Map matching: matched_points are missing in trace_attributes pbf response (different set of properties in pbf and json)

[NorekZ]

Hello there,

I am struggling with a issue coming from the fact, that Valhalla json and pbf trace_attributes responses have very different model.

My scenario is the following: I need to compute average speed for all edges returned by trace_attributes based on my input points (coordinate+timestamp). So for each segment between two input points I need to break down the route to the corresponding (matched) edges. Additionally, I need to consider edge costs when breaking down.

At first, I went the PBF route because of convenience. It gave me edge costs (not seconds):

{
    "trip": {
        "routes": [
            {
                "legs": [
                    {
                        .....
                        "node": [
                            {
                                ......
                                "cost": {
                                    "elapsedCost": {
                                        "seconds": 13,
                                        "cost": 5.293943881988525
                                    },
                                    "transitionCost": {
                                        "seconds": 2.2084739208221436,
                                        "cost": 8
                                    }
                                }
                            }
                    }
                ]
            }
        ]
    }
}

Unfortunatelly, the second part I need for the computation (matched_points) is missing in PBF.

I realized that in JSON response, there are matched_points, but edge costs are missing.

Would be possible to include matched_points in the PBF response?

Shouldn't be those response formats more consistent/similar to each other? It's just format...

Thank you guys for all the work. It's a great project!

Norek

[nilsnolde]

we use pbf for interprocess communication between the various valhalla modules and we actually just convert JSON from the pbf which we already have anyways. however, some stuff never made it into pbf and seems you hit one of the major ones. actually map matching doesn't even have its own pbf section, we re-use the routing stuff here too and add the matched_points (+ some other things e.g. the confidences scores) to the JSON based on the meili results.

I think by and large we're fairly consistent with pbf & json, but yeah, some things are lacking and need to be amended. for your particular case would it be enough to have the elapsed_cost in the JSON response? that'd be super quick to add, just add a writer("elapsed_cost", node.cost().elapsed_cost().cost()); here: https://github.com/valhalla/valhalla/blob/master/src/tyr/trace_serializer.cc#L307-L311

however, translating the meili results to pbf is a bit bigger..

[NorekZ]

Thank you for the quick response.

I made the suggested change is the linked PR.

Although it's much less convenient for me, at least it enables my whole use case.