0

I've recently got some field erosion data. The only geographic data I have is the (lon, lat) (in degrees).

I need to plot the erosion against the slope, however, I do not have the slope yet.

Is it possible to calculate the slope from (lon, lat) coordinates? If so, how?

  • Welcome to GIS SE. As a new user, please take the Tour, which explains how our "Focused question / Best answer" model operates. Please Edit the question to specify the exact GIS software you are using and whether the data is vector or raster. Slope calculation in degrees is problematical, because the distance varies with each gap, so this is better performed in some equal area projection. – Vince Sep 3 '18 at 15:33
  • 5
    You will need height data, for example a digital elevation model (DEM) – BERA Sep 3 '18 at 15:43
  • thank you. Yes I do have a high resolution DEM for the Catchment area I'm working with. I was told I could use the long and lat values (together with the distance between the points) to calculate slope. But I was uncertain because I was sure I needed the vertical component. Thanks again! – 22Shanice Sep 4 '18 at 10:03
3

Short Answer

No. It is not possible to calculate slope from only latitude and longitude coordinates (or from only any other form of XY coordinates or horizontal-only data).

Additional Information

Calculating slope requires both horizonatal and vertical coordinates. The vertical coordinate is often referred to as the 'Z' coordinate (and 'X' is the easting or longitude and 'Y' is the northing or latitude). You need X, Y and Z to calculate slope. It is not possible with X and Y alone.

(Technically, you need horizontal distance, and vertical difference. Horizontal distance is usually calculated from X & Y coordinates, and vertical difference from Z coordiantes. Hence the requirement for X, Y & Z coordinates.)

As @BERA suggested, a DEM (digital elevation model) is often used to generate slope data. A DEM is a raster dataset (think of it as an image) where each XY cell (pixel) is represented by a Z value for elevation. Most GIS applications include tools to generate slope data from a DEM (either steepness and/or direction of slope). You may be able to find a free DEM for your area, eg from your government, however free ones are often of a low resolution and may not be good enough for your purposes.

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.