Roughness

alix_pradelalix_pradel Global Mapper UserPosts: 3
edited June 2010 in Suggestion Box
Hello,
I am using GM quite often for some wind turbines energy assessment projects,
I would like to use a roughness grid with points that have a roughness attribute value.
I would like to use it as a wasp.map but I don’t know how to convert the roughness from those points to roughness lines that must have two attributes :

• ROUGH_R (The Roughness on the right of the line)
• ROUGH_L (The Roughness on the left of the line)

For the elevation part of the *.map, it is possible to convert the points grids by using “generate contours” but this is not working for the roughness because a line could meet another line (which is not possible with elevation contour lines).

Have you ever heard of this problem and do you think we could have a way to solve it in the future ? I think it could be possible for GM to generate lines from those points.

Thank you very much in advance for your reply,

Best regards.

Alix Pradel

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited December 2009
    Alix,

    I think it would be fairly simply for me to add an option to the "Generate Contours" command to treat the "elevation" values as roughness and thus add ROUGH_L and ROUGH_R parameters. However, I don't see any way that I could make lines meet when generating contours from roughness vs elevation as a precondition of the contour generation is that they don't meet (they can get arbitrarily close though). I'm not sure how you would derive intersecting lines from a set of points. Is the intersection important?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmappersoftware.com
  • alix_pradelalix_pradel Global Mapper User Posts: 3
    edited March 2010
    Mike,

    First tank you very much for your reply.

    Intersections are not so important but it is the problem...

    Imagine a simple roughness grid with three areas:
    a lake (with points attributes roughness=0.05)
    a field (r=0.3)
    a forest (r=0.8)
    Between two areas i can generate countours and a line will be created and I could give ROUGH_R and ROUGH_L to it. But at the point which is the intersection between the three areas it won't work and it will generate an error.

    I am not an expert but I imagine that there is a solution to generate 3 lines : lake/field lake/forest and field forest which meet at the intersetion point.

    I wish you understand my problem,

    Best regards,

    Alix Pradel
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited March 2010
    Alix,

    I think the real issue is that for contour generation there is no such thing as a non-continuous change in value, there is always some gradient from one elevation value to another (although it may be very steep). So when you generate contours from a grid of rougness points there will always be a series of contours created at the transition from one roughness value to another.

    I think what you may need to do is create the contours by specifying a single contour value (one for just above or below each roughness value, like 0.05001 to be above the minimum, and 0.7999 to be just below the maximum). Then you can break those contours up (use the split option in the Digitizer Tool) to assign ROUGH_L and ROUGH_R values where they have different roughness values as the line goes along a different surface type.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • alix_pradelalix_pradel Global Mapper User Posts: 3
    edited March 2010
    Ok, thank you I will try it tommorrow
  • AdamHAdamH Global Mapper User Posts: 2
    edited June 2010
    Are the Rough_L and Rough_R defined as one would travel along the line counterclockwise or clockwise?

    Thanks in advance.

    -Adam
  • AdamHAdamH Global Mapper User Posts: 2
    edited June 2010
    Now I'm thinking that it may not matter just so long as one is consistent?
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited June 2010
    For lines there isn't a counter-clockwise or clockwise notion. The ROUGH_R and ROUGH_L for lines will be relative to traveling from the first vertex in the line to the last vertex in the line.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
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