[Qgis-user] Map Matching

Fri May 24 01:33:53 PDT 2019

Hi Chintan,

I had a look on the data you provided:

1. I just found the DBF-file, not the whole SHAPE, so I could not reproduce the problem with your data.
2. The DBF contains over 60.000 data sets, I think that is the network.
3. The screenshot you provided does not show a problem, but it looks like the plugin is still running (check the task manager to confirm it).

If you are using a very big network, than the plugin will slow down. Please read the detailed description of the plugin in the README on GitHub. In short:
The plugin hangs on the task „calculating transition probabilities“. Transitions are a pair of two candidates, i.e. points on the network that could represent trajectory points. For each transition the shortest route on the network will be calculated using the Dijkstra algorithm. Dijkstra steps through all nodes of the network to find the nearest  parent node. If you are using a big network with a lot of nodes, this task needs some time. Especially if you have a lot of candidates and transitions (because of outliers, a too big maximum search distance or something else) and the task has to be repeated very often. So my advice for you is to use a spatial filter before you start the plugin:

1. create a line from your trajectory (e.g. using points to line)
2. create a buffer from the line (e.g. 500m)
3. clip the network using the buffer as clipping mask
4. run the plugin with the clipped network

I will integrate this task in the plugin in a future version. But the plugin is a free time project and actually I am working on another project. So the new version will take some time. Please try the described workaround.

Sincerely,
Christoph

> Am 23.05.2019 um 02:25 schrieb Chintan Advani <chintanadvani at gmail.com>:
> 
> Hey Christoph,
> 
> I did understood the yesterdays error. I inputted the maximum distance for path search as 0 which was not an acceptable value. However after inputting some random value, the software hangs at a particular stage while it calculates the transition probabilities. I tried the same assignment with different input values but each time it gets stuck at this point. I am attaching the image of the dialogue box where the process stops. I hope there is a solution to this error.
> 
> <offline matching error.PNG>
> 
> Thanks and Regards,
> __________________________________________
> Advani Chintan Sanjeev
>         Research Scholar,
>         Civil Engineering and Build Environment,
>         Queensland University of Technology, 
>         Brisbane-4000, Australia.
>     +41434177254
> 
> 
> On Wed, May 22, 2019 at 5:36 PM Chintan Advani <chintanadvani at gmail.com <mailto:chintanadvani at gmail.com>> wrote:
> Hi Christoph, 
> 
> Thanks alot for replying and I am using QGIS 3.6 Noosa. I am using OSM line (linestring) as the network layer and a few set of data points as an another shape file( attached with the mail). I have various vehicles with their co-ordinates in this sheet. The log message says to check the qgis log for further information but cannot find it. I am using offline map matching with version 2.2.1. I am attaching the network file and csv file for your reference. Can you please help me resolving the issue.
>  osm line.dbf <https://drive.google.com/file/d/1yLXX2Mi4tevP2YawUDv1VPNqbw-yRv6W/view?usp=drive_web>
> Thanks and Regards,
> __________________________________________
> Advani Chintan Sanjeev
>         Research Scholar,
>         Civil Engineering and Build Environment,
>         Queensland University of Technology, 
>         Brisbane-4000, Australia.
>     +41434177254
> 
> 
> On Wed, May 22, 2019 at 4:35 PM Christoph Jung <jagodki.cj at gmail.com <mailto:jagodki.cj at gmail.com>> wrote:
> Hello Chintan,
> 
> Please provide more details about your problem. What did you do, what worked well, what did not worked as expected? Which version of the plugin and QGIS are you using? If the plugin throws an error, have a look into the QGIS-log. All exceptions of the plugin will be logged there. Give me as much as possible information, that I can reproduce your problem.
> 
> Sincerely,
> Chrsitoph
> 
> > Am 22.05.2019 um 03:28 schrieb Chintan <chintanadvani at gmail.com <mailto:chintanadvani at gmail.com>>:
> > 
> > Hey, I was looking to plot the trajectory in QGIS using your developed plugin
> > but I think there are some bugs and its not working, can you please help?
> > 
> > 
> > 
> > 
> > 
> > --
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