Reproduced GMT Terrain Data Summary

Source: Internet
Author: User
Tags dbase radar

Reproduced GMT Terrain Data Summary
Original address:GMT Terrain Data Summary JasonReprint: Http:// currently exposed to the terrain data are mainly three kinds: Etopo, GTOPO30 and Srtm. Sort from low to high by precision as follows:
etopo5 of etopo5:gmt griddata etopo2:gmt etopo2v2 etopo1:gmt grid data ETOPO1 GTOPO30:GMT grid Data GTOPO30srtm30_plus: Global topographic fluctuations data: Srtm30_plus SRTM3: High-precision terrain grid data SrtmASTER Gdem: Global Digital elevation data: ASTER gdem

The Etopo data contains global topographic and seawater depth data, and GTOPO30 data contains global topographic data;srtm30_plus accuracy: 30 arc seconds, mesh accuracy approx. 1 km, including global topography and ocean depth data, Most regions use global topographic data in SRTM30, high latitude regions using GTOPO30 data (no SRTM data), The seabed topography data from 81 degrees to 81 degrees north latitude are derived from the global 1 data of Smith and Sandwell ; SRTM3 data contains terrain data for most regions of the world. The ASTER gdem data covers all land areas between northern latitude 83° to south latitude 83°, reaching 99% of the Earth's terrestrial surface. For global scale or large-scale topographic maps, ETOPO1 data can be used, GTOPO30 data can be used for areas with a degree of *10 of 3 degrees * 3 degrees-10 degrees, and SRTM3 data can be used for areas below 3 degrees of degree.ETOPO5 is a global topographic and bathymetric data with a grid sampling interval of 5 arcs, which has been replaced by higher precision ETOPO1, but the accuracy of the 5 arc is sufficient when plotting large area topography (e.g. global); Etopo2v2 is similar to ETOPO5, and is also the elevation + seabed topographic data with a sampling interval of 2 arc points; The etopoO1 contains global topography and ocean depths with a sampling interval of 1 arcs, which is currently the highest precision global relief data; GTOPO30 is a global digital elevation model published by the USGS with a sampling interval of 30 arc seconds; SRTM, all called Shuttle Radar Topography Mission, the project obtained radar imagery data from 60 degrees north latitude to 60 degrees south, and further processed the digital terrain Elevation model (DEM), now the SRTM topographic product data. 

 ETOPO1:It is divided into two versions, Ice surface and bedrock, and two versions are basically the same. The difference is that when dealing with the topography of Antarctica and Greenland, the former gives the elevation after adding the ice cover layer, which gives the elevation of the rock bed. For each version is subdivided into grid-registered and cell-registered, where grid-registered is the authoritative version, cell-registered is a derivative version, It is therefore recommended to download the grid-registered version. In each sub-version there are multiple data formats, Netcdf,binary, Xyz,tiff. I chose the binary format of the grid-registered version. 

Download: Http:// Bin is a binary network file,. HDR is the header filecopy the. bin to/usr/local/gmt-4.5.9/share/dbase:sudo cp etopo1_ice_g_i2.bin/usr/local/gmt-4.5.9/share/dbase

Modify "ETOPO1 Ice Surface" "M"-r-180/180/-90/90-i1m GG I 1 0-32768 etopo1_ice_g_i2.bin LSimilarly, for bedrock version of grid data, its is:ten "ETOPO1 bedrock" "M"-r-180/180/-90/90-i1m GG I 1 0-32768 etopo1_bed_g_i2.bin LIf you are downloading a grid file in NETCDF format, you need to convert the data to binary format using the following command:Grdreformat etopo1_ice_g_gmt4.grd etopo1_ice_g_i2.bin=bs-n-vPaint Test:#!/bin/bashverbose=-v#verbose=grdraster 9-rg-i2m-gout.grd $verbosemakecpt-cglobe-t-10500/8000/1000-z $verbose > Colors.cptgrdimage out.grd-ba60g30-rg-yc-xc-jn0/25c-ccolors.cpt-k $verbose > etopo5.pspsscale-ba2500f500::/: "M" :-ccolors.cpt-d12.5c/-2c/15c/.35ch-o $verbose >> etopo5.psrm out.grd colors.cpt 

GTOPO30: Download: Copy: Copy all dem files to/share/dbase modify GTOPO30 n90-n4011 " GTOPO30 w180n90 "" M "-r-180/-140/40/90-i0.5m PG I 1 0-9999 w180n90. DEM B12 "GTOPO30 w140n90" "M"-r-140/-100/40/90-i0.5m PG I 1 0-9999 w140n90. DEM B13 "GTOPO30 w100n90" "M"-r-100/-60/40/90-i0.5m PG I 1 0-9999 w100n90. DEM B14 "GTOPO30 w060n90" "M"-r-60/-20/40/90  -i0.5m PG I 1 0-9999 w060n90. DEM B15 "GTOPO30 w020n90" "M"-r-20/20/40/90-i0.5m PG I 1 0-9999 w020n90. DEM B16 "GTOPO30 e020n90" "M"-r20/60/40/90-i0.5m PG I 1 0-9999 e020n90. DEM B17 "GTOPO30 e060n90" "M"-r60/100/40/90-i0.5m PG I 1 0-9999 e060n90. DEM B18 "GTOPO30 e100n90" "M"-r100/140/40/90  -i0.5m PG I 1 0-9999 e100n90. DEM B19 "GTOPO30 e140n90" "M"-r140/180/40/90  -i0.5m PG I 1 0-9999 e140n90. DEM b # GTOPO30 n40-s1020 "GTOPO30 w180n40" "M"-r-180/-140/-10/40-i0.5m PG I 1 0-9999 w180n40. DEM B21 "GTOPO30 w140n40" "M"-r-140/-100/-10/40-i0.5m PG I 1 0-9999 w140n40. DEM B22 "GtopoW100n40 "" M "-r-100/-60/-10/40-i0.5m PG I 1 0-9999 w100n40. DEM B23 "GTOPO30 w060n40" "M"-r-60/-20/-10/40-i0.5m PG I 1 0-9999 w060n40. DEM B24 "GTOPO30 w020n40" "M"-r-20/20/-10/40  -i0.5m PG I 1 0-9999 w020n40. DEM B25 "GTOPO30 e020n40" "M"-r20/60/-10/40-i0.5m PG I 1 0-9999 e020n40. DEM B26 "GTOPO30 e060n40" "M"-r60/100/-10/40  -i0.5m PG I 1 0-9999 e060n40. DEM B27 "GTOPO30 e100n40" "M"-r100/140/-10/40-i0.5m PG I 1 0-9999 e100n40. DEM B28 "GTOPO30 e140n40" "M"-r140/180/-10/40-i0.5m PG I 1 0-9999 e140n40. DEM b # GTOPO30 s10-s6029 "GTOPO30 w180s10" "M"-r-180/-140/-60/-10-i0.5m PG I 1 0-9999 w180s10. DEM B30 "GTOPO30 w140s10" "M"-r-140/-100/-60/-10-i0.5m PG I 1 0-9999 w140s10. DEM B31 "GTOPO30 w100s10" "M"-r-100/-60/-60/-10-i0.5m PG I 1 0-9999 w100s10. DEM B32 "GTOPO30 w060s10" "M"-r-60/-20/-60/-10-i0.5m PG I 1 0-9999 w060s10. DEM B33 "GTOPO30 w020s10" "M"-r-20/20/-60/-10-i0.5m PG I 1 0-9999 w020s10. DEM B34 "GTOPO30 e020s10" "M"-r20/60/-60/-10 &nbSp;-i0.5m PG I 1 0-9999 e020s10. DEM B35 "GTOPO30 e060s10" "M"-r60/100/-60/-10-i0.5m PG I 1 0-9999 e060s10. DEM B36 "GTOPO30 e100s10" "M"-r100/140/-60/-10-i0.5m PG I 1 0-9999 e100s10. DEM B37 "GTOPO30 e140s10" "M"-r140/180/-60/-10-i0.5m PG I 1 0-9999 e140s10. DEM b # GTOPO30 s60-s9038 "GTOPO30 w180s60" "M"-r-180/-120/-90/-60-i0.5m PG I 1 0-9999 w180s60. DEM B39 "GTOPO30 w120s60" "M"-r-120/-60/-90/-60-i0.5m PG I 1 0-9999 w120s60. DEM B40 "GTOPO30 w060s60" "M"-r-60/0/-90/-60  -i0.5m PG I 1 0-9999 w060s60. DEM B41 "GTOPO30 w000s60" "M"-r0/60/-90/-60-i0.5m PG I 1 0-9999 w000s60. DEM B42 "GTOPO30 e060s60" "M"-r60/120/-90/-60-i0.5m PG I 1 0-9999 e060s60. DEM B43 "GTOPO30 e120s60" "M"-r120/180/-90/-60-i0.5m PG I 1 0-9999 e120s60. DEM B

DescriptionThe world is divided into 33 blocks, as shown, latitude 90 degrees to south latitude 60 degrees divided into 3 parts, each latitude 50 degrees, 40 degrees, a total of 3*9=27 blocks; near Antarctica 60 degrees to 90 degrees, 60 degrees, 6 blocks, a total of 33 blocks. Sampling Interval 30 arc second, that is 0.008333333333333 degrees, the world is divided into 21600 rows, 43200 columns. The coordinate reference is WGS84; its value is the distance from the vertical direction of the sea level, that is, the altitude, in M, and the elevation range 407 to 8752, which does not contain the ocean depth information, the negative value should be the altitude of the continental shelf, the sea elevation is marked by 9999, the coastline to the continental elevation of at least 1 ; less than 1 square kilometers of the island is not considered; the file has a filename in the upper-left corner of the block; file suffix: dem is the data elevation model; the other files are some auxiliary information; dimension 50 degrees * Longitude 40 degrees File Size: 57600000 bytes Dimension 30 degrees * Longitude 60 degrees File size: 28800000 bytes

Other Notes:These dem files are stored as pixel registration format data values as signed 16-bit integers that data are Big-endian

Drawing test:#!/bin/bashid=11range=-180/-140/40/90b=a10g10inc=0.5mps=${id}.psverbose=-v#verbose=grdraster $ID-r$range-i$ INC-GOUT.GRD $verbosemakecpt-ctopo-t1/8000/1000-z$verbose > Colors.cptgrdimage out.grd-b$b-r$range-yc-xc-jq15c- CCOLORS.CPT $verbose > $PS rm out.grd Colors.cpt This is only the first chunk of the terrain, if you need to draw multiple chunks at the same time, you need to call Grdraster multiple times to extract the mesh from different grid files, and then paste the grdpaste into a grid and then plot.

Antarctic RegionThere is also a special elevation data antarcps.dem in the Antarctic region, which contains the data of six blocks in the S60-S90 region, but is a stereoscopic projection with polar coordinates. Thus the horizontal axis range is ( -2700,2700) and the Ordinate range is ( -2700,2700). This is a bit of a hassle to deal with.

 SRTM:SRTM terrain data consists of two main types of data: SRTM3 and SRTM1. The SRTM3 accuracy is 3 arc seconds, which is 90m a point, including Africa, North America, South America, Eurasia, Australia and some islands; the SRTM1 accuracy is 1 arc seconds, or 30m a point, only in the United States; All data is divided into 1 degree degrees of units, totaling tens of thousands of data files. The file name represents the position of the lower-left corner of the cell, the data file names downloaded from different websites are different, but the file name is similar to the n37w105 data file, the coordinates of the lower left corner of the cell are (37n,105w), each SRTM3 data file contains 1201*1201 sample points, the elevation data is in M, The reference geoid is the WGS84 geoid model, and the grid is divided into gridlineregistration mode, so that the north-south side and the left and right side of the unit coincide with the adjacent units.

Data Download: Computer Network Information Center of CAS provides: Geotiff and ARCASCII Format data, the data is 5 degrees of the degree of a single unit, rather than the standard 1 degrees, eliminating the user to do mesh merging trouble; GMT can handle the ARCASCII format, However, the GeoTiff format cannot be processed, so the following is only used in ARCASCII format; in China, there are also some derivative data, such as slope, aspect, slope position, the data format is IMG format, the details are unknown;

Data Conversion:Convert arc ASCII format to GMT grid file: Xyz2grd srtm_63_02.asc-gstrm_63_02.grd-e-V

Drawing Examples:R=130/135/50/55B=A1F0.5WSENJ=Q4IXYZ2GRD srtm_63_02.asc-gstrm_63_02.grd-e-v#xyz2grd n52e130.hgt-gn52e130.grd-i3c/ 3C-R$R-N-32768-ZTLHW-VGRD2CPT n52e130.grd-cnrwc.cpt > Colors.cptgrdimage n52e130.grd-r$r-ccolors.cpt-b$b:. SRTM3:-j$j-k>

If this is the standard data downloaded by the USGS, example:The larger Kunlung domain, the downloaded data is n37e085.hgt and N37E086.HGT2 files. #First use xyz2grd to convert the binary hgt file into a grd file used by GMT, or an NC suffix. XYZ2GRD N37E085.HGT-GG001.GRD-I3C-R85/86/37/38-N-32768-ZTLHWXYZ2GRD N37E086.HGT-GG002.GRD-I3C-R86/87/37/38- n-32768-ztlhw# Merging GRD files grdpaste g001.grd g002.grd-ga1.grdmakecpt-cglobe-t-500/7000/500-z > Mydata.cptgrdgradient using Grdimage to draw a color map grdimage A1.GRD-R85/87/37/38-YC-XC-JM10I-CMYDATA.CPT-ICHINA.G > World1.pspscoast-r-j-di-n1-a1000-b0.5g0.5/0.5g0.5-w0.25p-o-k >>world1.pspsscale-ba2500f500 ::/: "M":-cmydata.cpt-d12.5c/-2c/15c/.35ch-o-U "author:yanglei" >> World1.psdel *.cpt *.int 

ASTER GdemAstergdem, a global digital elevation model for advanced Spaceborne Thermal Emission and reflection Radiometer, is a digital elevation dem, like SRTM, with a global spatial resolution of 30 meters. The data is based on detailed observations of NASA's new generation of ground observation satellite Terra. The data covers all land areas between latitude 83° to south latitude 83°, reaching 99% of the Earth's terrestrial surface. (Excerpt from Baidu Encyclopedia). Claims to be "the most complete global topographic data yet". ASTER Gdem: Spatial resolution: 1 radians seconds (approx. 30 m), accuracy: Vertical accuracy 20 m, horizontal accuracy 30 m, latitude coverage for SRTM data is [ -60,60],astergdem data latitude coverage of [ -83,83] The spatial resolution of the SRTM is generally 90m, and only the data in the United States has a spatial resolution of 30m; Astergdem has a spatial resolution of 30m; Website: needs to be registered, You can download the data for free, click "Search" to enter the data selection interface, the data is divided into 1 degrees of the block, each chunk file name in the lower left corner of the section of the latitude and longitude values to name, the data selection interface has four ways to select the block, the interface design is not very accustomed to watch English; data can be downloaded separately can also be downloaded in bulk; the downloaded file is a zip archive containing two files: Dem and num, both of which are GeoTiff formats, DEM data is digital elevation data, and NUM data is also known as the QA file, the quality evaluation file, It contains information such as the source of each point's elevation data, which is generally not used; convert it to GMT-recognizable NETCDF format using the tools provided by Gdal: gdal_translate-of GMT astgtm2_n36e111_dem.tifastgtm2_ N36e111_dem.grd

Reproduced GMT Terrain Data Summary

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