[GRASSLIST:4495] Re: hgt to bil (SRTM)

[William K]

Oh blast!  Just figured out that GDAL takes care of the cell center -> 
cell edge conversion of the header.  So my method shifted everything NW 
1/2 cell.  So it's even simpler: the ULXMAP is the tile longitude, and 
add 1 to the latitude for the ULYMAP.

Good thing I noticed before importing the whole US next week.  And 
that's probably why the VMAP0 coasts didn't match very well before ^_^


On Oct 7, 2004, at 12:29 PM, William K wrote:

> I had to wrestle with this and here's what I figured out.  First, the 
> cells in the SRTM are center-based, so you need to take into account 
> 1/2 the cell for the UL corner.  And there is a 1 cell overlap between 
> tiles.  So, if you have a cell as your example:
>
> 1. add 1.00041666666667 to latitude for ULYMAP
> 	12.00041666666667
> 2. subtract 0.00041666666667 from longitude for ULXMAP
> 	43.9995833333
>
> this will put the corner in the correct position 1/2 cell outside the 
> upper-left.
>
>
> On May 17, 2006, at 4:50 AM, ivan marchesini wrote:
>
>> Dear Users,
>> I'm trying to understand how to create the hdr file for the .bil srtm
>> dem I downloaded....
>> I have found too much different information... so I try with you....:
>> if I have a N11E044.hgt file I have to rename the file to  N11E044.bil
>> and then to create a N44E011.hdr file...
>> can you help me to insert the right value in the ULXMAP and ULYMAP
>> sections of the hdr file below.... ???
>>
>> BYTEORDER M
>> LAYOUT BIL
>> NROWS 1201
>> NCOLS 1201
>> NBANDS 1
>> NBITS 16
>> BANDROWBYTES 2402
>> TOTALROWBYTES 2402
>> BANDGAPBYTES 0
>> NODATA -32768
>> ULXMAP  ??????????????
>> ULYMAP  ??????????????
>> XDIM 0.000833333333333
>> YDIM 0.000833333333333
>>
>>
>> Thank you very much....
>> Ivan
>>
>>
> -----
> William Kyngesburye <kyngchaos at charter.net>
> http://webpages.charter.net/kyngchaos/
>
> All generalizations are dangerous, even this one.
>
>
-----
William Kyngesburye <kyngchaos at charter.net>
http://webpages.charter.net/kyngchaos/

"Time is an illusion - lunchtime doubly so."

- Ford Prefect