QGIS 3.12 showing results of two different network analysis runs.  The one on the right used the built in network analysis point to point algorthym.  The one on the left is using the QNEAT3 plugin OD Matrix from Layers as Table (m:n).

I'm working on a project that is checking to see if distance is related to colonization by invasive species based on human activity. In order to do that, I must calculate the distances between colonized lakes and uncolonized lakes in a variety of forms. I have done this using QGIS 3.12 by using the built in network analysis run point to point, and then the QNEAT3 plugin using the OD Matrix from Layers as Table (m:n). Both result in very similar values, but these values don't have units and I am unable to figure out what they are. The layers have units of degrees, but can't be degrees. Google and StackExchange searching has not lead me to any answers, and neither did reading the manual for QGIS or QNEAT3. I could guess at meters,but a distance of 190-191 km is way to high. If it is in feet,its way to low. It's actually only about 11 miles or so between the points. I could just go with the "cost" values, but I need actual units, not values.

Doing one or two of these wouldn't be bad, but I have potentially thousands that will need to be calculated set over many states, and I don't have 5 years to do that on google.

If anyone could let me know either what the units are, or how to convert them to km or miles, or both, please let me know.


Greg W.

Google map distance calculation of same lakes

  • 3
    Have you tried converting your data to the correct UTM zone? – Erik May 13 '20 at 6:11
  • 1
    Your coordinates in the output image look weird, did you try to project your layer into a CRS? – Taras May 13 '20 at 6:48
  • Hi, which kind of routing strategy did you choose? I suppose it is the distance strategy? And as Erik and Taras suggested, pls reproject the layers - this will ensure that the output units will match the CRS units. – root676 May 13 '20 at 8:41
  • 1
    Your screenshot shows a cost on graph of 17940 for the point to point algorithm. The 11.1 miles from your second screenshot is 17860 meters. I dont think a difference of 80 meters is that much, so maybe the algorithm is in meters and already works with the projection you are using – Dataform May 13 '20 at 9:12
  • 1
    Thanks all. The units in the QNEAT3 distance matrix is in meters. When converted to miles gives an answer close to what google maps is showing. Apparently I "forgot" to convert from km to miles. One of those days. – gwfami May 13 '20 at 20:18

Your Answer

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

Browse other questions tagged or ask your own question.