Combine terrain - coloring based on change

Hello, 

I'm fairly new to Global Mapper, I've been working on self-training for a couple of weeks, I've watched literally every tutorial on their YouTube channel for LiDAR processing (awesome videos by the way!)

I'm working with the "compare/combine terrain" feature. I'm wanting to do something I used to be able to do years ago when I worked with the Maptek I-Site Studio software, which was creation of a terrain/surface which is colored based on the changes between the surfaces being combined. 

I think I'd need to use either the addition, or subtraction function. I successfully created a new terrain based on change using subtraction, that is working OK, but I'd like to create the combined surface that is colored by change, similar to this screenshot I included. Basically say one TIN surface is a one color, and another is different color, when they are combined, they maintain their colors so you can see the change. Not just a new terrain that is elevated or colored based on the change. Not sure how to better explain it! The picture should, lol. That screenshot is old and from Maptek software. I'm just tinkering around with some scans of a stockpile in GM, I cropped off the top of the pile, created two terrains, one of all the points, one with the cropped top, and doing some terrain comparisons trying to get the top of the resulting terrain file to show the Atlas shader or a solid color, but the points on top of the pile are a different color range, 

I think this better visualizes the change over time through various laser scans of this area. They are just TIN surfacesI tried tinkering with creating custom shaders and shading each terrain differently, then creating the combined terrain but it just wants to use one shader. 

Not sure if I am even close to figuring this out, or it is not possible, or whatever. Any help is appreciated. 


Best Answer

  • sphillipssphillips Posts: 142
    Answer ✓

    1- Original terrain with dump artificially flattened for illustrative purposes



    02 - New terrain with higher dump and 3 small artificially flattened areas to the west (this is so we can also show cut as well as fill later)



    03 - Combine/Compare Terrain Layers. Use Subtraction (Signed) and select New then Old. We use Signed so that we can see negative cut values as well as positive fill values.



    04 - Your result will look like this with the Atlas shader. Orange or 0m illustrates no change.




    05 - Create new 'Change' shader



    06 - Define as follows or choose your preferred colours. I've used red for fill and blue for cut. No change is set to white but do not use a different colour for this. When using the blend mode later it will become transparent.



    07 - Turn on the 'New' terrain layer and switch to the Daylight shader (use white as Surface Color - see Surface Color button in the image for step 05 at the top)



    08 - Turn on Combined Elevation terrain layer and double click it and go to the Display tab. Change the Blend Mode, select the custom shader called 'Change' and turn off the hill shading effects.


    09 - The following steps will be required if you wish to render a 3D view with the colouring applied. Unfortunately the above does not work in 3D view; only in plan.


    To begin Right-click on the Combined Elevation layer then Layer > Export and choose JPG2000 or similar image format. Make sure to check PRJ in the options. Do not export as an elevation grid though as we just want the colours.



    10 - Import the layer back in and double click it and go to the Display tab. Check the Texture Map option to apply the colour to the terrain. This can also be done via the Blend Mode if you choose.



    11 - Hit the 3D button on the main toolbar and capture your image using the Save Image button (Camera button on toolbar)



    Good luck!

    Steve

    Mykle

Answers

  • sphillipssphillips Posts: 142
    Hi,

    Can you share some data so I can show you how to do this? 

    Essentially you can colourise the underlying terrain with your combined terrain that is showing the difference. The key to doing this is via the Options > Display tab for the combined terrain that is sitting on top. On the Display tab choose the Multiple Blend Mode then choose your custom shader via the Shader drop-down and finally turn off the Use Global Enable/Disable Hill Shading Option and Use Hill Shading for this layer. What this does is to turn off the hill shading effect for the layer and to use the shader colours to colourise the existing hill shade used on the underlying terrain.

    Note that the main shader should be Daylight but probably best to change the Background Color for the shader via Configuration (wrench icon) > Shader Options > Surface Color. Personally I'd go for white but you could choose that delicious green from the image above!

    Good luck!
    Steve

    P.S. I assume you work in a Mining like me judging by the screenshot.
    orellius
  • orelliusorellius Posts: 10
    sphillips said:
    Hi,

    Can you share some data so I can show you how to do this? 

    Essentially you can colourise the underlying terrain with your combined terrain that is showing the difference. The key to doing this is via the Options > Display tab for the combined terrain that is sitting on top. On the Display tab choose the Multiple Blend Mode then choose your custom shader via the Shader drop-down and finally turn off the Use Global Enable/Disable Hill Shading Option and Use Hill Shading for this layer. What this does is to turn off the hill shading effect for the layer and to use the shader colours to colourise the existing hill shade used on the underlying terrain.

    Note that the main shader should be Daylight but probably best to change the Background Color for the shader via Configuration (wrench icon) > Shader Options > Surface Color. Personally I'd go for white but you could choose that delicious green from the image above!

    Good luck!
    Steve

    P.S. I assume you work in a Mining like me judging by the screenshot.
    Thanks very much for the reply! I actually work at a large survey equipment dealer in Canada, my job is the UAV/scanner nerd, I do the drone and scanner sales demos and customer training. Mostly with the drones, so point clouds from photogrammetry. We used to do some work with the Maptek products years back. I do a lot of work in the mining industry for sure, mostly construction/survey though. My goal is to integrate Global Mapper to my workflow and push that to customers so they purchase and use the software, and become a reseller...just looking for cool ways to present the data to customers to get them interested. 

    Sorry for the long ass post, hard to get the details out in a shorter form!

    Anyway, I've toyed with your suggestions for a while and can't get it to work. Not sure if it is due to the TINs sharing the same common area? Meaning the "material" added to the pile is not in surface of it's own, it's one surface of the whole area, and another one of the same area, but the one pile has more material on top of it. So I want it to show the difference between them, highlighting where the change is, which should only be the pile. 

    Not sure if I am trying to simulate something that will never work. I'm providing a link to some data. I don't have the data anymore from that first screenshot, probably deleted it years ago when I stopped working with the Maptek software.  To clarify, this pile I'm providing never changed, this is the exact same data, I only simulated the pile changing by deleting some points from the top and creating a new TIN, pretending it was a previous survey. I always use GCP and UAVs with RTK/PPK, so the data is always very accurate, but if this was a real world survey (2 different flights) then there would be a difference across the entire site, even if it is very slight (1-2cm vertical difference just due to the nature of GNSS, and the photogrammetry). So even if we did find a way to highlight the differences, it would need to be able to accentuate the difference where there is a major difference (i.e the pile) and not so much where there is only a minor difference (the little variances in elevation due to RTK/PPK). I don't have any data at the moment that shows the same site, with an actual pile change, that I flew at 2 different times, so I am trying to pretend...lol. 

    If I create a surface of ONLY the changed points on the pile, of course I can get that to show as one color, because the other surface is a much larger area, the pile change just sits there. But ultimately it needs to be 2 surfaces, and it highlights the changes in different colors, OR a single surface, that is the addition/combination of the two, which highlights the difference it found during the calculation.  

    I created a custom "red" shader, it only has 2 values, 0m = red, 2000m = red. This covers all elevation ranges. Sure I can do one at the actual elevation ranges for this data (150m-165m) and shade it white to red or something, but the red/red shows well when you use the hill shader. Perhaps this is where I'm screwing it up. I used RED shader for the top surface (the new pile), and daylight shader (white) for the lower surface (old pile), turned off the hill shading on top surface, chose blend mode "multiply" (there is no "multiple" option). When I do this, basically I get the underlying terrain shaded in Red, the new pile kind of disappears. I show this in the last screenshot. That solid red blob is just because the hill shading is off, and the color range for the shader is red/red so it doesnt differentiate the elevations. 

    Here is a download link to the two surfaces, if you don't mind seeing what you can do. 

    And a screenshot of what the data looks like, you can clearly see where I manually deleted points off the pile, looks cheesy but should work to simulate this. <span>:smile:</span>






  • orelliusorellius Posts: 10
    download link is coming. I'll post it in a bit
  • orelliusorellius Posts: 10
    Not sure how to edit the original post...

    Download: https://we.tl/t-5oW1TK9oGt
  • orelliusorellius Posts: 10
    This is awesome, thanks for taking the time to work through and post this! I'll work through this today or tomorrow myself to make sure I can replicate this. Looks like exactly what I was trying to do. Cheers!
    sphillips
  • sphillipssphillips Posts: 142
    orellius said:
    This is awesome, thanks for taking the time to work through and post this! I'll work through this today or tomorrow myself to make sure I can replicate this. Looks like exactly what I was trying to do. Cheers!
    You're very welcome. Note that you can also apply a gradient shader as follows:


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