Global Mapper Pro

Contour lines - Can I add more? Can I create a smooth transition between lines?

Hello,
I'm taking a contour data found within a shape file and trying to convert it, using Global Mapper, into a .ter (Terragen) file.
I'm run into a problem where the data I'm pulling into Terragen has too extreme a vertical step between contour lines.  I apologize for not using the correct terminology but I'm knew to this subject matter.
Is there a way within Global Mapper to either add more contours so as to increase the step density and hide the steps or even better can I insert some form of data into the outputted file that say this is a smooth transition between contour lines vs. having someone run up the Inca trail all over my renderings.
Any help would be greatly appreciated.
The grey file is what was rendered in Terragen.
The two blue files are the approximate same areas as displayed in Global Mapper.
Regards,
Tudor
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Answers

  • Mykle
    Mykle Global Mapper User Trusted User
    Hello Tudor,
    Contours are normally generated from an elevation surface like a DEM.  If you don't have an elevation surface, you can create one from other available elevation data, like a collection of data points. 

    Contour data can be used to create an elevation surface if elevations are included.  That sounds funny, but I find lots of files of contours that don't have elevations assigned to the lines, at least in a way that Global Mapper can use them.  At times I have manually assigned elevations to the lines, and that works (tedious).  That assumes that I can identify the elevations for some of the lines, and figure out the others. 

    If you have steep slopes, then your elevation surface will need to have enough resolution to allow contours to be generated that don't overlap. 

    Otherwise, you could manually edit your contour lines by moving some vertices as needed.  You can also add more lines where needed.  Hopefully this detail would be needed for no more than a small area. 

    Your terrain looks like it has a few cliffs rather than smooth, if steep, slopes.  Contours can be very interesting in cliffs. 
    Mykle
  • Hello Mykle
    I appreciate the response.
    I believe the file has the elevation data but it seems to be exporting it as a step and not a gradient.  Can Global Mapper increase the number of contours?  Essentially making the steps smaller?  Manually drawing them in is not going to be feasible.
    Tudor
  • bmg_bob
    bmg_bob Global Mapper Programmer
    Hello,
    tudor said:
    I believe the file has the elevation data but it seems to be exporting it as a step and not a gradient.  Can Global Mapper increase the number of contours?  Essentially making the steps smaller?  Manually drawing them in is not going to be feasible.


    The only way to increase the number of contours when they are created from the original elevation data.  Do you have access to that data?

    I assume that you created the elevation grid for export to Terragen using Analysis | Create Elevation Grid from 3D Vector/Lidar Data.  Is this correct?  If so, what settings did you use on the Elevation Grid Creation Options screen?  Did you try changing the settings for "Flatten 3D Area Features" and "Taper 3D Area Features Using Curve Value"?

    From the Help documentation:

    Flatten 3D Area Features - When creating a terrain surface from a vector area feature this option will flatten the area based on the inherent Z value given in the area feature. When unchecked the area feature will inherit variable elevation based on the underlying ground elevations.

    Taper 3D Area Features Using Curve Value - When this option is checked the elevation data will taper to the highest most point using the given curve value. When unchecked the elevation data will shift sharply in order to exactly match height values at any given point.

    Cheers,

    Bob

  • Thanks Bob,
    I will give this a go and see what I'm able to produce.
    It sounds like the curve value issue might have some promise as I'm not sure if I checked that off or not.
    I appreciate the help.
    Regards,
    Tudor
  • Just did a quick search and it appears the curve only relates to the one layer interacting with another.  

    http://forum.globalmapperforum.com/discussion/10502/what-exactly-does-the-taper-3d-area-features-using-curve-value-do

    I had in fact already checked it off in a blind fumble to resolve my issue.
    No dice I'm afraid.
    Tudor
  • bmg_bob
    bmg_bob Global Mapper Programmer
    Hello,

    Have you tried downloading elevation data from an online data source (File | Download Online Imagery/Topo/Terrain Maps) for the area where your contours are, then using that to create new contours?  That will give you more control over the process of creating contours.

    Cheers,

    Bob
  • I will give that a go
    The issue I'm having is that the Shape files I have are very accurate (from a mining company's surveyors) just not very dense in detail.  I think they are 1m detail and the tundra doesn't have a huge vertical range.  Can Global Mapper take both sources and combine them?
    Tudor
  • bmg_bob
    bmg_bob Global Mapper Programmer
    tudor said:
    I will give that a go
    The issue I'm having is that the Shape files I have are very accurate (from a mining company's surveyors) just not very dense in detail.  I think they are 1m detail and the tundra doesn't have a huge vertical range.  Can Global Mapper take both sources and combine them?
    If you create contours from the elevation data, you will be able to specify the vertical distance between contour lines, which should produce more of them.  You could actually export the downloaded elevation data directly to the Terragen file, and not use the contours at all.

    Cheers,

    Bob
  • Mykle
    Mykle Global Mapper User Trusted User
    edited June 2016
    Okay, back up to the original question.

    The problem is the terraced appearance of the terrain in Terragen.  It looks fine in Global Mapper. 
    I can generate contours from an elevation grid, turn off the elevation grid, then create a grid from the contours, and the shaded appearance in GM is still NOT terraced. 

    Given that Terragen is creating terraces along the contour lines, is it possible to turn off the contour line display and export only the elevation grid for Terragen?

  • Mykle said:
    ...Given that Terragen is creating terraces along the contour lines, is it possible to turn off the contour line display and export only the elevation grid for Terragen?
    When I export a raster/image format I was seeing the contour lines (hence one the samples I showed resulted in something similar in a GeoTIFF.  But when I exported the .ter file I am pretty sure I only export the generated elevation grid.  Am I using the wrong 'layer' within the Overlay Control Panel?  Attached is a close up of the layer I exported.  

    I really do appreciate all the help. 
    Sorry I feel like I'm asking a lot of awfully simple questions.  Still trying to get a handle on the software.


    Tudor
  • tjhb
    tjhb Global Mapper User Trusted User
    edited June 2016
    To me the terracing looks as if it is caused by the *.ter file being in integer format. A quick test export suggests it stores elevations as signed 32-bit integers, automatically converted to feet.

    If that is correct then elevations are being rounded to the nearest foot on export. Each region with the same rounded value shows as a terrace.

    If integer rounding is an inherent property of the *.ter format (I suspect it might be) then I would suggest trying a different export format which stores floating-point values.

    (If this is right then it also means that the problem has nothing to do with the contours, or the generation of a DEM in GM.)


  • tjhb
    tjhb Global Mapper User Trusted User
    edited June 2016
    I suggest you try exporting your elevation data to an ordinary GeoTIFF, using file type "Elevation (32-bit floating-point samples)" (not 16-bit integer).

    A quick test suggests that Terragen can digest this correctly, using either Add Terrain > Heightfield (load file) > TIFF or GeoTIFF, or just Add Terrain > Heightfield (load DEM).

    I haven't tried rendering yet (I'm literally just starting out with Terragen) and I don't know whether you must export from GM using feet rather than metres.
  • tjhb said:
    I suggest you try exporting your elevation data to an ordinary GeoTIFF, using file type "Elevation (32-bit floating-point samples)" (not 16-bit integer).
    This might have started to identify the problem... as expected... me.
    I don't have the option to select the Elevation File Type at all. (see attached image) 

    So one of two things are happening I assume.
    1. The file I have doesn't have elevation data as I had assumed.
    2. I'm not preparing the file correctly to allow me to use those file types.

    Thoughts?
    Tudor

  • tjhb
    tjhb Global Mapper User Trusted User
    Looks like you're exporting to "Raster/Image format".

    Instead, export to "Elevation Grid format".

    The GeoTIFF option appears for both, but the available options are different. Easy to get them confused.
  • That was it!
    Thanks very much I've actually been able to import non-stepped data into Terragen.
    I really appreciate everyones help.
    Sincerely,
    Tudor
  • Still need to work on the textures but here is a sample I've since created without the banding.
  • tjhb
    tjhb Global Mapper User Trusted User
    Great, and thanks for the example.

    Maybe we'll meet on the Terragen forums too. I'm tjhb there as well but am only a lurker so far. A complete beginner but very excited about the massive possibilities.

    (I thought the tiger was just a deep ripple until I did a double take. Cool.)

    Tim
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