Color Shaded Relief Maps of the U.S. ------------------------------------ by Ray Sterner, Johns Hopkins University Applied Physics Laboratory Overview -------- This directory contains color shaded relief maps of the U.S. Currently two complete maps are available. The original map is version 1.0 and shows coastlines, boundaries, and rivers. Elevation is shown by color bands with the topography shaded within each band. Version 2.1 uses a continuous color shading and has more subdued colors. Coastlines and boundaries are also more subdued. Rivers are not shown on version 2.1. Each map consists of 60 GIF images that cover most of the continental U.S. Both maps show an amazing amount of detail, showing the geomorphology of the U.S. as seldom ever seen. If the borders were removed from each section and the sections were placed in a mosaic the total map would be 6600 pixels East/West by 3470 pixels North/South. This has been done, see: http://www.research.digital.com:80/SRC/personal/Andrew_Birrell/reliefMaps/ In version 1.0 each color band covers an elevation range of 1000 feet. The total space needed for the 60 images is 8.1 Mb for version 1.0 and 11.7 Mb for version 2.0. Both maps cover the range 65 to 125 degrees West longitude and 25 to 50 degrees North latitude. The GIF images -------------- Individual GIF images cover a 5 deg by 5 deg area. Some images are blank but are included for completeness. Version 1: Each image is 656 by 800 pixels with the map area covering 550 by 694 pixels. The image coordinates of the map area (excluding the grid) are (81,81) for the lower left corner to (630,774) for the upper right corner, where (0,0) is the lower left corner of the GIF image. Version 2: Each image is 656 by 800 pixels with the map area covering 546 by 689 pixels. The image coordinates of the map area (excluding the grid) are (81,81) for the lower left corner to (626,769) for the upper right corner. The map area may be cut out and pieced together to form larger areas or to better show areas near image boundaries. The maps should be overlapped on the grids. The image files are named as follows. Version 1.0 names are NNWWWDNDW.gif where NN=north lat, WWW=west long of SE corner of image. DN=size in Lat, DW=size in Long (deg). The area size is included so that in the future images covering specific areas of interest may be included. Version 2.0 names are the same except for a v2 before .gif. An index map has been provided by Ken Shirriff of Berkeley. It is an 800x400 GIF image named index.gif. The index uses version 1.0 colors. The ocean was originally green instead of blue because with 20 foot vertical resolution 0 elevation extends inland from the coast in lowlying areas, so coloring 0 elevation blue would include some land areas. However, version 1.0 has had the ocean and major lakes colored blue. This was done by Greg LaCoste of Seismotectonics, Bureau of Reclamation, Denver CO. Thanks for your help Greg. *** Note: version 1.0 maps no longer have a common color table. This was a side effect of coloring the water areas. Cities and roads are not shown on the map for two reasons. First, the data was not readily available. Second, I wouldn't use it if it was since it would obscure details. Even the rivers and boundaries are somewhat of a compromise (on version 1.0). Some notes on version 2.0 ------------------------- Version 2.0 of the map may be more useful for showing landforms. The coastlines and boundaries were purposely subdued to minimize interference on the images. Rivers are not shown. Often their valleys are easily seen on the version 2.0 images. Accessing the ftp site (see also Mirror Sites below) ---------------------- ftp fermi.jhuapl.edu (128.244.147.18. fermi is an alias for nansen). For Name type: anonymous For Password enter: your email address (ex: sterner@tesla.jhuapl.edu). Change directory by entering: cd pub/gifmap Set the correct transfer type: ascii (for readme.txt) or binary (for the *.gif files). To get a file enter: get filename When finished enter: bye. Get the ascii file readme.txt for more details. Some suggestions for a first look: index.gif by Ken Shirriff of Berkeley shows what is covered by each gif image. 301150505.gif: shows the Salton Sea area, Los Angeles area, San Andreas rift zone, ... 351100505.gif: shows the Grand Canyon, Coconino and Kaibab Plateaus, some of the basin and range, the San Rafael swell, ... Mirror sites ------------ Anonymous ftp sites: src.doc.ic.ac.uk:geology/maps/gifmaps provided by Lee McLoughlin Mosaic home pages: http://www.doc.ic.ac.uk/public/geology/maps/gifmaps/ by Lee McLoughlin http://ageninfo.tamu.edu/apl-us/ by Hal Mueller The data -------- The elevation data has a horizontal resolution of 1/2 arc minute for both East/West and North/South, and a vertical resolution of 20 feet. (This is NOT the same as ETOPO5 data as previously stated) The vector data (coastlines, rivers, boundaries) are from World Data Bank II. There are some areas where the two data bases have minor differences in positioning, most noticable for some rivers. The errors are not constant over the map and no attempt has been made to correct for them in this version of the map. Map projection and shading -------------------------- The map projection is the simplest possible one, Cylindrical Equidistant. The shape is corrected for 37.5 deg North latitude (the average of 25 and 50 deg lat). This is not the best projection as far as distortion goes but it has the big advantage of making it easy to write applications that can plot objects given their coordinates or read coordinates from the image. The rectangular projection also makes it easier to combine the map portions of the images into a mosaic. The lighting is from the Northwest. Features with slopes toward or away from the lighting direction are shown well. Features with slopes at right angles to this direction may not be shown at their best. The low sun angle is a compromise between showing details in low relief areas and hiding too much in shadowed areas. Creating the map ---------------- The map was created using the IDL programming language running on an HP 735 workstation. IDL includes extensive map projection support, but it was not used for this simple projection. Creating a mosaic ----------------- With an image processing program it should be possible to cut and combine several map images to cover a larger area. The image coordinates of the map part of each image are given above. If the images are cut correctly it should be possible to keep a labeled border around the resulting larger image. If a complete mosaic is made the elevation key should be place where the 30 N Lat/70 W Long image would be since it is completely blank. Images are included to fill out the rectangular region from 60 to 125 W long and 25 to 50 N lat. Color Keys ---------- Version 1.0 color key: elev_key.gif. Version 2.0 color key: elev_keyv2.gif. In words the version 1.0 colors are: Elevation Color --------- ----- Below 0 White 0 to 1000 Green 1000 to 2000 Yellow 2000 to 3000 Orange 3000 to 4000 Red 4000 to 5000 Magenta 5000 to 6000 Cyan 6000 to 7000 Pastel Green 7000 to 8000 Pastel Yellow 8000 to 9000 Pastel Orange 9000 to 10000 Pastel Red 10000 to 11000 Pastel Magenta 11000 to 12000 Pastel Cyan Above 12000 White Request for image captions -------------------------- A set of caption files for the images is intended. This will require the help of internet users familiar with locations in the images. Information should be relevant to visible features. Items of interest are geology, history, geography, resources, national parks, scenic areas, and so on. More detailed guidelines are given in the text file caption_guide.txt. Other information ----------------- A newer set of maps which show individual states may be viewed at http://fermi.jhuapl.edu/states/states.html Version 1.0 maps will eventually be dropped. Ray Sterner sterner@tesla.jhuapl.edu Johns Hopkins University North latitude 39.16 degrees. Applied Physics Laboratory West longitude 76.90 degrees. Laurel, MD 20723-6099