etopo

Read gridded global relief data (ETOPO products)

Syntax

[Z, refvec] = etopo
[Z, refvec] = etopo(samplefactor)
[Z, refvec] = etopo(samplefactor, latlim, lonlim)
[Z, refvec] = etopo(folder, ...)
[Z, refvec] = etopo(filename, ...)
[Z, refvec] = etopo({'etopo5.northern.bat', 'etopo5.southern.bat'}, ...)

Description

[Z, refvec] = etopo reads the ETOPO data for the entire world from the ETOPO data in the current folder. The etopo function searches the current folder first for ETOPO1c binary data, then ETOPO2V2c binary data, then ETOPO2 (2001) binary data, then ETOPO5 binary data, and finally ETOPO5 ASCII data. Once the function finds a case-insensitive file name match, it reads the data. See the table Supported ETOPO Data File Names for a list of possible file names. The etopo function returns the data grid, Z, as an array of elevations. Data values, in whole meters, represent the elevation of the center of each cell. refvec, the associated three-element referencing vector, geolocates Z.

[Z, refvec] = etopo(samplefactor) reads the data for the entire world, downsampling the data by samplefactor. The scalar integer samplefactor when equal to 1 gives the data at its full resolution (10800 by 21600 values for ETOPO1 data, 5400 by 10800 values for ETOPO2 data, and 2160 by 4320 values for ETOPO5 data). When samplefactor is an integer n greater than one, the etopo function returns every nth point. If you omit samplefactor or leave it empty, it defaults to 1. (If the etopo function reads an older, ASCII ETOPO5 data set, then samplefactor must divide evenly into the number of rows and columns of the data file.)

[Z, refvec] = etopo(samplefactor, latlim, lonlim) reads the data for the part of the world within the specified latitude and longitude limits. Specify the limits of the desired data as two-element vectors of latitude, latlim, and longitude, lonlim, in degrees. Specify the elements of latlim and lonlim in ascending order. Specify lonlim in the range [0 360] for ETOPO5 data and [-180 180] for ETOPO2 and ETOPO1 data. If latlim is empty, the latitude limits are [-90 90]. If lonlim is empty, the file type determines the longitude limits.

[Z, refvec] = etopo(folder, ...) allows you to use the variable folder to specify the path for the ETOPO data file. Otherwise, the etopo function searches the current folder for the data.

[Z, refvec] = etopo(filename, ...) reads the ETOPO data from filename. The variable filename, a case-insensitive string, specifies the name of the ETOPO file, as referenced in the ETOPO data file names table. Include the folder name in filename or place the file in the current folder or in a folder on the MATLAB path.

[Z, refvec] = etopo({'etopo5.northern.bat', 'etopo5.southern.bat'}, ...) reads the ETOPO data from the specified case-insensitive ETOPO5 ASCII data files. Place the files in the current folder or in a folder on the MATLAB path.

Definitions

According to the National Geophysical Data Center (NGDC) Web site, ETOPO models combine regional and global land topography and ocean bathymetry data from many data sources. ETOPO1, the most recent model, has an Ice Surface version showing the top of the Antarctic and Greenland ice sheets and a Bedrock version showing the bedrock below the ice sheets. For detailed information about the data sources used to create the ETOPO1 model, see the NGDC Web site. NGDC lists the ETOPO2 and ETOPO5 models as deprecated but still available.

ModelCell SizeDate Available
ETOPO11-arc-minuteMarch 2009
ETOPO2v22-minute2006
ETOPO22-minute2001
ETOPO55-minute1988

Examples

Read and display ETOPO2V2c data from the file 'ETOPO2V2c_i2_LSB.bin' downsampled to half-degree cell size and display the boundary of the land areas.

samplefactor = 15;
[Z, refvec] = etopo('ETOPO2V2c_i2_LSB.bin', samplefactor);
figure
worldmap world
geoshow(Z, refvec, 'DisplayType', 'texturemap');
demcmap(Z, 256);
geoshow('landareas.shp', 'FaceColor', 'none', ...
   'EdgeColor', 'black');

Read and display ETOPO1 data for a region around Australia.

figure
worldmap australia
mstruct = gcm;
latlim = mstruct.maplatlimit;
lonlim = mstruct.maplonlimit;
[Z, refvec] = etopo('etopo1_ice_c.flt', 1, latlim, lonlim);
geoshow(Z, refvec, 'DisplayType', 'surface');
demcmap(Z, 256);

More About

expand all

Tips

Supported ETOPO Data File Names

FormatFilenames
ETOPO1c (cell)
  • etopo1_ice_c.flt

  • etopo1_bed_c.flt

  • etopo1_ice_c_f4.flt

  • etopo1_bed_c_f4.flt

  • etopo1_ice_c_i2.bin

  • etopo1_bed_c_i2.bin

ETOPO2V2c (cell)
  • ETOPO2V2c_i2_MSB.bin

  • ETOPO2V2c_i2_LSB.bin

  • ETOPO2V2c_f4_MSB.flt

  • ETOPO2V2c_f4_LSB.flt

  • ETOPO2V2c.hdf

ETOPO2 (2001)
  • ETOPO2.dos.bin

  • ETOPO2.raw.bin

ETOPO5 (binary)
  • ETOPO5.DOS

  • ETOPO5.DAT

ETOPO5 (ASCII)
  • etopo5.northern.bat

  • etopo5.southern.bat

  • For details on locating ETOPO data for download over the Internet, see the following documentation at the MathWorks Web site: Finding Geospatial Data.

References

[1] "2-minute Gridded Global Relief Data (ETOPO2v2)," U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Geophysical Data Center, 2006.

[2] Amante, C. and B. W. Eakins, "ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis," NOAA Technical Memorandum NESDIS NGDC-24, March 2009.

[3] "Digital Relief of the Surface of the Earth," Data Announcement 88-MGG-02, NOAA, National Geophysical Data Center, Boulder, Colorado, 1988.

[4] "ETOPO2v2 Global Gridded 2-minute Database," National Geophysical Data Center, National Oceanic and Atmospheric Administration, U.S. Dept. of Commerce.

See Also

| |

Was this topic helpful?