Instability with watershed generation

sktsesktse Global Mapper UserPosts: 31Trusted User
edited July 2013 in Technical Support
Hi guys,

I've been trying to generate a watershed model with a high-resolution DEM over a highway. Unfortunately, I've been having some problems with the program hanging, crashing or just generally taking a very long time.

1) When I try to map watersheds in a very large area, the program will take a very long time to generate. Now, this is understandable, but the time estimation is very unreliable so it always tells me that it will be done generating the watersheds the next minute, but it shows this same text for the next 4 hours. Would there be a way somehow to give a rough but accurate estimate of the time needed to generate the watershed file so that I can cancel the process and re-adjust my parameters?

2) My highway is digitized as a series of line features. I thought it might be a good idea to try selecting the line feature, and then try generating all the watersheds that lead to the line (i.e. delineate all the watersheds that are upstream of the highway). When the program ran, it generated all the way until it got to the 100% mark and then froze, which meant I had to close the program. Am I using this feature improperly?

3) I'm wondering if it's possible to include an audible sound that plays when processing that takes a great deal of time has finally completed. When the program is creating output, I like to move and work to other projects while the program does its thing. Then if I have an audible alert, I can immediately return to global mapper without missing a beat.

Thanks for this wonderful program, it really has helped me a lot!

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2013
    How large of an area are you trying to generate the watershed for and what sample spacing are you using? You could try increasing the sample spacing (i.e. decreasing the resolution) a bit which can dramatically speed things up, especially if you don't need the full resolution that the DEM might provide. This is often the case for Lidar-derived data.

    When the program locks up at 100%, what does the status say on the progress dialog? I think it's probably just finding the drainage to the lines and typically that operation is quick enough that it doesn't add anything to the progress, but in some very large cases or with lots of roads this could take a while with no way to cancel. If that's the case I can see about adding some useful progress for that.

    I did update the progress reporting so that if an operation takes more than 5 minutes to complete you will get a sound played at the end, so long as you have Windows sounds turned on. I have placed a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v14.xx installation folder to give it a try. If you are using the 64-bit v14 version there is a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper14_64bit.zip .

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • sktsesktse Global Mapper User Posts: 31Trusted User
    edited July 2013
    Thanks for the quick reply!

    The watersheds I've calculated so far range from 0.4 - 50 hectares, and my sample spacing is approximately 0.37 m. You're right that LiDAR data is being user, and so I've tried your suggestion and raised the sample spacing to 1m.

    I will give your new build a try, thank you very much!
  • sktsesktse Global Mapper User Posts: 31Trusted User
    edited July 2013
    Okay, so I tried generating a watershed with just the streamlines because I had generated a basin previously and the streams did not have enough detail. The settings I used were:

    - Stream Cell Count: 50
    [X] Discard Stream Starts Less than 50 m in Length
    Resolution: X-axis: 1, Y-axis: 1
    [X] Interpolate to Fill Small Gaps in Data
    [X] Smooth Streams to Improve Appearance
    [X] Keep Ocean Elevations (i.e. 0 meters) at Zero
    Depression Fill Depth 15 meters

    Everything else was left unchecked.
    For the watershed bounds tab, I selected a polygon and asked the program to use that selected feature as the bounds.


    Error calculating water shed.
    Read access violation at data address 0x00000010,
    program address 0x00928914.

    Version: v14.2.1
    Build Time: May 28 2013 18:31:50
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited July 2013
    Can you first download and install v14.2.3 from Global Mapper Downloads and see if it generates the same error? There were several bugs in v14.2.1 that have been fixed. If that still fails then I can try and replicate the issue.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
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