Global Mapper v25.0

Different volume results with different actions GM15

rotoview
rotoview Global Mapper UserTrusted User
edited December 2013 in Technical Support
Hello!

I just tried one of the "new" features in GM15, volume calculations of piles.
Second option from top in the right column.
I got 3923m3.
Then i tried my earlier way to calculate piles.
Adding hights to the vercities from the DEM.
Then using the digital tool to right click and use the advanced measurments tools "Cut n fill" volume.
That got me 4190m3 (0.2m3 in cut volume).

Of come it differs 267m3?

Which way is the most accurate?
pile_difference_rotoview.se.png

/Johan, www.rotoview.se | Fotogrammetri Volymberäkningar Terrängmodeller Ortofoto Flygfoto Husfoto Flygfotografering Helikopterfoto Karlstad Värmland (SWEDEN)

Comments

  • global_mapper
    global_mapper Administrator
    edited December 2013
    Johan,

    When you use the Digitizer Tool method to measure the cut-and-fill volume of the area what do you select on the Measure Volume dialog? The option to measure the volume using the terrain heights at the vertices should be what you want. That should give the same results as the measure pile volume, although it's possible the sample spacing to calculate volumes is different if you override those resulting in small differences, perhaps on the order that you are seeing.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Global Mapper
  • rotoview
    rotoview Global Mapper User Trusted User
    edited December 2013
    Hello Mike and all others :-)

    I have been using this method:
    1) use the measurementtool creating an area with vercities around the pile.
    2) Save the area
    3) Selecting the area with the "info tool".
    4) Choosing vercities, add elevations, update vercities hights from terrainmodel.
    5) Selecting the pile with the digitizer tool, rightclick calculate cut/fill volume (see attached picture)
    digitizertool_rotoview.se.png
    Suggestions are welcome.
    Wich creates the most correct volume?
    Johan
  • rotoview
    rotoview Global Mapper User Trusted User
    edited December 2013
    Im using this option "above sea level".
    digitizertool2_rotoview.se.png
  • global_mapper
    global_mapper Administrator
    edited December 2013
    In theory the 'Use Heights from Terrain Surface at Boundary' and 'Specify the Base Height to Use at Each Vertex' with the vertex heights set from the terrain should generate identical results if all else is equal. However I just found a bug in that when the area already had per-vertex elevations assigned and you used the 'Use Heights from Terrain Surface at Boundary' option. I've fixed that now so they should agree again. I have placed a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper15.zip with the latest changes for you to try. Simply download that file and extract the contents into your existing v15.xx installation folder to give it a try. If you are using the 64-bit v15 version there is a new build at http://www.bluemarblegeo.com/downloads/global-mapper/global_mapper15_64bit.zip .

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • rotoview
    rotoview Global Mapper User Trusted User
    edited December 2013
    Hello!
    Now it works. Got same volume with both ways to calculate.
    Does this mean that i have to back check all earlier projects and re-calculate for correct volume?
    Wich way of doing it gave the correct data before?

    Johan
  • global_mapper
    global_mapper Administrator
    edited December 2013
    Johan,

    If you had already assigned per-vertex elevations to the areas then the only way that would have given correct results before was the bottom option on the Measure Volume dialog where you specified the height of each vertex above sea level. If your areas didn't have per-vertex elevations already then the normal Pile Volume should have worked before too, but it might be a good idea to spot check some older ones since there are so many variables here. I apologize for any trouble.

    Thanks,

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