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Summary of common issues about fmm #138
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Trajectories not matched.In case that a trajectory cannot be matched to the road network. The reason could be
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Weird map matching resultIf you saw some weird matching result, where the matched trajectory significantly deviate from the original one, the reasons could be
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Configurations setting
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Be careful with unit of configurationsIf your GPS data is in degrees e.g., latitude and longitude, your network should also be in degree. The configurations are also defined in degrees:
Extremely large UBODT or it takes long time to generate UBODT.
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How about the unit of the output? For example, the error and the offset, do they also need to multiply the 1.132e5 to get the unit in meters? |
All units are the same as GPS data and network data. |
I am getting the following warning in most of the trajectories. [warning] [fmm_algorithm.cpp:289] Traj 0 unmatched as points 83 and 84 not connected which leads to no map matching to the given trajectory. I am using https://github.com/cyang-kth/osm_mapmatching link for network generation. Is it due to data quality? Please let me know. |
I am having the same problem with a gps dataset [1] getting eros like
in almost all cases. This warning returns empty results, i.e. not any matching is performed. I have tried multiple parameters like
but the warning persists. In addition, for the record, my example is based on [2]. In case you want to see the data, I am attaching a few trajectories taken from [1]. Could you please provide some suggestions on how to overcome this problem? Any help is highly appreciated! [1] https://www.kaggle.com/c/pkdd-15-predict-taxi-service-trajectory-i [2] https://github.com/cyang-kth/osm_mapmatching 1372690597620000513.txt |
Try to smooth your trajectory before performing map matching, it might help. There is also a parameter called |
This page contains a summary of common issues in using fmm.
Firstly, make sure you pull the latest version of the program.
Road network
Road network should be downloaded following the script at https://github.com/cyang-kth/osm_mapmatching.
The original network downloaded from osmnx will not work for fmm because
If you use your own network, make sure your network has
The network downloaded from https://github.com/cyang-kth/osm_mapmatching generally satisfies the above requirement.
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