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Loading DEM files

 
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John Pickerill



Joined: 03 Nov 2005
Posts: 3

Tasmania, Australia

PostPosted: Tue 11 Apr, 2017 4:52 pm    Post subject: Loading DEM files Reply with quote

I am trying to input a .DEM file from a surveyor but get an error message "cell size not defined". There no option to set cell size. Any suggestions.
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Matthew Monk



Joined: 21 Oct 2005
Posts: 1813

Victoria, Australia

PostPosted: Tue 11 Apr, 2017 5:29 pm    Post subject: Reply with quote

Assuming (Rolling Eyes) you're expecting an ArcInfo DEM format, the cell size is meant to be set inside the file itself. Something like this:
Code:
ncols         4
nrows         6
xllcorner     0.0
yllcorner     0.0
cellsize      50.0
NODATA_value  -9999
-9999 -9999 5 2
-9999 20 100 36
3 8 35 10
32 42 50 6
88 75 27 9
13 5 1 -9999
If you open your DEM in a text editor, does the top of the file look like that? Is it definitely an ArcInfo DEM format (also called an ESRI ASCII Grid) or does it just happen to have a .dem extension? Do you know the cell size?
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Lee Gregory
12d Support


Joined: 29 Sep 2005
Posts: 1487

PostPosted: Tue 11 Apr, 2017 7:39 pm    Post subject: Reply with quote

Can you ask the Surveyor what the format is for the .DEM file you were given.

Unfortunately many software packages have used .DEM and the files are not related at all.

If you look at the beginning of the file as Matt suggested, you may find it is just an xyz file.
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John Pickerill



Joined: 03 Nov 2005
Posts: 3

Tasmania, Australia

PostPosted: Wed 12 Apr, 2017 11:57 am    Post subject: Loading DEM files Reply with quote

The top of the file in Notepad looks like shown below. I believe it may be an xyz file. Problem being it is from a LIDAR survey and is huge, exceeds 5M points. The surveyor does not seem to be able to make it smaller. Will keep trying.

Thanks.
"
0 1 1 9 0 0.000000000000000 0.000000000000000 0.999600000000000 0.000000000000000147000000.00000000000000 0.000000000000000 500000.00000000000000010000000.000000000000000 0.000000000000000 0.000000000000000 0.000000000000000 0.000000000000000 0.000000000000000 0.000000000000000 0.000000000000000 2 2 4 633786.722957008400000 7517347.050566205800000 633786.722957008400000 7551197.050566205800000 669131.722957008400000 7551197.050566205800000 669131.722957008400000 7517347.050566205800000 142.000000000000000 219.000000000000000 0.000000000000000 0 5.000000 5.000000 1.000000 1 7070 00 00 0 0 0 0 0-1 0 0 0 0 0 00.00 1 1 3564 1 633786.722957008400000 7533382.050566205800000 0.000000000000000 179.367355346679690 218.892089843750000 208 207 207 "
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Lee Gregory
12d Support


Joined: 29 Sep 2005
Posts: 1487

PostPosted: Wed 12 Apr, 2017 1:54 pm    Post subject: Reply with quote

It certainly doesn't look like an ArcInfo DEM format so you need to find out from the Surveyor exactly what the DEM format is.
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