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I am trying to make transport accessibility map in QGIS, using QNEAT3 plugin to build isochrones. I need to make a map, that shows 30 minutes area of accessibility with 5 minutes interval zones.
I am using Iso-Area as Polygons (from Layer) option and Fastest Path (time optimization) in Path type to calculate.

enter image description here
enter image description here I can't understand what units should i use in Size of Iso-Area and Contour Interval. I was trying to enter hours (0,5 for 30 mins and 0,083 for 5 mins) as in advanced parameters default speed is in km/h. But with this small values plugin doesn't work.

band_in = ds_in.GetRasterBand(1)
AttributeError: 'NoneType' object has no attribute 'GetRasterBand'

As far as I understand it is because QNEAT can't make a single cell to create a raster file.

The question is: what values/units should I use if I want to get time (not distance) accessibility?

  • From my personal tests i would say it is in seconds. But I encountered the same problem as you when using QGIS 3.8. Having no problems when using QGIS 3.4 (exactly the same settings) though. Which version do you use? – MrXsquared Jul 12 '19 at 15:24
  • I am using QGIS 3.4.6. Following to you and setting values in seconds, result appears truthful to me, thanks! But i should notice that if you have optional parameter Speed field in Advanced parameters, it must be set in km/h not in km/sec, or you will have the same issue. – Kerbl4 Jul 12 '19 at 17:45
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    If your question is solved, you can post your comment as answer, so it will help others having the same question. – MrXsquared Jul 12 '19 at 18:14
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You should use seconds in Size of Iso-Area and Contour Interval. Also, if you have optional parameter Speed field, it's input should be in km/h.

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