Gulf of Mexico Region -- Highlighting Low-Lying Areas Derived from USGS Digital Elevation Data By John J. Kosovich 2008 U.S. Geological Survey Scientific Investigations Map 3048 I. SUMMARY: In support of U.S. Geological Survey (USGS) disaster preparedness efforts, this map depicts a color shaded relief representation of the area surrounding the Gulf of Mexico. 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 data) 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. Approximately one-half of the area shown on this map has DEM source data at a 30-meter resolution, with the remaining half consisting of 10-meter contour-derived DEM data or higher-resolution LIDAR data. Areas below sea level typically are surrounded by levees or some other type of flood-control structures. 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 2005. II. DISCLAIMERS: 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. This database, identified as SIM 3048, 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 SIM3048.pdf 00README.txt DataFiles.zip: gulf_ned90_b gulf_ned90_ft gulf_ned90_g gulf_ned90_r info stkgulf90 SIM3048_elevation_Gulf.pdf metadata metadata_gulf_ned90_b.txt metadata_gulf_ned90_ft.txt metadata_gulf_ned90_g.txt metadata_gulf_ned90_r.txt metadata_stkgulf90.txt IV. DATA FILE DESCRIPTIONS: gulf_ned90_b = Blue channel grid of the U.S. Gulf Coast derived from 30-meter National Elevation Dataset (NED) data which was resampled down to 90 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 region, 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 "SIM3048_elevation_Gulf.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. gulf_ned90_ft = Elevation grid of the U.S. Gulf Coast derived from 30-meter (1 arc-second) National Elevation Dataset (NED) data which was then resampled down to 90 meters and converted to integer-foot cell elevation values. 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. gulf_ned90_g = Green channel grid of the U.S. Gulf Coast derived from 30-meter National Elevation Dataset (NED) data which was resampled down to 90 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 region, 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 "SIM3048_elevation_Gulf.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. gulf_ned90_r = Red channel grid of the U.S. Gulf Coast derived from 30-meter National Elevation Dataset (NED) data which was resampled down to 90 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 region, 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 "SIM3048_elevation_Gulf.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 stkgulf90 = R,G,B grid stack of the three "gulf_ned90_"r,g,b grids (can be viewed as a three-band raster in ArcMap) SIM3048_elevation_Gulf.pdf = Explanation of elevation color ranges used for the Gulf of Mexico dataset V. SYSTEM REQUIREMENTS: The .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 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 3048 To access the data: The data files can be downloaded via the web from http://pubs.usgs.gov/sim/3048 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