California and Nevada - Description

Overview

Shuttle Radar Topography Mission
U. S. Census Bureau Tiger Map Server

Elevation Data

This site provides SRTM elevation files, "finished" grade, ready to be used with Truflite for Windows, as digital elevation model (DEM) files.

The elevation files were corrected at Martin D. Adamiker's for void (zero altitude) areas. The correction method will be explained in more detail later this year.

Example:

33N115W_el.tga.bz2: This is a regular TGA file that can be used with TruFlite for Windows. It was compressed using the bzip2 utility. This compression tool has shown to yield fairly small files. The tool is available from http://www.bzip.org, also in a Windows version. GIMP, the GNU Image Manipulation Program (http://www.gimp.org), can directly read such files.

33N115W_el.png: PNG is another image format with excellent compression rates and a large variety of applications, of course including GIMP. Standard web browsers have been able to display such files directly for quite a while, just like GIF and JPEG. Future TruFlite versions will support the PNG format.

Texture Data

Also, texture files from the U. S. Census Bureau Tiger Mapping Server are available. The Tiger texture files were further also colored to reflect the altitude. Each texture file maps exactly over its elevation counterpart.

The horizontal DEM resolution is one arc second (approx. 30 meters), the vertical resolution is 1 meter.

Example:

33N115W_tx_c.tga.bz2: Again, this is a regular TGA file that can be used with TruFlite for Windows, compressed using the bzip2 utility.

33N115W_tx_c.png: A texture file in PNG format. Future TruFlite versions will support the PNG format.

Projection

The elevation files are all 3600 by 3600 pixels, which means one arc degree by one arc degree, as their horizontal resolution is one arc second.

In theory, one could tile one degree quads to form an area much larger than one square degree.

The texture files were adapted to support tiling: all texture files were scaled to a unique width of 4044 pixels, regardless the latitude.

The Clickable Image Maps

From the Overview map, locate the one degree quadrangle you are interested in. Each quadrangle links to a page listing the files.

This is the legend for the one degree maps:

map legend

This site's predecessor, the map of the USGS 7.5 Minute Digital Elevation Files of California, was archived ine June 2009: cadems.zip (11 MB).


This page was last updated: 02/13/13.
Copyright 1996-2013 Martin D. Adamiker's. All Rights Reserved.