SRTM30_PLUS: DATA FUSION OF SRTM LAND TOPOGRAPHY WITH MEASURED AND ESTIMATED SEAFLOOR TOPOGRAPHY SRTM30_PLUS V11. - November 29, 2014 David T. Sandwell dsandwell@ucsd.edu Chris Olson Amber Jackson Joseph J. Becker Rachael Munda rmunda@ucsd.edu> The SRTM30_PLUS is available in 2 formats. 1) topo30 format The subdirectory called topo30 has the data stored in a single large file of 2-byte integers in MSB format (i.e. big-endian). The grid spans 0 to 360 in longitude and -90 to 90 in latitude. The upper left corner of the upper left grid cell has latitude 90 and longitude 0. There are 43200 columns and 21600 rows. A matching source identification file (SID) called topo30_sid is also included. The sid numbers are stored as unsigned 2-byte integers. 2) srtm30 format The directory called srtm30 has the same data in original SRTM30 format consisting of 33 tiles is described below. DIRECTORIES data - 33 files of signed 2-byte integers for global elevation(> 0) and depth (<0). The global elevations are an exact copy of the SRTM30 grids provided at the following location. Our contribution is to fill the ocean areas with some estimate of depth. ftp://e0srp01u.ecs.nasa.gov sid - 33 files of unsigned 2-byte integers representing the source identification number for the data (0 - predicted depth). Soon we will make these data files available in an ASCII format. The file names indicate the boundaries of each tile Latitude Longitude Tile Minimum Maximum Minimum Maximum ------- ---------------- ---------------- w180n90 40 90 -180 -140 w140n90 40 90 -140 -100 w100n90 40 90 -100 -60 w060n90 40 90 -60 -20 w020n90 40 90 -20 20 e020n90 40 90 20 60 e060n90 40 90 60 100 e100n90 40 90 100 140 e140n90 40 90 140 180 w180n40 -10 40 -180 -140 w140n40 -10 40 -140 -100 w100n40 -10 40 -100 -60 w060n40 -10 40 -60 -20 w020n40 -10 40 -20 20 e020n40 -10 40 20 60 e060n40 -10 40 60 100 e100n40 -10 40 100 140 e140n40 -10 40 140 180 w180s10 -60 -10 -180 -140 w140s10 -60 -10 -140 -100 w100s10 -60 -10 -100 -60 w060s10 -60 -10 -60 -20 w020s10 -60 -10 -20 20 e020s10 -60 -10 20 60 e060s10 -60 -10 60 100 e100s10 -60 -10 100 140 e140s10 -60 -10 140 180 w180s60 -90 -60 -180 -120 w120s60 -90 -60 -120 -60 w060s60 -90 -60 -60 0 w000s60 -90 -60 0 60 e060s60 -90 -60 60 120 e120s60 -90 -60 120 180 _________________________________________________________________________________________ November 28, 2014 Version 11. has the identical format as previous versions. Enhancements from V10.0 1) The V23 global grabity model was used in the predicted topography 2) About 111 additional multibeam cruises were added. 3) All the multibeam were reprocessed to remove 500-m cells hafing fewer than 10 pings. This cleans up the bad pings on the outer beams and was neede for the development of SRTM15. _________________________________________________________________________________________ May 22, 2014 Version 10. has the identical format as previous versions. Enhancements from V9.0 1) 685 new multibeam cruises were added from the NGDC multibeam archive. 2) 104 tiles of multibeam grids were added from the Geosciences Australia released under the Creative Commons Attri bution 3.0 3) New multibeam grids from GEOMAR from the Southeast Pacific and Cape Verde 4) additional editing of all these data _________________________________________________________________________________________ December, 2013 Version 9.0 has the identical format as previous versions. Enhancements from V8.0 1) The predicted depth is based on the new V22 gravity model which includes all new data from Cryosat-2, Jason-1, and Envisat resulting in about a factor of 2 improvement in gravity accuracy. In addition both the gravity and the predicted depth have a filter wavelength that is about 2 km shorter than previous versions (i.e., 14 km wavelength instead of 16 km). 2) There has been a lot of editing of bad soundings especially on the continental margins where the deep holes were eliminated. 3) About 446 new JAMSTEC multibeam cruises were added. These data were sampled at 15 arcseconds to prepare for an SRTM15. _________________________________________________________________________________________ December 2012 Version 8.0 has the identical format as previous versions. Enhancements from V7.0 Arctic bathymetry north of 70 N is based on IBCAO V3.0 http://www.ngdc.noaa.gov/mgg/bathymetry/arctic/. Predicted depth based on new global Gravity V20.1. This included 2 years of altimetry data from CryoSat, 1.5 years from Envisat, and 120 days from Jason-1. A new A-coefficient for the downward continuation parameter was used based on a coherence analysis performed by Karen Marks. _________________________________________________________________________________________ December 2011 Version 7.0 has the identical format as previous versions. Enhancements from V6.0 include the addition of all US multibeam data stored at NGDC as of April 2011. Edited multibeam data from Ewing and Palmer cruises was provided by the Marine Geoscience Data System. http://www.marine-geo.org/index.php In addition a 500-m grid of Great Barrier Reef bathymetry from Rob Beaman http://e-atlas.org.au/content/gbr-jcu-bathymetry-gbr100 One other change as the latitude cutoff for the IBCAO Arctic grid was lowered ftom 80 N to 70 N. This eliminates some of the "orange peel areas of predicted depth between 70 and 80. _________________________________________________________________________________________ November 2009 Version 6.0 has the identical format as previous versions. This version includes a significant number of new depth soundings. This version is based on an more accurate prediction between gravity anomaly and depth. In addition is contains many more depth soundings than all previous versions and has extensive editing to remove blunders. _________________________________________________________________________________________ September 2009 Version 5.0 has the identical format as previous versions. This version includes a significant number of new depth soundings. A more complete description of the new data and processing was prepared for publication in early 2008. This is a collaborative effort between NGA, NOAA, NAVO and SIO. The predicted depths are based on the V16.1 gravity anomaly model in an adjacent directory. _________________________________________________________________________________________ May 2008 Version 4.0 has the identical format as previous versions. This version includes a significant number of new depth soundings, especially for depths between 0 and -300 m. A more complete description of the new data and processing will be prepared for publication in early 2008. This is a collaborative effort between NGA, NOAA, NAVO and SIO. The predicted depths are based on the V16.1 gravity anomaly model in an adjacent directory. This version has gone through 6 iterations of identifying bad tracks, editing the offending profiles and constructing a new grid. If you find anomalies (there are several remaining) please send an e-mail with the problem location and we will address it. _________________________________________________________________________________________ December 2007 Version 3.0 has the identical format as V1.0. On land areas (except Anartctica) the land data ov Version 3.0 are identical to Version 2.0 which are identical to Version 2 of the SRTM30 land data. 1) Ocean data The ocean data are based on V9.1 of our global predicted depth. This 1-minute grid includes a significant number of new depth soundings, especially for depths between 0 and -300 m. A more complete description of the new data and processing will be prepared for publication in early 2008. This is a collaborative effort between NGA, NOAA, NAVO and SIO. The predicted depths are based on the V16.1 gravity anomaly model in an adjacent directory. Please send comments to dsandwell@ucsd.edu. 2) Antarctica The land adat on Antarctica are from Digital Elevation Models of the Antarctic and Greenland Ice Sheets Using Data From ICESat John P. DiMarzio12, Anita C. Brenner23, Helen A. Fricker4, Jack L. Saba23, Bob E. Schutz5, Christopher A. Shuman2, H. Jay Zwally2 2007 Jan 5 DESCRIPTION OF THE DIGITAL ELEVATION MODELS The ICESat/GLAS Antarctic and Greenland Digital Elevation Models (DEMs) are polar-stereographic projection of the ICESat/GLAS elevation data in raster format. The elevation grids were used to compute the slope and slope azimuth grids. _________________________________________________________________________________________ July 2006 Version 2.0 has the identical format as V1.0. There are two main improvements: 1) The land data come from version 2 of the SRTM30 processing. Here is the information on SRTM V2 provided by Tom Farr of JPL on October 10, 2005. "NASA has released version 2 of the Shuttle Radar Topography Mission digital topographic data (also known as the "finished" version). Version 2 is the result of a substantial editing effort by the National Geospatial Intelligence Agency and exhibits well-defined water bodies and coastlines and the absence of spikes and wells (single pixel errors), although some areas of missing data ('voids') are still present. The Version 2 directory also contains the vector coastline mask derived by NGA during the editing, called the SRTM Water Body Data (SWBD), in ESRI Shapefile format. The data may be obtained by anonymous ftp to: e0srp01u.ecs.nasa.gov and moving to the directory srtm where both version 1 and version 2 directories may be found. Please read the appropriate documentation, also found in the directories." 2) We have added several new bathymetry grids derived from large multibeam surveys. The new data include a large IFREMER survey of the Southwest Indian Ridge provided by Mathilde Cannat, a compilation of the Lau Basin provided by Brian Taylor of SOEST, and a large survey of the Foundation Seamounts provided bu Marcia Maia at IFREMER. _________________________________________________________________________________________ SRTM30_PLUS V1.0 November 11, 2004 INTRODUCTION This data consists of 33 files of global topography in the same format as the SRTM30 products distributed by the USGS EROS data center. The grid resolution is 30 seconds which is roughly one kilometer.Land data are based on the 1-km averages of tropography derived from the USGS SRTM30 gridded 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 Multibeam Data. Arctic bathymetry is from the International Bathymetric Chart of the Oceans (IBCAO) [Jakobsson et al., 2003]. All data are derived from public domain sources and these data are also in the public domain.The pixel-registered data are stored in 33 files with names corresponding to the upper left corner of the array shown below. The USGS SRTM30 data and documentation is available at ftp://edcsgs9.cr.usgs.gov/pub/data/srtm/SRTM30 The US continental coastal multibeam data is available at www.ngdc.noaa.gov/mgg/coastal/coastal.html Data from Puerto Rico and Hawaii is -NOT- presently included. The ocean ridge multibeam data is available at www.ocean-ridge.ldeo.columbia.edu/general/html/home.html The artic ocean bathymetry is from http://www.ngdc.noaa.gov/mgg/bathymetry/arctic/arctic.html The Antarctica data (starting at 72S) is not very interesting; the terrestrial data is from GTOPO30, and the limited bathymetry is from JEBCO. _________________________________________________________________________________________ DATA FORMATS Data are provided as binary integers in exactly the same format as SRTM30. The files must be uncompressed with gzip and are 16-bit big endian byte order. These files can be used directly by ER_Mapper software using the header files stored in the subdirectory ermapper_headers. These files can be converted to Generic Mapping Tools (grd-netcdf) format using the scripts in the subdirectory grd. _________________________________________________________________________________________