State of Texas -- Highlighting Low-Lying Areas Derived from USGS Digital Elevation Data By John J. Kosovich 2008 U.S. Geological Survey Scientific Investigations Map 3050 I. SUMMARY: In support of U.S. Geological Survey (USGS) disaster preparedness efforts, this map depicts a color shaded relief representation of Texas and a grayscale relief of the surrounding areas. The first 30 feet of relief above mean sea level are displayed as brightly colored 5-foot elevation bands, which highlight low-elevation areas at a coarse spatial resolution. Standard USGS National Elevation Dataset (NED) 1 arc-second (nominally 30-meter) digital elevation model (DEM) data are the basis for the map, which is designed to be used at a broad scale and for informational purposes only. The NED data were derived from the original 1:24,000-scale USGS topographic map bare-earth contours, which were converted into gridded quadrangle-based DEM tiles at a constant post spacing (grid cell size) of either 30 meters (data before the mid-1990s) or 10 meters (mid-1990s and later data). These individual-quadrangle DEMs were then converted to spherical coordinates (latitude/longitude decimal degrees) and edge-matched to ensure seamlessness. The NED source data for this map consists of a mixture of 30-meter- and 10-meter-resolution DEMs. State and county boundary, hydrography, city, and road layers were modified from USGS National Atlas data downloaded in 2003. The NED data were downloaded in 2002. Shaded relief over Mexico was obtained from the USGS National Atlas. II. DISCLAIMERS: These data are designed to support U.S. Geological Survey (USGS) disaster preparedness efforts and is meant to be used at a broad scale and for informational purposes only. This database, identified as SIM 3050, has been approved for release and publication by the Director of the USGS. Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the United States Government may be held liable for any damages resulting from its authorized or unauthorized use. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty, expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and/or contained herein. Although this information product, for the most part, is in the public domain, it also contains copyrighted materials as noted in the text. Permission to reproduce copyrighted items for other than personal use must be secured from the copyright owner. Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. III. CONTENTS SIM3050.pdf README.txt DataFiles: tx_ned150 tx_ned150_b tx_ned150_g tx_ned150_r info stk_tx SIM3050_elevation_TX.pdf metadata metadata_stk_tx.txt metadata_tx_ned150.txt metadata_tx_ned150_b.txt metadata_tx_ned150_g.txt metadata_tx_ned150_r.txt IV. DATA FILE DESCRIPTIONS: tx_ned150 = Elevation grid of Texas derived from 30-meter (1 arc-second) National Elevation Dataset (NED) data which was then resampled down to 150 meters. These data are designed to support U.S. Geological Survey (USGS) disaster preparedness efforts and are meant to be used at a broad scale and for informational purposes only. tx_ned150_b = Blue channel grid of Texas derived from 30-meter National Elevation Dataset (NED) data which was resampled down to 150 meters. When combined with the corresponding red and green grids into a multi-band dataset or grid stack, these datasets depict a color shaded relief representation of the state, in which the first 30 feet of relief above mean sea level are displayed as brightly colored 5-foot elevation bands (refer to legend file "SIM3050_elevation_TX.pdf"). These data are designed to support U.S. Geological Survey (USGS) disaster preparedness efforts and are meant to be used at a broad scale and for informational purposes only. tx_ned150_g = Green channel grid of Texas derived from 30-meter National Elevation Dataset (NED) data which was resampled down to 150 meters. When combined with the corresponding red and blue grids into a multi-band dataset or grid stack, these datasets depict a color shaded relief representation of the state, in which the first 30 feet of relief above mean sea level are displayed as brightly colored 5-foot elevation bands (refer to legend file "SIM3050_elevation_TX.pdf"). These data are designed to support U.S. Geological Survey (USGS) disaster preparedness efforts and are meant to be used at a broad scale and for informational purposes only. tx_ned150_r = Red channel grid of Texas derived from 30-meter National Elevation Dataset (NED) data which was resampled down to 150 meters. When combined with the corresponding green and blue grids into a multi-band dataset or grid stack, these datasets depict a color shaded relief representation of the state, in which the first 30 feet of relief above mean sea level are displayed as brightly colored 5-foot elevation bands (refer to legend file "SIM3050_elevation_TX.pdf"). These data are designed to support U.S. Geological Survey (USGS) disaster preparedness efforts and are meant to be used at a broad scale and for informational purposes only. info = database folder containing proprietary grid files and pointers stk_tx = R,G,B grid stack of the three "tx_ned150_"r,g,b grids (can be viewed as a three-band raster in ArcMap) SIM3050_elevation_TX.pdf = Explanation of elevation color ranges used for the Texas dataset V. SYSTEM REQUIREMENTS: PDF files may be viewed using any hardware platform that supports standard Adobe products. Elevation and color grids may be viewed using hardware that supports ESRI's ArcGIS or other compatible GIS software. Minimum System Requirements Windows-based computer: Intel Pentium processor computer (486 minimum, Pentium or Pentium Pro preferred),with Microsoft Windows XP, Windows 2000, or Windows NT 4.0 with Service Pack 5 or later 512 MB of RAM minimum Macintosh computer: Power PC G3, G4, G5 processor Mac OS X v. 10.2.8 or higher 512 MB of RAM minimum ArcGIS 9.1 on PC-Intel is preferred, older versions may also work CPU speed: 1.0 GHz or higher Processor: Intel Pentium or Intel Xeon Processors Memory/RAM: 512 MB minimum, 1 GB or higher Screen resolution: 1024 x 768 or higher Display properties: Greater than 256 color depth Swap space: Determined by the operating system, 500 MB minimum Disk space: 1 GB or higher VI. INSTRUCTIONS AND DOCUMENTATION FOR U.S. GEOLOGICAL SURVEY SCIENTIFIC INVESTIGATIONS MAP 3050 To access the data: The data files can be downloaded via the web from http://pubs.usgs.gov/sim/3050 The main product is a Portable Document Format (.pdf) map, which requires Adobe Acrobat for viewing. Acrobat software runs on a variety of systems, and is available for download free of charge from Adobe at http://www.adobe.com. Software Required: Adobe Acrobat (6.x, 7.x, or 8.x), or Adobe Acrobat Pro (6.x, 7.x, or 8.x), or the free Adobe Reader (6.x, 7.x, or 8.x) - 8.x is preferred ArcGIS 9.1 or later preferred, older versions may also work