No Luv For MicroDEM v4 ?

[DrFrag]

Hello, is there any particular reason TranzDEM doesn't support MicroDEM version 4 files?

I stitched together 14 tiles in TranzDEM and then opened the DEM file in MicroDEM to edit the header data and after saving it out I can no longer open it in TranzDEM. It appears to be a MicroDEM version 4 file now and accourding to the manual TranzDEM only supports v1, 2, & 3.

Is there a way to get this file back into TranzDEM or is it possible to edit header data with TranzDEM?

The purpose is to compress the terrain horizontally (not resample) to make more interesting terrain for my fictitious branch line. I'm not even sure if changing the X & Y values in the header will really do what I want as I'm not sure if the grid values are just elevations or include location data as well.

Thanks in advance for any advice,
David

[DrFrag]

D'oH

I opened it back up in MicroDEM and found the Save DEM options so I chose USGS ASCII. Not sure if that's the best option but TranzDEM seems to be okay with it.

David

[geophil]

David,

where did you get the information about a new MicroDEM .dem format version 4? I checked the latest MicroDEM documentation this morning but could not find any additions or changes there.

TransDEM has a few restrictions for the MicroDEM .dem format. The projection must be UTM, datum WGS84, NAD83 or equivalent and elevations have to be in metres. "USGS ASCII" is the old text .dem file, I think, still in use by the Canadians and now also by the Norwegians. For TransDEM this format was restricted to WGS84/NAD83 Plate Carrée pseudo projection (units in arc sec), but was extended to UTM and metres for Norway with TransDEM 2.5.1.

Fiddling with the DEM geo referencing information in TransDEM is not really supported. There is a function in TransDEM for something like this, called "Shift DEM", but it's limited to 1000 m per invocation and intended to fix georef errors.

[DrFrag]

Here's the header for a file I saved out of MicroDEM after changing the X & Y to 2 meters.
Here's a link to the file: http://drfrag.net/N40-41W119-125_cropped-2m-v4.7z

*MICRODEMv4
numcol=20203
numrow=4135
maxz=4000
minz=-10
dx=2
dy=2
llx=401124.34375
lly=4500660.5
utmzone=10
projtype=0
precision=1
spaceunit=0
elevunit=0
digdatum=1
fipszone=0
hemi=N
h_datum=WGS84
*END

[geophil]

Thank you. Meanwhile I have found the small print in the MicroDEM help file. It has a very short note on the new format and the changes appear to affect the header only. The header structure in the older versions was quite Delphi-oriented, the programming language MicroDEM is written in. The new tagged value style is much more straightforward. It has also abandoned many rather obscure header elements which TransDEM often ignored. The tag names look like the former Delphi structure variable names, so that might be a clue to interpret them. I should already have a class for reading line oriented tagged values in my libraries, as TransDEM uses the same format for non-xml text files.
Anyway, a note has been added to my todo list.

[DrFrag]

Excellent, sounds like progress.

I'd hate to see your ToDo list.