1

I have a shapefile that contains elevation data. I want to eventually convert this to a slope layer. I'm assuming I have to convert to a raster, then a DEM, then slope.

Is that correct?

If so, could someone point me in the right direction?

I'm not very familiar with the program.

enter image description here

When I try to use the inverse distance weighted method, I get a layer that has one point only. It cover the entire area of my original layer and more.

enter image description here enter image description here

  • Your data is in UTM Zone 16N Geographic, save it as UTM Zone 16N Projected in meters, determine the size of the grid squares then run the interpolation using the grid square values. This is just a best guess on my part, but if your search radius is 100 then it is looking at a radius of 100 degrees rather than a metric unit. – jbgramm Dec 2 '18 at 1:23
  • I right clicked on the layer/Set Layer CRS. I chose NAD83/UTM zone 16N. Is that correct? If so, I still get the same result. – jdeere9750 Dec 2 '18 at 4:02
  • That seems correct to me, but just checking from here. In the layer box, you right clicked on the layer, chose Save As, then created a shape file of the points, and chose NAD83/UTM Zone 16N, added the file to the map, ran the interpolation routine using the new layer, and got the same result? Highlight the new layer, and view the table to see if there are elevations for each point, and if they are different. If they are not different, then there is something wrong with the creation of the points in an earlier process. Some sample data would help if possible. – jbgramm Dec 2 '18 at 15:11
  • I was just trying to change the CRS of the layer. Once I saved it and reloaded the new layer in, its works correctly now. Thanks. – jdeere9750 Dec 3 '18 at 20:46
1

You can use Saga geoalgoritms that provided with Qgis. 0) Open your shape layer with points 1) Activate panel Geotools rightclicking on the tool strip and chosing Geotool panel 2) Processing toolbox will appear on the right side of the main window 3) Select tree node Saga (2.3.2) 4) Select tree node raster creation tool 5) Choose some particular method of interpolation like Interpolate(cubic spline) 6) The following dialogue will appear Dialogue

7) Click Run button 8) After performing the operation something like that will appear The result of creating grid 9) If you'd like to create a slope grid then among Saga geoalgorithms choose Terrain Analysis - Morphometry - Slope, Aspect, Curvature 10) You will see a dialogue that allows you to calculate several grids including
Slope Resulting grid

  • Thanks for your help. I'm having trouble with the Interopolation. I edited my original post to include pictures. – jdeere9750 Dec 2 '18 at 0:20
  • Could you send me your data or at least some portion of them? – Vadym Dec 2 '18 at 6:27
  • From what I see I suspect that you have original data in longitude latitude. You should right click on your layer Elevation Surface and choose option Save as and in the following dialogue point different coordinate system (NAD or UTM) and type a new file name. Then you should repeat all the operations with that new file. – Vadym Dec 2 '18 at 6:38
  • Once I got the original layer into the correct projection, your steps worked perfectly. Thank you. – jdeere9750 Dec 3 '18 at 20:46
  • You are welcome – Vadym Dec 4 '18 at 16:58

Your Answer

By clicking "Post Your Answer", you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.