全球地形资料img ETOPO1

This readme file contains information on the ETOPO1 binary grid formats. ETOPO1 comes in two different binary formats: 2-byte/16-bit integer (i2) and 4-byte/32-bit float (f4); float refers to the file format, not the elevation values in the grids, which have been rounded to whole integers for all versions. Each zip file contains the binary grid and an associated header file that describes the grid format. ESRI ArcGIS users should use the f4 version and convert using 'Float to Raster'. An example 4-byte float header file, of the ETOPO1 Ice Surface grid-registered grid (etopo1_ice_g_f4) is: ncols 21601 nrows 10801 xllcenter -180.00 yllcenter -90.00 cellsize 0.01666666667 NODATA_value -99999 byteorder LSBFIRST NUMBERTYPE 4_BYTE_FLOAT MIN_VALUE -10898.0 MAX_VALUE 8271.0 An example 2-byte integer header file, of the ETOPO1 Bedrock cell-registered grid (etopo1_bed_c_i2) is: NCOLS 21600 NROWS 10800 XLLCORNER -180.000000 YLLCORNER -90.000000 CELLSIZE 0.01666666667 NODATA_VALUE -32768 BYTEORDER LSBFIRST NUMBERTYPE 2_BYTE_INTEGER ZUNITS METERS MIN_VALUE -10803 MAX_VALUE 8333 ETOPO1 1 Arc-Minute Global Relief Model