Options for creating elevation maps for a farm? - Page 4 - The Combine Forum
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post #31 of 39 (permalink) Old 07-08-2019, 02:33 PM
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Apparently QGIS can import those files and convert them to other things. There are some google hits on this topic anyway.

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post #32 of 39 (permalink) Old 07-08-2019, 05:31 PM
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I can put them on a map for you if you like, it only takes about 2 minutes.

Marg at AltaLIS is usually super helpful if you email them. Just tell her you got the wrong format and she'll usually send you the right one.

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post #33 of 39 (permalink) Old 07-08-2019, 07:16 PM Thread Starter
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I did download the QGIS this morning, took a while, just came back and got it installed, have a very nice map now, but don't see any way to read the elevations off of it. Can even see the boundaries of most properties thanks to roads and ridges around fields, so don't even need to overlay a map. I attached a snip of the program, what option am I missing to get elevations to show up numerically?
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post #34 of 39 (permalink) Old 07-08-2019, 07:47 PM
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I don't know much at all about qgis, unfortunately. QGIS has a steep learning curve. Another thing on my long list of things to learn about.

I believe there are plugins the interpret the data as a height map (colorized perhaps). Google suggests there are various plugins for creating height maps from your GIS data (including DEM): https://plugins.qgis.org/plugins/HeightmapExport/ might be one, although I'm not sure. Also there is a way to get data under the mouse cursor: https://gis.stackexchange.com/questi...points-in-qgis
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post #35 of 39 (permalink) Old 07-08-2019, 10:13 PM
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post #36 of 39 (permalink) Old 07-08-2019, 11:42 PM
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In computer gaming there is a technique called mesh based terrain. The section paths in AOG are made by using triangle strips. You only have to have the first two points then subsequent triangles need only a new point and use the previous two. This way you require roughly 1/3 the points to make a strip made up of triangles. Put a bunch of strips side by side and you have a plane - or a terrain. Now you add the vertical dimension at each point to make it 3d where the points come from a heightfield usually in the form of an image where the pixel value determines the height (elevation) of that point. Wrap a texture over the mesh, and you have a world to run around in.



Easy enough to do in AOG, drive around capturing height and position data, create an xy grid, create a triangle strip mesh, with the heightfield information and voila, you have an accurate as you want elevation map.
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post #37 of 39 (permalink) Old 07-11-2019, 02:05 PM
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I gave jvw a quick tutorial on QGIS, via sharing my desktop remotely. I think he figured out what he wanted to do. To import the XYZ data, use Layer->Import raster. You need to set the coordinate system for the layer. In his case, it was UTM 11N. Also, set the coordinate system for "on-the-fly" projection, bottom right corner. You want that in the same system so your view is not distorted.

If you double click on the layer, you can change the "Symbology". E.g. instead of a grayscale image, get colors from blue to red based on elevation. You can control the range of colors, etc. Lots of options there but a bit of a learning curve.

To see contours, use Raster-> Extraction -> Contour. Enter the spacing between contour lines. In his case, the elevation was in meters. If you make the distance too small, you will get very many contour lines and it will look a mess. Too few and you don't see the "lay of the land".

Contours show up as a separate layer. You can drag the layer above or below the raster layer. You can also change the color and transparency of the layers by double clicking on the layer.

If you want to see quarter section boundaries, QGIS can do that too. For Alberta, go here to get the "shapefiles" that contain the spacial vector data (free download after you register):

https://open.alberta.ca/opendata/pro...hip-system-ats

In the file I downloaded, the shapefile with the quarter sections is "V4-1_QTR.shp". In QGIS, do Layer-> Add vector.


To see quarter section properties, use the "Identify features" tool (View -> Identify features). You should get a box on right that shows feature properties. In there will be the legal land location (qtr, sect, twp, rng, mer).
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post #38 of 39 (permalink) Old 07-11-2019, 05:16 PM Thread Starter
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Thanks again to skfarmer for taking the time to show me all that, and add the instructions on here.

For a total investment of $100 for a township, and using the free viewing program, I'd say this is a good solution, at least for planning a tool. When I zoom into the pixel level, the 15 meter grid size doesn't miss very many features in our terrain, other than existing narrow ditches, but even they occasionally show up if they are on a diagonal at all.


I found it is very helpful, whenever you zoom into to a specific area, to reset the max and min elevations that will be coloured to the max and min elevations in the area of interest, makes a much more readable map when you have the entire spectrum representing elevations instead of only a couple of shades because there is a massive (and very colorful) hill 2 miles away of no interest at all to me.

Now I need to figure out if there is a volume add on that would calculate the volume of dirt within a given area to a certain depth or slope. Lots of help on Google, will be looking for this next.
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post #39 of 39 (permalink) Old 07-12-2019, 02:37 PM
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Seems not too hard. Been meaning to do this for a while, vr based on elevation maps i think have real merit, especially listening to Dr Ross McKenzie about it. Using science from the 1940's in greenhouses is how most prescription maps are still made today. As he says so many farmers are just using pretty pictures to make bad decisions.



Anyway, the map can be made as tight of a resolution as you want. Just made this one with the sim. I'll see if i can put together a quick terrain mapping window with full 3d, lighting, and water level that can be moved up thru the elevation.
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