Modify and exaggerate the vertical height shown in a DEM processed using WebODM
I am using the latest software that allows WebODM to run on a Windows computer running Windows 10 OS without using Docker. When I generate a Digital Elevation Model, or Ground Elevation Model, I want to map large flat areas without trees or buildings to show depressions in the ground with exaggerated elevation relief. In other words, a small hole in the ground becomes a deeper and wider hole in the fabric of the elevation plane. I also would like to be able to exaggerate the elevation of small vertical features on the surface of the ground.
Is there a setting in WebODM that does this? What are the steps that I must use to to achieve my goal?
Thanks
Geneo24
I actually have QGIS on my computer, but I have not ever successfully used it so I am not sure if it still works properly. I was reading OPEN DRONEMAP The missing Guide and came across SMRF-Threshold on page 99. It seems that by setting this value, the surface model features might be exaggerated so that small depressions or vertical features show up in more detail.
What would be the steps to use QGIS for my need?
Geneo
Yep, there are a number of smrf parameters that one can tune, but I’m still exploring/testing what that looks like, so I can’t give good guidance on that at present, unfortunately.
As for a general flow in QGIS, this should get you started:
Raster Calculator, and use a scaling value by multiplying the raster band by a number.
Saijin:
It would be advantageous to stay in WebODM if at all possible, but using QGIS is not out of the question. The learning curve on QGIS seems rather steep. My version does open and I did find Raster Calculator, but how to use it is another question.
Please tell me how one would go about changing the SMRF parameters in WebODM, specifically the SMRF-Threshold value. Keep in mind that I am using the Windows OS version of WebODM without Docker.
Also, how is the best way to get the raster output of WebODM and save it so that it can be imported into WGIS?
Thanks
Geneo
SMRF Tuning:
As before, I’m not the most educated in this area yet, and I’m still experimenting with the various parameters and how they react so that I can put that into our documentation.
You could do something like RASTERNAME * 1.5 to create a 1.5x vertical scaling factor, but it will affect both positive and negative features equally. So, you might need to use the Reclassify tool to separate out “bins” of elevation ranges you want to modify, run the Raster Calculator against them separately, then merge them all again into a compisite…
If you like to learn gis there’s a great course at Coursera. It’s on ArcGis but it’s very similar and you can use what you learn in QGis. I took it and doesn’t regret it one bit even though I don’t use it that much.
“Geographic Information Systems (GIS) | University of California, David”
Andreas: Thanks for the pointer to the GIS Course. Yes, I need to take the course and I am investigating it thanks to your very timely tip.
Thank you very much for your time.
Smathermather: Thank you very much for the advice. Unfortunately, I am not smart enough to use the information as provided.
Where does the adjustment knob live and how do I get there when my WebODM project is open and I am in either 3D or 2D (not sure which one to be in) I opened FILTERS while in 2D but the window and knob are not there.
Saijin: Thank you very much for including the example of how to go in and set SMRF parameters and of course other parameters. A picture is worth a thousand words.
I went in and changed the smrf-threshold from 0.5 to 0.2 and ran a group of images. Then I ran another group of images at a modified threshold of 0.9.
I don’t see much difference in the 2D output image when looking at the 0.9 threshold setting after change from default 0.5… When I set the threshold to 0.2 not much difference from the default value of 0.5.
Can you tell me which of the output products produced by WebODM are those that the changes in smrf-threshold is supposed to show up in? I apparently am not selecting the right product to see the changes when I adjust the threshold value.
As always, thank for the help.
Gene024
Thank you for that information. I plan to work with the SMRF-Window function on Thursday. What WebODM product does the change in Window function show up?
You should see the results in the DEM and related products, so DTM, and DSM. These you’ll see in the top of your Map View if you’ve enabled them for export in your Processing Parameters as Surface Model and Terrain Model.
My reading of that is that it is a filter for determining ground and non-ground points, it can’t do the vertical exaggeration you are looking for.
Have you tried loading the output ortho into Google Earth as an overlay, and then setting vertical exaggeration to more than 1? It allows up to 3X vertical scaling, which does make some landscapes look pretty amazing!
