
not be usable.
Both
raster and vector files have been compressed to a .ZIP file. After the data has been downloaded, it must be uncompressed
using WinZip or a similar package
before it can be used.
File
naming conventions
A
standard naming convention was established for all data made available
through this Web site.
Convention:????_XXXX_ZZ_YYMMDD.FFF
| |
|
| ???? |
represents data content
theme (see table below) |
| XXXX |
represents county name |
| ZZ |
represents state name |
| YYMMDD |
represents date of imagery (for
raster data only) |
| FFF |
represents file format (.tif for raster and .shp for vector) |
