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[GRASS-windows] (no subject)

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Nerdnum

[GRASS-windows] (no subject)

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Some javascript/style in this post has been disabled (why?)

I am trying to import the DTM files I found in the following location.

http://www.computamaps.com/en/catalog/index_2.html

The details given for the files are stipulated as follows.

Format: Planet 2.8 ®, ArcInfo Grid
Projection: UTM
Ellipsoid: WGS84
Resolution: DTM and Clutter 250m, Orthoimage and Map 125m

I am able to import the DTM files if I override the projection check, but then of course patching files together becomes a bit difficult. Is there maybe an easy way out of this?

Louis Becker
Planning Manager
Cell One
Mobile: +264 (85) 551 0136

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Moritz Lennert

Re: [GRASS-windows] (no subject)

Reply Threaded

On 01/10/08 16:48, Louis Becker wrote:

> Hi
>
> I am trying to import the DTM files I found in the following location.
>
> http://www.computamaps.com/en/catalog/index_2.html
>
> The details given for the files are stipulated as follows.
>
> Format: Planet 2.8 ®, ArcInfo Grid
> Projection: UTM
> Ellipsoid: WGS84
> Resolution: DTM and Clutter 250m, Orthoimage and Map 125m
>
> I am able to import the DTM files if I override the projection check,
> but then of course patching files together becomes a bit difficult. Is
> there maybe an easy way out of this?

What is the projection of the location you import the files into ?

Moritz
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Nerdnum

RE: [GRASS-windows] (no subject)

Reply Threaded

Hi

I have downloaded a number of file sets, but the first two I used are
called 33J and 33K, where number 33 indicates the UTM Zone 33 and J is a
tile of that with bottom left corner 32S 12E and top right corner 24S
18E (8 x 6). 33K is the tile just north of 33J.

A file set from this site comes with the following folders and (files):

Clutter - (dt, dt.hdr, index and menu)
Dtm - (dtm, dtm.hdr, index and projection)
Map - Geotif files (.TAB, .tfw, .tif and index)
Ortho - (.TAB, .tfw, .tif and index)

I am only able to define a location from a Georeferenced file if I use
the DTM file under DTM (let's call it DtmLocation). If I then display
the region settings, I get the following for DTM 33J:

projection: 0 (x,y)
zone: 0
north: 7345125
south: 6453125
west: 192375
east: 807375
nsres: 250
ewres: 250
rows: 3568
cols: 2460
cells: 8777280

If I use the tif file from the Map folder to create a location (let's
call it UTMLocation), I get the following if I display the region
settings for 33J:

projection: 1 (UTM)
zone: -33
datum: wgs84
ellipsoid: wgs84
north: 7345000
south: 6453000
west: 192500
east: 807500
nsres: 125
ewres: 125
rows: 7136
cols: 4920
cells: 35109120

If is not an issue to import the dtm file into the 33J_DtmLocation, but
is not properly referenced for further use. If I want to import the dtm
into the 33J_UTMLocation, I have to override the projection check.

Defining a location for 33K DTM yields:

projection: 0 (x,y)
zone: 0
north: 8231125
south: 7340125
west: 176375
east: 823375
nsres: 250
ewres: 250
rows: 3564
cols: 2588
cells: 9223632

Defining a location (called 33 of 33K_UtmLocation) Tif yields:

projection: 1 (UTM)
zone: -33
datum: wgs84
ellipsoid: wgs84
north: 8231000
south: 7340000
west: 176500
east: 823500
nsres: 125
ewres: 125
rows: 7128
cols: 5176
cells: 36894528

I am able to import the 33K_Dtm into the 33K_UtmLocation by overriding
the projection check. If in now try to re-project using r.proj for the
raster file in 33J_UtmLocation into the 33K_UtmLocation, then it just
does not seem to work. I also check the flag "Do not perform region
cropping optimization", but is still only import only a small "slice" of
the adjacent tile.

I have tried importing the DTM using r.in.arc, but it cannot read the
projection files, etc.

How can I do this?

Louis

-----Original Message-----
From: Moritz Lennert [mailto:[hidden email]]
Sent: 01 October 2008 22:40
To: Louis Becker
Cc: [hidden email]
Subject: Re: [GRASS-windows] (no subject)

On 01/10/08 16:48, Louis Becker wrote:

> Hi
>
> I am trying to import the DTM files I found in the following location.
>
> http://www.computamaps.com/en/catalog/index_2.html
>
> The details given for the files are stipulated as follows.
>
> Format: Planet 2.8 (r), ArcInfo Grid
> Projection: UTM
> Ellipsoid: WGS84
> Resolution: DTM and Clutter 250m, Orthoimage and Map 125m
>
> I am able to import the DTM files if I override the projection check,
> but then of course patching files together becomes a bit difficult. Is

> there maybe an easy way out of this?

What is the projection of the location you import the files into ?

Moritz
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Moritz Lennert

Re: [GRASS-windows] (no subject)

Reply Threaded

On 02/10/08 16:48, Louis Becker wrote:

> Hi
>
> I have downloaded a number of file sets, but the first two I used are
> called 33J and 33K, where number 33 indicates the UTM Zone 33 and J is a
> tile of that with bottom left corner 32S 12E and top right corner 24S
> 18E (8 x 6). 33K is the tile just north of 33J.
>
> A file set from this site comes with the following folders and (files):
>
> Clutter - (dt, dt.hdr, index and menu)
> Dtm - (dtm, dtm.hdr, index and projection)
> Map - Geotif files (.TAB, .tfw, .tif and index)
> Ortho - (.TAB, .tfw, .tif and index)
>
> I am only able to define a location from a Georeferenced file if I use
> the DTM file under DTM (let's call it DtmLocation). If I then display
> the region settings, I get the following for DTM 33J:
>
> projection: 0 (x,y)
> zone: 0
> north: 7345125
> south: 6453125
> west: 192375
> east: 807375
> nsres: 250
> ewres: 250
> rows: 3568
> cols: 2460
> cells: 8777280

This is not UTM (projection: 0 (x,y)), so it means that the projection
info in the file is not recognized. However, the extents seem reasonable.

BTW, for precise projection info about a location, use g.proj -p.

>
> If I use the tif file from the Map folder to create a location (let's
> call it UTMLocation), I get the following if I display the region
> settings for 33J:
>
> projection: 1 (UTM)
> zone: -33
> datum: wgs84
> ellipsoid: wgs84
> north: 7345000
> south: 6453000
> west: 192500
> east: 807500
> nsres: 125
> ewres: 125
> rows: 7136
> cols: 4920
> cells: 35109120

This seems right for a 33S.

>
> If is not an issue to import the dtm file into the 33J_DtmLocation, but
> is not properly referenced for further use.

What makes you say that ?

> If I want to import the dtm
> into the 33J_UTMLocation, I have to override the projection check.

Logical, since, as stated above, GRASS does not recognize the projection
info in your file.

>
> Defining a location for 33K DTM yields:
>
[...]
>
> Defining a location (called 33 of 33K_UtmLocation) Tif yields:

[...]

Same as above, so rather encourageing (as expected, you are in the same
UTM zone).

>
> I am able to import the 33K_Dtm into the 33K_UtmLocation by overriding
> the projection check. If in now try to re-project using r.proj for the
> raster file in 33J_UtmLocation into the 33K_UtmLocation, then it just
> does not seem to work.

You do not need to reproject. Both location seem have exactly the same
projection (which they should).

So:

1) Create a location with your tif (or using the relevant EPSG code -
see http://www.epsg-registry.org/).
2) Import all your DTMs into this location, overriding the projection
check and using the -e flag to extend default location extents.
3) If you need to combine all files into one, use r.patch.

Moritz
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