[Qgis-user] help with shortest-path/network analysis (multiple origins to multiple destinations)

Francesca Parente francescaparente.rse at gmail.com
Fri May 6 07:02:15 PDT 2022


Thank you very much indeed Nicolas, for your inputs and all the suggested
materials!
I have 50 targets and 532 origins. My goal is to define where is best to go
within the 50 destinations for each starting point - given the actual range
of choices though, so I'm not sure that running a batch one-to-many would
take into account all the variables properly as a many-to-many would do. In
the absence of a specific modelling, also some second best could work.

I understand that your upstream-downstream-Dijkstra script is suitable for
layer-to-layer indeed and I'm trying to run it, but at the >>> import
geopandas as gpd<< line I got the following error message:







*Traceback (most recent call last):  File
"C:\OSGEO4~1\apps\Python37\lib\code.py", line 90, in runcode    exec(code,
self.locals)  File "<input>", line 1, in <module>  File
"C:/OSGEO4~1/apps/qgis/./python\qgis\utils.py", line 799, in _import    mod
= _builtin_import(name, globals, locals, fromlist, level)*
*ModuleNotFoundError: No module named 'geopandas'*

I've been following your tutorial, but I admit I'm not quite familiar with
py. I've gone through the remaining import coding and it seems working, but
I'm not sure the "geopandas" module is needed or not to properly complete
the script.

Thanks again!!
Best,
Francesca

Il giorno gio 5 mag 2022 alle ore 22:28 Nicolas Cadieux <
njacadieux.gitlab at gmail.com> ha scritto:

> Hi,
>
> How many shortest path calculations are you looking at? You could probably
> do a all pairs shortest path dijkstra and filter the results.  You could
> batch multiple one to many (point to layers)  In QGIS using the processing
> plug-in.
>
> I did create an algorithm using networkX that could be modified to work
> with two input layers.  This could be useful if QGIS is not fast enough or
> if you have too many routes to calculate.  You will find it in the links
> below. Keep in mind this algorithm was for rivers therefore you have no
> trafic rules.  This would need more work.
>
> You will also find an article we wrote in Data that may help.  If you have
> trouble with the network, look in the QGIS hub for the models. Look for the
> 3 “fix directional networks models”.
>
> I added a few YouTube videos I made.
>
> https://gitlab.com/njacadieux/upstream_downstream_shortests_path_dijkstra
> <https://www.mdpi.com/2306-5729/5/1/8>
>
> https://www.mdpi.com/2306-5729/5/1/8
>
> https://plugins.qgis.org/models/
>
> https://youtu.be/v61PafSByvM
>
> https://youtu.be/qQrHcKtmr3o
>
>
> Nicolas Cadieux
> https://gitlab.com/njacadieux
>
> Le 5 mai 2022 à 10:38, Francesca Parente via Qgis-user <
> qgis-user at lists.osgeo.org> a écrit :
>
> 
> Hello everyone,
>
> I'd need to identify optimal destinations (within a point layer of
> geolocated facilities) for each territory of a given set of possible
> origins.
> I already calculated a distance matrix between the two point-layers, and
> also applied the distance-to-nearest-hub tool to generate a string layer
> and identify the optimal facilities.
> But I'd like to obtain a more realistic estimate, accounting for the roads
> network (and ideally their travel times). With quite a few issues, I
> finally managed to import an OSM road network from download.geofabrik.de
> (in order to cover my area of interest, I had to merge two different
> vectors fo Center and Southern Italy and then extract a focus spot in
> between the two and save it as a lighter layer, otherwise it also took an
> eternity to run every analysis).
>
> So now my question would be: is there a tool to perform a layer-to-layer
> shortest-path analysis that takes it into account?
> All that I could find was either point-to-point or
> layer-to-point/point-to-layer (I looked also at built-in network analysis
> tool and Qneat3 plugin).
>
> Any kind of inputs and suggestions will be more than welcome!
> Thanks a lot for your support and have a good day,
> Francesca
>
> --
> ----------------------------
> Francesca Parente
>
> _ SESS Euro PhD
> <https://phd.uniroma1.it/web/FRANCESCA-PARENTE_nT1602922_IT.aspx> in
> SocioEconomic and Statistical Studies
> _ Luiss SEP <https://sep.luiss.it/> School of European Political Economy
>
>
> email: francescaparente.rse at gmail.com
>        parentef at luiss.it
>
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>

-- 
----------------------------
Francesca Parente

_ SESS Euro PhD
<https://phd.uniroma1.it/web/FRANCESCA-PARENTE_nT1602922_IT.aspx> in
SocioEconomic and Statistical Studies
_ Luiss SEP <https://sep.luiss.it/> School of European Political Economy

email: francescaparente.rse at gmail.com
       parentef at luiss.it
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