The first row in the file is very likely the northernmost one, i.e. The data are stored in row major order (all the data for row 1, followed by all the data for row 2, etc.)
#PUREBASIC INTEGER FULL#
The quickstart documentation lacks information about how rows and columns are organized in the file, but in the full documentation it is stated that The same calculation for longitude results in grid column 1104. Divided by three and rounded to the closest integer gives a grid row of 500. Let's find out which pixel you are interested in. Data voids are assigned the value -32768. Heights are in meters referenced to the WGS84/EGM96 geoid. DEC Alpha, most PCs and Macintosh computers built after 2006 use Intel ("little-endian") order so some byte-swapping may be necessary. Theīytes are in Motorola "big-endian" order with the most significant byte first,ĭirectly readable by systems such as Sun SPARC, Silicon Graphics and Macintosh computers using Power PC processors. To be more exact, these coordinates refer to the geometric center of the lower left pixel, which in the case of SRTM3 data will be about 90 meters in extent. N37W105 has its lower left corner at 37 degrees north latitude and 105 degrees west longitude.
and its territories and possessions) with data sampled at one arc-second intervals in latitude and longitude, and SRTM3 (for the world) sampled at three arc-seconds.ĭata are divided into one by one degree latitude and longitude tiles in "geographic" projection, which is to say a raster presentation with equal intervals of latitude and longitude in no projection at all but easy to manipulate and mosaic.įile names refer to the latitude and longitude of the lower left corner of the tile - e.g. SRTM data are distributed in two levels: SRTM1 (for the U.S.
#PUREBASIC INTEGER HOW TO#
I'll take it as a little exercise in how to program a data reader.
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