Global Mapper v25.0

Elevations on initial section of profile reverting to zero

currang2
currang2 Global Mapper UserTrusted User
edited January 2011 in Technical Support
I have been trying to obtain a river profile from SRTM data using the 3D profile tool. However, when I get to the end of the profile I find that a number of the first points have been given zero elevations.

The river is fairly long at 150km.

The number of points set to zero does not seem to be a constant.

Is this a bug? Is there something I have to set to ensure that all elevations are retained?

Comments

  • global_mapper
    global_mapper Administrator
    edited December 2010
    Which version of Global Mapper are you using? There was recently an issue with the path profile sampling with some sampling options. If you have v12 the latest build should work fine though. I have placed a new build at http://www.globalmapper.com/global_mapper12.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v12.xx installation folder to give it a try. If you are using the 64-bit v12 version there is a new build at http://www.globalmapper.com/global_mapper12_64bit.zip .

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • currang2
    currang2 Global Mapper User Trusted User
    edited December 2010
    I was using the 3D path profile line of sight tool.

    Hovering over the map I can see the elevations.

    Clicking on just a few points I get a track with valid elevations.

    If I just set off upstream, by the time I get to the end and view the profile, the first buch of points all have zero elevations and there is an abrupt jump in the porfile somewherer upstream where the elevations kick in.

    I will try the newer build to see if that helps. I was using V12.00
  • currang2
    currang2 Global Mapper User Trusted User
    edited December 2010
    V12.0

    The new build didn't help.

    I can't identify a particular point in the map where the jump occurs, nor is there a definite number of points, beyond which the problem happens.
  • global_mapper
    global_mapper Administrator
    edited December 2010
    Can you post a screenshot of what you are seeing? Are you basically clicking a lot of points to define your path in the 3D path profile tool and seeing the first several of those as 0? If you create a line first for your path in the Digitizer Tool, then select it and right-click and select the option to show a 3D path profile do you have the same issue?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • currang2
    currang2 Global Mapper User Trusted User
    edited December 2010
    I'll post screenshot tonight when back in range of internet connection.

    Yep, your description of seeing the first several points as zero is correct.

    I'll try the digitised line option then as well. I haven't yet woorked out how to bind the 3D data into a project file so that I can access the data when I am off-line. Is there a way?
  • global_mapper
    global_mapper Administrator
    edited December 2010
    If you export the data to a new file (use File->Export Elevation Data) then you can load that data from the file rather than using the online source so it will be available offline.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • currang2
    currang2 Global Mapper User Trusted User
    edited December 2010
    3d line.jpg
    I think image from 3D profile tool is attached. Shows first half of line all zer elev.
    Digitiser tool works sometimes, but I cant right click and elect to see profile.
    When I try to update elevations from terrain from inside the vertices dialog I get the message "There was not terrain data for the entire feature" and no elevations get added. That sounds like there are gaps in the SRTM terrain data (that I had previously heard about). Could that be the problem?
  • global_mapper
    global_mapper Administrator
    edited December 2010
    I agree I think the issue has to do with an online source like SRTM going off the screen as you pan around. I will have to look at that. In the meantime if you first export to a file and load that then you should be fine.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • currang2
    currang2 Global Mapper User Trusted User
    edited January 2011
    I finally got back to the problem.

    I couldn't download the terrain data to a file I could subsequently load. I thought that was how it would be done.

    I did export the catchment and terrain to a global mapper package file and was able to then open that file and set the vertices of the digitised line.

    Now I will try creating a 3D line directly.
  • currang2
    currang2 Global Mapper User Trusted User
    edited January 2011
    Tried using the 3D path with the global mapper package file. Works fine. No zero elevations.

    It looks like there is some sort of bug that causes the elevations to drop off the back end of the 3D path, and to prevent the digitiser tool setting elevations from the on-line elevation data.

    Thanks for your help. Sorry I took so long getting back to the question.
  • currang2
    currang2 Global Mapper User Trusted User
    edited January 2011
    I followed up by using the 3D path tool on the exported global mapper package file. It worked without a hitch and I didn't have any drop out of the elevations.

    So it seems that you can't reliably use either the 3D path tool or the digitised line tool on on-line data. You have to export all the data as a .gmp file and then wok on that.
  • global_mapper
    global_mapper Administrator
    edited January 2011
    I took a look and found the issue with generating a path profile from online sources when the profile goes off screen a ways. I have placed a new build at http://www.globalmapper.com/global_mapper12.zip with this fixed for you to try. Simply download that file and extract the contents into your existing v12.xx installation folder to give it a try. If you are using the 64-bit v12 version there is a new build at http://www.globalmapper.com/global_mapper12_64bit.zip .

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • currang2
    currang2 Global Mapper User Trusted User
    edited January 2011
    That new build certainly solved the problem. I can now get vertices for the digitised line, and the 3D path looks OK now.

    Plus I have learned things along the way.

    Thanks.