[FWTools] Support for SRTM data

[Quentin Scouflaire]

Frank Warmerdam wrote:

>On 4/19/05, Robert Uzgalis <buz at zis.com> wrote:
>  
>
>>I just installed fwtools (on a winnt system) and tried displaying some
>>SRTM-1 data and then realized that there seemed to be no support of SRTM
>>data at all.  Am I missing something simple?  Or is it just not there.
>>    
>>
>
>Buz, 
>
>SRTM is a data product.  What format is it distributed in?  I have most
>often seen it distributed as raw binaries files with a particular naming
>conventions, and in some cases associated ascii header files (.ers
>in one case I have noticed). 
>
>GDAL doesn't have any specific support for the SRTM naming
>convention and only supports the raw files if they have a supported
>header format (the ers files don't work as I recall).   
>
>Best regards,
>  
>
The "official" documentation for the SRTM Topo data (.HGT format) is here :
ftp://e0mss21u.ecs.nasa.gov/srtm/Documentation/SRTM_Topo.txt

All files are basically referenced thanks to their name - and that's how 
most GIS software deal with such data.
Naming convention: N60E173.hgt for a 1x1 degree tile covering N60 to N61 
and E173 to E174, in WGS84 datum. S11W153 for a 1x1 degree tile... S11 
to S10, W153 to W152. No matter their internal point spacing, all tiles 
cover one square degree.
Wouldn't four implicit GCPs be sufficient for basic support in gdal ?
(IMHO the other ways involving various header files must be intended 
with GIS compatibility in mind and/or greater security in case of file 
renaming.)

Greetings,