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8. LUPMIS Tools > 8.3 Processing Tools > 8.3.7 Altitude/DTM

8.3.7 Altitude / Digital Terrain Model (DTM)


Level of expertise required for this Chapter: Advanced; specifically for LUPMIS @ TCPD


The 2 download tools described below require reliable Internet access to download data from the Google GIS web server.


  • a) Download Point Grid for DTM


There are many ways to create a Digitial Terrain Model (DTM). The easiest might be from a grid of altitude points, which can be downloaded from Google through a Google API: Processing > Altitude / DTM > Download point grid for DTM:


> Enter the UTM coordinates of the bottom left (SW) corner of the grid to be downloaded > Select the number of readings (points). The maximum is approx.  1600 per day, i.e. a grid of 40 x 40 points, which takes some 80 minutes. > Select the distance between the points, which is determined by the scale of your work > Download, and wait the estimated time.

If your area is larger than the 40 x 40 x points, you have to continue after 24 hours.


The result shows in the Map Maker windows, described in LUPMIS:





  • b) Create DTM


In Map Maker, you can now create a DTM from these altitude grid points: Utilities > 3D surface utilities > Create surface > from Spot heights > Select ...alt_points... file > Z values are NOT stored in a separate database > Settings > Use closest value in 6 directions > Cell width: Distance between points in point DRA file> Save Surface > Define name of TER file > Save.




  • Create Contour Map

In Map Maker, you can create a contour map from the DTM: Utilities > 3D surface utilities > Export surface > As contours > Step 1 of 3: Choose source TER file > Step 2 of 3: Resolution: 10 samples per cell > Contour spacing: 3 or 5 m for large scale; more for small scale > Next step > Choose target file: Define name for DRA file > Save > Finish.



Examples of the result:





  • c) Create Contour Map

In Map Maker, you can create a contour map from the DTM: Utilities > 3D surface utilities > Export surface > As contours > Step 1 of 3: Choose source TER file > Step 2 of 3: Resolution: 10 samples per cell > Contour spacing: 3 or 5 m for large scale; more for small scale > Next step > Choose target file: Define name for DRA file > Save > Finish.



Examples of the result:





  • d) Download Spot Heights / Profile


You can also download spot heights for individual mapping or an altitude profile. This is limited to a number of 50. You can either create a line DRA file or enter the points manually: Processing > Altitude / DTM > Download spot heights / profile > Select DRA file or enter point coordinates > Download:




Example for a  profile (e.g. road profile):





- - - - -


Once you have a DTM, you can create a variety of altitude-related maps:


  • e) Create Raster Altitude Map


Processing > Altitude / DTM > Create altitude map




Examples of result:







Alternativ approach in Map Maker to create a TIF altitude bitmap from DTM: Utilities > 3D surface utilities > Create bitmap > Altitude > ... > No sunlight > Save as TIF file, with world file.


  • f) Create Slope Map




  • g) Create Hillshade Map


A hill shade map (raster, TIF file) can be created from altitude bitmap (TIF, created from DTM in Map Maker, recommended) or from JPG file (created in LUPMIS): Processing > Altitude / DTM > Create hill shade map




Example of result:


Alternative approach in Map Maker to convert DTM to a slope bitmap: Utilities > 3D surface utilities > Create bitmap > Slope > Select DTM > Sidelight: Light by sun at specified bearing and elevation.



  • h) Create Coloured Altitude map


An alternative coloured altitude map (raster, TIF) can be created from altitude bitmap (created from DTM, in Map Maker), alternatively from JPG file (created in LUPMIS): Drawing > Other GIS tools > Altitude / DTM > Create coloured altitude map

Alternativ approach in Map Maker to create altitude bitmap: Utilities > 3D surface utilities > Create bitmap > Altitude: Define colours by Colours > by Palette.





  




 
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