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Sequence is broken for submitted track at time step 0


#1

Hello everybody,

I’m new to Graphhopper. I’ve been trying to run map matching tests within the core project for different areas. I tried to run the algorithm on two maps from http://download.geofabrik.de, Bremen and Uruguay, and both of those tests returned an error message similar to this:

[main] ERROR com.graphhopper.matching.MapMatchingMain - Problem with file .\matching-core\src\test\resources\uruguay.gpx Error: Sequence is broken for submitted track at time step 0 (1561 points). observation:-30.78149,-57.708054,NaN, 1523649713000, 0 candidates: []. If a match is expected consider increasing max_visited_nodes.
java.lang.IllegalArgumentException: Sequence is broken for submitted track at time step 0 (1561 points). observation:-30.78149,-57.708054,NaN, 1523649713000, 0 candidates: []. If a match is expected consider increasing max_visited_nodes.
at com.graphhopper.matching.MapMatching.computeViterbiSequence(MapMatching.java:443)
at com.graphhopper.matching.MapMatching.doWork(MapMatching.java:239)
at com.graphhopper.matching.MapMatchingMain.start(MapMatchingMain.java:114)
at com.graphhopper.matching.MapMatchingMain.main(MapMatchingMain.java:44)

I’m generating the .gpx file via the Graphhopper web application, and then running the map matching algorithm from command line on Babun. This procedure has worked for other maps from geofabrik such as Leipzig and Saarland. If somebody could spare any insight as to why this is the case I would be very grateful.

Many thanks


#2

Hard to tell without the file. Did you make sure that you are actually running it against the correct map?


#3

Hi, would it be possible to elaborate on the causes of the “sequence is broken” error? I’m experimenting with map-matching against different GIS layers of roads and see it quite often.

Is it caused by not having an underlying map that allows for a route between two points in your input sequence (allowing for a bit of fuzziness due to the GPS accuracy variable)?

In some of the comments, it’s been suggested to play around with “hopper.setMinNetworkSize(200,200);” but I can’t find documentation on this function and it’s variables - the “doWork()” function implies they have to be non-zero, but I’m scratching my head as to whether it’s better to increase or decrease these values.

Cheers,
Pete