POV-Ray : Newsgroups : povray.pov4.discussion.general : Request *.dem and *.hgt format : Re: Request *.dem and *.hgt format Server Time
25 Sep 2023 01:28:05 EDT (-0400)
  Re: Request *.dem and *.hgt format  
From: Nekar Xenos
Date: 18 Jan 2011 02:37:12
Message: <op.vpht38xvufxv4h@xena>
On Tue, 18 Jan 2011 09:10:15 +0200, clipka <ano### [at] anonymousorg> wrote:

> Am 17.01.2011 20:52, schrieb Nekar Xenos:
>> "Height files have the extension .HGT and are signed two byte integers.
>> The
>> bytes are in Motorola "big-endian" order with the most significant byte
>> first,
>> directly readable by systems such as Sun SPARC, Silicon Graphics and
>> Macintosh.
>> DEC Alpha and most PCs use Intel ("little-endian") order so some
>> byte-swapping
>> may be necessary. Heights are in meters referenced to the WGS84 geoid.
>> Data
>> voids are assigned the value -32768."
> That's pretty meager; some information would be needed about the number  
> of columns & rows, and how this format deals with the spheroid shape of  
> earth.

 from http://www2.jpl.nasa.gov/srtm/faq.html :

"The SRTM data files have names like "N34W119.hgt". What do the letters  
and numbers refer to, and what is ".hgt" format?

Each data file covers a one-degree-of-latitude by one-degree-of-longitude  
block of Earth's surface. The first seven characters indicate the  
southwest corner of the block, with N, S, E, and W referring to north,  
south, east, and west. Thus, the "N34W119.hgt" file covers latitudes 34 to  
35 North and longitudes 118-119 West (this file includes downtown Los  
Angeles, California). The filename extension ".hgt" simply stands for the  
word "height", meaning elevation. It is NOT a format type. These files are  
in "raw" format (no headers and not compressed), 16-bit signed integers,  
elevation measured in meters above sea level, in a "geographic" (latitude  
and longitude array) projection, with data voids indicated by -32768.  
International 3-arc-second files have 1201 columns and 1201 rows of data,  
with a total filesize of 2,884,802 bytes ( = 1201 x 1201 x 2). United  
States 1-arc-second files have 3601 columns and 3601 rows of data, with a  
total filesize of 25,934,402 bytes ( = 3601 x 3601 x 2). For more  
information read the text file "SRTM_Topo.txt" at  

-Nekar Xenos-

"The spoon is not real"

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