Creating a smooth flatten area

dbadba Global Mapper UserPosts: 2
edited October 2013 in Elevation Data
hi all,

I'm a flightsim developer and I often use DEM data to create elevation models. In flightsim runways are always flat, so whith sloped terrain there's always a problem at the beginning or end of the runway, a platform appears sometimes very important !

it's possible to use 3D polygons to fill and smooth the missing terrain, but it's very difficult and long to do it. A better solution should be to edit the elevation data all around the runway so that the terrain comes very smoothly to its natural elevation about 1km far. I saw a flatten function in GM9 but I don't know if there's an automatic elevation smoothing all around it ?

could somebody help me ?

thank you for this wonderfull GM9 software :-)

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2007
    You could use the feather blending option for elevation layers in GM9 to do what you want. First load your underlying terrain layer, then create a terrain layer that is flat with the elevation for the entire layer set to the runway elevation. Then, use the Digitizer Tool to draw an area feature that is parallel to the runway, but expanded out to your maximum desired blend distance. Then, select that area, open the Overlay Control Center, select the runway terrain layer, press Options, then go to the Feathering tab and select to feather to the selected polygon and press Apply to see the blending effect. You'll want to mess with the blend pixel range to get the desired blending effect to go to the edge of the runway (or you could create another layer with just the runway flattened out on top of the feather-blended layer).

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • joeysiposjoeysipos Global Mapper User Posts: 1
    edited May 2008
    Mike,
    You said: "create a terrain layer that is flat with the elevation for the entire layer set to the runway elevation."

    My question is how do you create flat terrain layer at a given elevation?

    And I got another question as well. Say I just wanted to flatten out a section of terrain like this guy want to do. Is this the easiest way to do that? Is there a way to export the elevation as a tiff then some how edit the tiff file with a photo editing program to flatten and take out artifacts? Then put it back into GM and create elevation data with the edited image? Is there an option some where in GM to create elevation values for the color pixels on screen? In general, If you were me, how would you go about flattening and editing the terrain?

    Thanks so much for your help Mike:)
    I greatly appreciate it! GM is awesome!

    -Joey
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2008
    Joey,

    To easily create a flattened terrain surface, just draw an area feature of the desired area and provide an ELEVATION attribute for it set to the height that you want (say '50 m' or '100 ft' or whatever). Then, select that area with the Digitizer Tool, right-click, then select the option to create flattened terrain from the selected area.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • fsdreamscapesfsdreamscapes Global Mapper User Posts: 34
    edited May 2008
    Mike thanks for the info on that, I've always wondered about that approach to solving that issue, will test it out at my end...
  • bsmavollanbsmavollan Global Mapper User Posts: 5
    edited October 2013
    You could use the feather blending option for elevation layers in GM9 to do what you want. First load your underlying terrain layer, then create a terrain layer that is flat with the elevation for the entire layer set to the runway elevation. Then, use the Digitizer Tool to draw an area feature that is parallel to the runway, but expanded out to your maximum desired blend distance. Then, select that area, open the Overlay Control Center, select the runway terrain layer, press Options, then go to the Feathering tab and select to feather to the selected polygon and press Apply to see the blending effect. You'll want to mess with the blend pixel range to get the desired blending effect to go to the edge of the runway (or you could create another layer with just the runway flattened out on top of the feather-blended layer).

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com


    Hi Mike.

    Pardon me for bringing up an ancient thread but it's the one i've been failing with :P

    Just like the OP I'm trying to feather my airport polygon into the surrounding area. My elevation data is .dem with 10m resolution. What I'm doing is:

    - Making a polygon with an elevation attribute to (in one instance 17.4m), and I choose to "create terrain". This gives me the desired flatten at the correct altitude :)

    - Next I create an polygon surrounding the first polygon but this expanded out a bit.
    (Should I give this polygon any additional attributes?)

    - I now select/highlight the second polygon, open up control center and select the elevated/flattened polygon, go
    to feather and choose to "Feather within currently selected polygon"
    (Am I doing ith right so far?)

    No my problem appears. The entire airport polygon drops several meters from 17.4m and with different elevations along the entire polygon. This instead of making the surrounding terrain "crawl" up the edge of my flatten :/

    If I also check the box "Feather outside polygon rather than inside", one of two things happen. Nothing, or if I change the pixelrange enough the airport polygon just sinks bak into the original elevation.


    What I'm I doing wrong here? :confused:
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2013
    I think your issue is that you need to create the terrain from the 17.4m polygon that is larger, then use the original polygon inside that the feather polygon and feather outside of it. The feather only works where 2 terrain layers overlap, so if you have the terrain only inside the inner boundary there isn't anything to feather outside of the boundary so you get no change.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • bsmavollanbsmavollan Global Mapper User Posts: 5
    edited October 2013
    Not sure I quite understand you, or if you misunderstood me. Here are som pictures of my scenario:

    første polygon.jpg
    Drawing my flatten polygon (only example poly)
    poly2.jpg
    Drawing my feather to poly
    3dview_foer.jpg
    3d view before I try to feather
    feather_step.jpg
    Featherstep
    3d_after.jpg
    3d view after feathering. Notice how much lower the flatten have become, also the extra "dent" in the left corner.

    I wonder if I have misunderstood the process :P
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2013
    You shouldn't create the terrain from the runway polygon, but instead the big outer polygon with an ELEVATION attribute assigned to it. Then select the runway polygon and go to the Feathering tab of the Options dialog for the new terrain layer and select to feather to the selected polygon (the inner runway), and check to feather outside the polygon. That should keep everything inside the runway at the desired height, then smoothly blend outside that into the terrain.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • bsmavollanbsmavollan Global Mapper User Posts: 5
    edited October 2013
    Aah, thank you. I got it to work now. Easy to misread some steps when skimming the posts :P
    Thanks a lot Mike :D
Sign In or Register to comment.