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I am trying to calculate distances from parks in a small part of town. I have road centerlines (MultiLineString) and park entrances (Point) and want to use QNEAT3 to create iso-areas as polygons showing .1, .25. and .5 mile distances from entrances. Whenever I use any of the iso-area tools from QNEAT3 it creates an interpolation image and a polygon layer, but the polygon layer does not actually exist. It has no data in the attribute table and no polygons actually appear.

I've tried many different distance values in case the issue was units, but nothing changed.

Is it possible the multilinestring centerlines do not work?

See attached pictures for the output I'm getting vs the style I'm hoping to get.

I also have the street centerline data from opennyc (https://data.cityofnewyork.us/City-Government/NYC-Street-Centerline-CSCL-/exjm-f27b) but the point data for the park entrances was collected for this project.

last thoughts: I read in one article that matplotlib is necessary for QNEAT3, but have been unable to install or verify that it is actually necessary.

I also have already used the network analysis service area (from layer) to create service areas for each distance, but have not found a satisfactory way to create similar isochrone visualizations from those. That could also possibly solve my problem.

See attached pictures for what the output I'm getting

vs an example of the type I'm hoping to get

what I'm trying to get

lines

interpolation only

settings

enter image description here

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  • I collected the the park entrances data on my own using the fulcrum app, but the roads came from opennyc I can post that link.
    – Sarah631
    Commented Mar 20, 2022 at 18:56
  • I tried you network layer and created a point layer with 3 points. This worked perfectly with Iso-Area as Contours (from Layer) as you can see on this screenshot (red lines): i.sstatic.net/OCYP5.png Can you post a similar screenshot showing you point layer and the settings you make?
    – Babel
    Commented Mar 20, 2022 at 20:17
  • Thank you so much for trying to help me out! I really appreciate it. I tried doing the same as your settings but still didn't get any lines. Ill attach a screen shot of what I did and how it turned out
    – Sarah631
    Commented Mar 20, 2022 at 20:31
  • On your screenshot, I can't see the settings you make in the QNEAT3 dialog window. What does the Output contours layer's attribute table show you: do you have any features there? Try using the 3 sample points I used to see if that works: drive.switch.ch/index.php/s/wTbbE54WG6WfeI5
    – Babel
    Commented Mar 20, 2022 at 20:40
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    I found a solution for the project I'm working on - though it's probably not ideal. Seems to be an issue with Mac iOS and matplotlib and newer versions of qgis. I installed QGIS 3.14 instead with older python and matplotlib and it works. Thank you so much for all your help though! github.com/root676/QNEAT3/issues/42
    – Sarah631
    Commented Mar 21, 2022 at 20:57

1 Answer 1

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Solution found in GitHub at No output polygons or contours in QGIS 3.16.3 (OS X).

Seems to be issue with newer versions of iOS, QGIS, matplotlib, or Python.

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