Valerie Paskevich 200508 1.0 remote-sensing image Open-File Report 2005-1001 Woods Hole Science Center, Woods Hole, MA U.S. Geological Survey, Coastal and Marine Geology Program http://pubs.usgs.gov/of/2005/1001/data/basemaps/srtm30plus/srtm30plus-na_pctshade.zip http://pubs.usgs.gov/of/2005/1001/htmldocs/datacatalog.htm L.J. Poppe S.J. Williams V.F. Paskevich 2005 1.0 Open-File Report 2005-1001 Woods Hole Science Center, Woods Hole, MA U.S. Geological Survey, Coastal and Marine Geology Program Publication and data are released via DVD-ROM media. This digital publication may also be available via the web at pubs.usgs.gov http://pubs.usgs.gov/of/2005/1001/ srtm30plus-na_pctshade.tif Joseph J. Becker and David T. Sandwell at the Scripps Oceanographic Institute have generated a dataset of world-wide coverage combining NASA's Shuttle Radar Topography Mission (SRTM) obtained elevation data and Smith and Sandwell global 2-minute bathymetry. This data set provides a global composite of elevation that can be utilized to create elevation/bathymetry visualization. The Shuttle Radar Topography Mission is a collaborative project between NASA, the National Imagery and Mapping Agency (NIMA), and the German and Italian space agencies to map the elevation of a large part of the globe. SRTM consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February of 2000. The instrument operated virtually flawlessly and imaged 99.96% of the targeted landmass at least one time, 94.59% at least twice and about 50% at least three or more times. The goal was to image each terrain segment at least twice from different angles (on ascending, or north-going, and descending orbit passes) to fill in areas shadowed from the radar beam by terrain. The 'targeted landmass' consisted of all land between 56 degrees south and 60 degrees north latitude, which comprises almost exactly 80% of the total landmass. While SRTM30 has the same resolution as GTOPO30, it can be considered a more accurate global digital data set compared to GTOPO30 because of its seamless and uniform representation, due to the fact that it was created over a short period of time from a single source rather than from the numerous sources spanning many decades that went into creating the GTOPO30 data set. This data set does not provide the high resolution SRTM elevation of the original one degree datasets. Sample spacing for the original individual data points is either 1 arc-second or 3 arc-seconds, referred to as SRTM-1 and SRTM-3, respectively. The user may visit ftp://e0mss21u.ecs.nasa.gov/srtm/ or ftp://e0mss21u.ecs.nasa.gov/srtm/ to obtain the higher resolution datasets. This image provides a broad scale view of the world topography (elevation and bathymetry) on which other Geographic Information System (GIS) data layers may be co-located and viewed. These data are intended for science researchers, students, policy makers, and the general public. The data can be used with geographic information systems (GIS) software to display geologic and oceanographic information. While SRTM30 has the same resolution as GTOPO30, it can be considered a more accurate global digital data set compared to GTOPO30 because of its seamless and uniform representation, due to the fact that it was created over a short period of time from a single source rather than from the numerous sources spanning many decades that went into creating the GTOPO30 data set. However, it must be noted that the SRTM30 does not cover the poles north and south of approximately 60° latitude. Therefore, data for Antarctica, for example, must be obtained from the GTOPO30 data set. en 2005 publication date Complete None planned -180 -30 90 0 -179.995834-29.993501-0.03389889.995834 General U.S. Geological Survey USGS Coastal and Marine Geology Program CMGP Woods Hole Science Center WHSC GeoTIFF image color-encoded shaded relief bathymetry topography SRTM30_PLUS Shuttle Radar Topography Mission ISO 19115 Topic Category oceans and estuaries elevation imageryBaseMapsEarthCover General North America United States Canada None Bathymetry is not to be used for navigational purposes. Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. Please recognize the U.S. Geological Survey (USGS) as the source of this information. All source data are derived from public domain sources and these data are also in the public domain. Valerie Paskevich U.S. Geological Survey Information Specialist, GIS Coordinator mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 x2281 (508) 457-2310 vpaskevich@usgs.gov http://pubs.usgs.gov/of/2005/1001/data/basemaps/srtm30plus/srtm30plus-na_pctshade-thumb.gif Thumbnail image showing extent and coverage of data layer. GIF Please credit Joseph J. Becker, David T. Sandwell for the compilation of the Land and Ocean data used as the source. Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.0.0.535 Raster DatasetOverview showing image extent and coverage of data layer.GIFhttp://pubs.usgs.gov/of/2005/1001/data/basemaps/srtm30plus/srtm30plus-na_pctshade.gif Elevation Data - Each SRTM data tile contains a mosaic of elevations generated by averaging all data takes that fall within that tile. Since the primary error source in synthetic aperture radar data is speckle, which has the characteristics of random noise, combining data through averaging reduces the error by the square root of the number of data takes used. In the case of SRTM the number of data takes could range from a minimum of one (in a very few cases) up to as many as ten or more. Land data are based on the 1-km averages of topography derived from the USGS SRTM30 grided DEM data product created with data from the NASA Shuttle Radar Topography Mission. GTOPO30 data are used for high latitudes where SRTM data are not available. Ocean data are based on the Smith and Sandwell global 2-minute grid between latitudes +/- 72 degrees. Higher resolution grids have been added from the LDEO Ridge Multibeam Synthesis Project and the NGDC Coastal Relief Model. Arctic bathymetry is from the International Bathymetric Chart of the Oceans (IBCAO) [Jakobsson et al., 2003]. 20 meters circular error at 90% confidence 16 meters linear error at 90% confidence Joseph J. Becker David T. Sandwell 200412 0.1 document La Jolla, CA Scripps Institution of Oceanography, University of California San Diego http://topex.ucsd.edu/WWW_html/srtm30_plus.html 1:1000 disc 200412 publication date srtm30plus This data consists of 33 files binary of global topography (elevation & bathymetry; 16-bit signed values). The individual files were downloaded via the web and combined to create a single raster coverage of world coverage. The grid resolution of the source data is 30 second which is roughly one kilometer. Thirty-three zip archive files of global topography were downloaded. The files were unzipped to create raw 16-bit binary data files. Each of the thirty-three files were imported into a separate PCI Geomatics database file. Importing the files into PCI allowed the ability to swap the bytes from a 16-bit Most-Significant-Bit order (MSB: Sun/Motorola) to a 16-bit Least-Significant-Bit order (LSB: Intel/VAX). Georeferencing information were added to each of the thirty-three files. 20050502 Valerie Paskevich U.S. Geological Survey Information Specialist, GIS Coordinator mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 x2281 (508) 457-2310 vpaskevich@usgs.gov A new PCI Geomatics database file was defined to combine the global dataset. The individual thirty-three files were mosaicked to create one world view. 20050502 srtm30plus.pix Valerie Paskevich U.S. Geological Survey Information Specialist, GIS Coordinator mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 x2281 (508) 457-2310 vpaskevich@usgs.gov The area of interest was extracted from the composite image. This was done to reduce the overall size of the image and to retain as much detail as possible. The 16-bit signed image data was transferred to the new database. srtm30plus.pix 20050504 srtm30plus-na.pix Valerie Paskevich U.S. Geological Survey Information Specialist, GIS Coordinator mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 x2281 (508) 457-2310 vpaskevich@usgs.gov Two additional 8-bit channel were added to the PCI database for future processing. The program REL was run to create an 8-bit shaded relief image based on the 16-bit signed image data. srtm30plus-na.pix 20050505 srtm30plus-na.pix Valerie Paskevich U.S. Geological Survey Information Specialist, GIS Coordinator mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 x2281 (508) 457-2310 vpaskevich@usgs.gov The shaded relief image was viewed in PCI Imageworks. A linear stretch enhancement was applied to the image and the resulting Look-up Table (LUT) saved in the database. srtm30plus-na.pix 20050505 srtm30plus-na.pix Valerie Paskevich U.S. Geological Survey Information Specialist, GIS Coordinator mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 x2281 (508) 457-2310 vpaskevich@usgs.gov The 8-bit shaded relief image had a linear stretch permanently applied to create a new, final image. srtm30plus-na.pix 20050505 srtm30plus-na.pix Valerie Paskevich U.S. Geological Survey Information Specialist, GIS Coordinator mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 x2281 (508) 457-2310 vpaskevich@usgs.gov The final 8-bit grey-scale, shaded relief image was exported to a GeoTIFF image srtm30plus-na.pix 20050505 srtm30plus-na.tif srtm30plus-na.tfw Valerie Paskevich U.S. Geological Survey Information Specialist, GIS Coordinator mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 x2281 (508) 457-2310 vpaskevich@usgs.gov The two source images were brought into Corel PhotoPaint. The color-encoded elevation image (strm30plus-na_color.tif) was overlaid on top of the shaded relief image (srtm30plus-na_shade.tif_. The color image was made 60% transparent to allow shading to be seen through the image. The two images were combined to create a single 24-bit image showing elevation based on color. srtm30plus-na_shade.tif srtm30plus-na_color.tif 20050505 srtm30plus-world_pctshade.tif srtm30plus-world_pctshade.tfw Valerie Paskevich U.S. Geological Survey Information Specialist, GIS Coordinator mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 x2281 (508) 457-2310 vpaskevich@usgs.gov Raster Pixel 10804 18001 1 0.0083330.0083338Upper LeftFALSENone3pixel codesFALSETIFF 0.008333 0.008333 Decimal degrees D_WGS_1984 WGS_1984 6378137.000000 298.257224 row and column0.0083330.008333 U.S. Geological Survey mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 (508) 457-2310 Downloadable Data Although this data set has been used by the U.S. Geological Survey (USGS), no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and/or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data or related materials. Trade, firm, or product names and other references to non-USGS products and services are provided for information only and do not constitute endorsement or warranty, express or implied, by the USGS, USDOI, or U.S. Government, as to their suitability, content, usefulness, functioning, completeness, or accuracy. TIFF GeoTIFF image Archive containing GeoTIFF image, world file and metadata. zip 556.503 556.503 http://pubs.usgs.gov/of/2005/1001/data/basemaps/srtm30plus/srtm30plus-na_pctshade.zipData are downloadable via the World Wide Web (WWW).DVD-ROM4.75GbytesUDF None This image is available as a GEOTIFF image with an accompanying world file. To utilize this data, the user must have an image viewer, image processing or GIS software package capable of importing a GeoTIFF image. 20050512 20050512 U.S. Geological Survey Valerie Paskevich Information Specialist, GIS Coordinator mailing and physical address

384 Woods Hole Road

Woods Hole MA 02543-1598 USA (508) 548-8700 x2281 (508) 457-2310 vpaskevich@usgs.gov FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 local time None None enhttp://www.esri.com/metadata/esriprof80.htmlESRI Metadata Profile Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.0.0.535srtm30plus-na_pctshade.tif-179.995834-29.99350189.995834-0.0338981ISO 19115 Geographic Information - MetadataDIS_ESRI1.0dataset002file://\\VALPASDTXP\D$\My Webs\texture\data\basemaps\srtm30plus\srtm30plus-na_pctshade.tifLocal Area Network556.503Raster Dataset21180010.008333unknown108040.008333unknown2005082407245900200508240724590020050824