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In QGIS 3.26.1, I used the QNEAT3 "OD Matrix from Layers as Table (m:n)" function. (Ancillary info: I am using the TIGER/Line 2019 primary and secondary road data for the US, in order to calculate fastest routes from each county centroid to each county centroid.) As optimization criterion I set fastest path. I also set the default speed to 88 km/h. Otherwise, the parameters for the function are the default settings.

After the calculation finishes, I receive values between 0 and 2. However, upon reading a similar Q&A at Interpreting total cost variable in QNEAT 3 OD Matrix using QGIS I am expecting the results to be reported in terms of seconds traveled between points in the layers. Given that I am looking for county to county road travel times, the results don't seem to make sense to me. The only way to potentially make sense of the results is if they were reported in days, rather than seconds.

How can I make sense of the results that I get?

Are they really reported in seconds, as stated in the above thread?

Did something go wrong with how I am using the algorithm or my input data?

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  • What CRS is your layer in? What units does it use for measurements?
    – Babel
    Aug 15, 2022 at 15:57
  • The CRS is NAD83 (EPSG:4269), and the unit of measurements are m and m². The value for Elipsoid (for distance and area calculations) is: GRS 1980 (EPSG: 7019). Is that what you meant?
    – Benjamin
    Aug 15, 2022 at 19:41

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After looking closer into the results that I get, I am now fairly confident that they are reported in days, instead of seconds. I cross-checked my results with google maps driving times, and this makes sense to me. I have played around a little bit also with subsets of my data and reporting in terms of days seems to be a general feature of the results that I get for time optimization, i.e. this is not dependent on duration/distance becoming very large. I have also tried a little bit with changing the CRS and that didn't change anything for me. In any case, I am now happy to be able to interpret the results that I get :).

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