DEM Tutorials

[geoskimoto]

Hi Everyone,

I'm new to this group and new to Model Muse.  After the past few weeks I've been picking up Model Muse pretty quickly thanks to Hatari Lab's awesome tutorials.  That being said, one thing that is driving me absolutely nuts is importing DEM's.  Can anyone give me a complete breakdown on how to import a DEM into Model Muse and maybe formats of DEM's in general?  

I have downloaded ASTER DEM's from NASA's earth data tool, DEM's from USGS's National Map, and even have LiDAR of the area I'm trying to model.  What do I need to do to get these to import into Model Muse?  With these files, I am able to load them into QGIS.  In QGIS, I translate them into every format I can think of (surfer grid, ASCII .asc, STDS), but nothing seems to work.   In Model Muse, I only get the error "X File is not a Surfer grid/ASCII raster file" when I try to import them.  Do I need to interpolate the DEM files before I convert and import them?

Thanks for any tips!

[César Rodriguez]

You need to have a grid already set up when you import the DEM (At least with ASCII rasters, those are the ones I use). Then, when you import it, it will allow you to choose an interpolation, and what data set you want the information to land on (either a new data set or model_top usually).

If it's telling you that whatever you're importing isn't a raster (or a surfer grid), check if you have different encoding options when you export in QGIS (I've never had this problem, so this is just a guess). It's weird it's telling you that with ascii rasters though, it's a pretty simple file format.

Good luck with your DEMs!

[geoskimoto]

Yeah, I'm still having issues importing any and all DEM's.  My work around currently is using the LAS2txt tool in LAStools in QGIS to extract point data from the LiDAR data that I have and then importing points into Model Muse.  I think it's working.  This is incredibly frustrating though because I've literally have spent 4 days now trying to everything that I can think of to get a different DEM's to import without any success.  

Can anyone just explain their process of importing a DEM?  From where they download it from, to any alterations or conversions you may do to it in GIS, to how they import it into Model Muse?  

Thanks

[César Rodriguez]

Ok, so you're using las2txt. Do you know what actual format that txt is in? I don't know about QGIS, but in arcGIS, after extracting lidar data as a multipoint feature, the next step would be transforming those features into a raster (cause Lidar data doesn't necessarily contain equally spaced points), and then exporting that to Ascii raster file. Then to import, you just hit import, ascii raster file and set the values in the raster to be Model_Top. It's important that you have your grid already where the raster is going to "land" on the model, so the importing process assigns a value to the Model_Top in each cell. If you try importing without a grid, ModelMuse won't have cells to assign the values to.

I know it's pretty much the same thing I wrote in my past answer, but I don't know what can be going wrong.

Also, check out this video: https://www.youtube.com/watch?v=VHt8dXbLwo4

At around 16 minutes in, he starts importing a raster file, and talks a bit about the process. Hope it helps. Good luck!

[Nadège et Didier Vanden Berghe]

Forgive me if my reply doesn't feet exactly your demand, but it seems to me that you can import a point shapefile in MM, and then interpolate your dem directly in MM from this dataset. Saying differently : you may import your DEM in SAGA (the very nice geostatisctical software delivered together with QGIS), export it in a point shapefile thanks to the appropriate SAGA tool, and finally import and interpolate it in MM. This may cost you a bit of model space and time for the interpolation, especially if your initial dataset is huge.

[geoskimoto]

Realized I never responded to these responses.  Wanted to let everyone that I found a work around.  I imported several hundred xyz points and interpolated them to the model surface top. Can't remember exactly what I used, but in QGIS I used some plugin that allowed me to extract points from a DEM by just clicking several hundred times.  I still have no idea why I can't just simply import a DEM into Modelmuse.