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Variable width corridor for path profile?

jopacakjopacak Posts: 3
in Elevation Data
Hello everyone, I have been using Path Profile tool for a while. The option to create an elevation corridor and 'keep maximum elevation along perpendicular' is very useful. However, now I'm looking into creating "variable width corridors" (rather than rectangular) for the path profile to be shown.
Attached is an example showing a black solid line along which I need to evaluate maximum elevation, but only to the extents of the yellow variable shape.
Is there any option or workaround to do this?
Thank you!

Answers

  • CarrickConCarrickCon Posts: 57
    Hi Jopacak. Wow, tricky question!

    As you have probably already noticed the "Distance from Path" under the Path Profile Settings menu is fixed and will only allow sampling at a fixed offset either side of your central corridor.

    If I had to do what you are asking (and I hope I never do! <span>:smile:</span>) I think I'd do it iteratively by increasing the length of the Perpendicular Profile as you move along the central corridor (in your case from SW to NE). I'd then view each cross-section and right click on "Show Path Profile Details" to see "Maximum Elevation on Path" and copy to clipboard if required or if I needed x,y,z of highest point I'd right click and select File/Save CSV File  and then bring into Excel say and pick maximum elevation point using @Max command.

    Its a bit of pig of a thing to have to do, but that is what I'd do as a workaround. I've attached a few screen grabs of an example. Hope this helps.

    Ta,
    /al
    sphillips
  • jopacakjopacak Posts: 3
    Hi CarrickCon, thanks for taking the time to answer and try it on your own GM. This kind of stuff is very common when evaluating terrain corridors near an airport.
    I see your point and it might be worth a try. However, as you said, it looks like tons of iterations in order to have a reasonable precision. :#
    I will give it a try and see how it goes.
    Thank you!

  • CarrickConCarrickCon Posts: 57
    Hi Jo, perhaps a simpler way to go would be to crop your terrain to the trapezoidal shape in question and then use contour max/min tool to show highest point within shape? Alternatively you could use the show water level tool to highlight highest point(s). Might be simpler. I've attached a few screen shots...

    (Screen shot #1 shows terrain, #2 cropped to shape and then #3 with high/low spots using contouring tool.  #4 is with the "Shows water " tool turned on - I use this tool a lot! for flood inundation studies).

    Cheers,
    /al



    sphillipsjopacak
  • 946946 Global Mapper User Posts: 156Trusted User
    Why not creating a surface from your trapezoid shape and extract the Terrain underneath?
    Assuming your polygon is a 3D height evaluation  surface of course.



    sphillipsjopacak
  • jopacakjopacak Posts: 3
    Dear CarrickCon and 946,
    Thanks for taking the time to see this and your feedback. Based on your both answers, I was able to find a workaround to this. I'm very grateful for your support.
    As suggested by you, I cropped the digital elevations layer to the trapezoidal area selected (layer OPTIONS > FEATHERING > Feather within currently selected polygon).
    Then, using my previously defined horizontal path, I get the path profile checking the option to "keep the maximum elevation along perpendicular", and the distance from path set to the longest width of the corridor. Given the fact that any point outside the polygon will now have zero elevation, the maximum elevation displayed belongs to the cropped area only, thus the problem is solved! Of course I could use an even greater length for the perpendicular distance, still with the same results...


    You can check all this is working ok by using the option to "extract lines/areas from perpendicular profiles", inside the path profile window.

    :)
    /JM
    a.JPG 55.6K
    b.JPG 65K
    c.jpg 209.6K
  • CarrickConCarrickCon Posts: 57
    Nice one JM! That's the beauty of Global Mapper - even if there isn't a pre-built tool for doing something, there is nearly always a workaround...

    Cheers,
    /al 
    jopacak
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