color map above is a screen capture of a state-wide composite
of the all of the 1133 GAT Quads in an ArcView 3.x view
using an auto-loading Avenue script, representing 1.6
GB of raster data. Printing the map on a wide-bed, color
plotter will reveal more detail than the image shown here.
It was generated on a 3.05 GHz GIS PC with 1GB of RAM.
The ability to load all of the Digital GAT Quads (and
print them) is dependent upon the computer processing
speed and available RAM (the faster with more RAM, the
Quad and legend files are divided geographically into
SE, NE, NW, and SW quadrants of the state (approximately
2.05 GB total)
dataset, designed for use with ArcView GIS 3.x and 8.x
software products, consists of 1133 georeferenced 15-minute
GAT (Geologic Atlas of Texas) quadrangle tiff images
along with 1357 scanned legend and formation description
images. The world file extension has been changed to
"tfw" (from "tifw") for compatibility
with other GIS software products that are sensitive
to the "tifw" file extension (e.g., Map Info).
Layer files (used in ArcView 8.x) for the 1-degree quads
have been included to display up to 16 GAT Sheets at
a time as a seamless image. Pyramid image files are
included for faster frame redraw in ArcView 8.x.
John D. Estepp, P.G. TCEQ Surface Casing
handling and sales tax if shipped to a Texas address.