Generate Areas with Contours

NokluNoklu Global Mapper UserPosts: 29Trusted User
edited April 2013 in Vector Data
I am trying to generate color filled areas based on the shader features along with the contours. My understanding of this feature is, it will generate polygons based on the currently loaded shader (at least that is what the dialog box says). I have the slope shader loaded and adjusted the way I like it. Everytime I run this it generates polygons based on the atlas shader (even though it is not loaded). Does this only work with the Atlas shader? I am trying to generate slope areas so I can bring them into AutoCAD.

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited May 2011
    The generated contour areas will be colored based on the currently selected "elevation" shader since the areas are iso-height areas. Since the slope shader applies to the slope values of the elevation grid and not the elevations, the slope shader coloring isn't applied since the areas generated aren't areas of constant slope but instead of constant elevation, so a single color wouldn't apply.

    What you could do is export your data to a Float/Grid file with slope values using the File->Export Elevation DAta menu command, then load that back in and setup a custom shader that colors that how you want based on the slope values that are now interpreted as elevations, then you could generate contour areas out of that and you would really be generating areas of similar slope and not similar elevation.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • laughlinlaughlin Global Mapper User Posts: 18Trusted User
    edited April 2013
    This sounds just the ticket for something similar i'm tackling, trying to create polygons for areas of similar slope. Got as far as the float file export and loading that with custom 'slope shader' values. I'm using ranges of 0-5, 5-10 and 10-15 for the polygon layers i want to create. In the generate contours menu i did the first run with generate range (0-5), starting at minimum range value checked. Further down the dialog, i checked generate area features and smooth areas/lines. Under countour bound tab, i checked to crop to a box i had selected from the data layer control window. I seem to be doing something wrong and end up with data generated well beyond my target limits and the 0-5 degree slope range selected.

    Ultimately, just want to generate a series of slope area polygons (ex. 0-5, 5-10, 10-15 degrees) to load on an aerial draped over DEM to plan areas for field survey in field. I've done this the other way around following the thread on forum, altering the 'elev' values in float file export the custom ranges as separate exports. Works very well for isolating the slope range areas, aside from the 'background' which to needs to be set to transparent. But the slope range polygons themselves seem more portable for field use.

    Wondering if there is a work around with the contour area generation routine, using the slope value float file and the custom slope shader as starting point of export.

    thanks!
    Laughlin
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2013
    Laughlin,

    Yes you can quickly do this with the equal-value area creation from the Control Center! First set your shader to the Slope Shader on the toolbar, then right-click on your terrain layer in the Control Center and select to create areas from equal-value areas. Then specify the slope range (2.5 in your case so you get 5 degree wide areas). You should get areas covering each range that you want.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • laughlinlaughlin Global Mapper User Posts: 18Trusted User
    edited April 2013
    Mike,

    Thank you for the quick reply. Figured it was a simple matter of finding the built in functions i was looking for. When i do this though, i actually get concentric elevation value polygons. Perhaps i've missed a step. I have a DEM file loaded and selected the slope shader to render screen data in slope values. The vertical 'elev' legend agrees and all is in slope instead of elev. The right click to access equal areas seems to be providing the options and i've entered 2.5 in the 'allowed elev fuzziness' window. This is actually the only data option input i can access - screen shot attached.

    equal area window.PNG
    From here i end up with a busy layer of 2.5 m contour interval polygons, rather than actual slope area polygons. Thought GM simply read slope as equiv to elev in processing at this point as the setting change had been made from the shader selection. Wondering if the DEM file format might need to be converted beforehand. (Though, GM has no trouble reading the elev data interpreting slope factors from it on screen). Suspect there is something i may be doing wrong here.


    Appreciate any pointers,
    thanks,
    Laughlin
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2013
    Laughlin,

    What version of Global Mapper are you using? Initially the equal-value area always did elevations regardless of whether the slope shader was selected. Starting with v13.2 I think if you have the Slope Shader selected then you should see 'Slope' text on the equal value area setup dialog and not elevation like you are seeing. So I'm guessing you have an older version.

    Thanks,

    Mike
    Global Mapper Guru
    gmsupport@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • laughlinlaughlin Global Mapper User Posts: 18Trusted User
    edited April 2013
    Hi Mike,


    As you suspected, I am using ver 12.02. But, i did just manage to solve the problem. I was working off the DEM file itself, thinking that GM would read the slope values based on the slope shader being selected. Tried another way around and went with the FLT file of custom slope limits I had initially generated form the DEM. Using this as the input data I was able output to shapefile with all slope area polygons. From there it is a snap to search by a value (ie 5°) and copy/paste to create custom slope area layers of constant value.

    This is proving very useful in cross-validating the results of a predictive model passed along from an ArcGIS user. Seems to offer flexible possibilities for refining fieldwork targets, esp with the 3D viewer in tandem - which is missing on other end of the chain .


    I suspect i am probably overdue for an upgrade to latest of ver 14. A lot of great features in there to put to good use.

    thanks for the superb support and product development!
    Laughlin
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2013
    Laughlin,

    Yep that is the work-around in older versions, export to FLT as a slope grid and then bring that in with the slopes as elevations. Of course everything is much easier in v14 :)

    Thanks,

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