Weird Polyline Result

[camcima]

Issue

I'm using a local OSRM docker instance (osrm/osrm-backend:latest) with a uruguay-latest extract downloaded at Geofabrik to create a simple short roundtrip route but there's a weird deviation on the first leg of the route that throws it to a completely wrong path.

This is the route I should get (using OSRM demo site)

This is the route I'm getting.

Steps to reproduce

Please provide the steps required to reproduce your problem.

• osrm-backend version being used: osrm/osrm-backend:latest docker image (v5.25?)
• OSM extract that was processed: uruguay-latest.osm.pbf (Geofabrik)
• Processing commands (e.g. CH vs MLD processing): mld
• Server queries:

  curl 'http://localhost:5000/route/v1/driving/-56.187188,-34.891312;-56.199562,-34.905812;-56.187188,-34.891312?overview=full'

{"code":"Ok","routes":[{"geometry":"px}sEhb}uILi@DIFCn@XF@RHPq@?M@QAMEKGMKKIEKGm@U_@OwAi@[O]MKAK?I@GBMFKHIJKVUz@I`@]fBCR@RBLHRJPTPJDbA`@lAd@bA`@H@H@F?LCJGBAFK\\_@NOBMNAP?x@DR?TDNBpAf@LFzAl@fA`@|CnAfC`AlFtBnBt@l@TdBr@bAb@h@V\\NTN`@^VTHJFJBH@JBl@?JBH@BBBDBD@H?JAP?hBIbACTBZJbA^bE`B`A`@bCt@bExA^NNLpCjAHpCN~EN`FN~ELbF~AIFnA?LU?Q@y@BI@G@wAl@wAl@iBv@oB|@E@SHSw@}@uDc@UKUOiEM}EQcFM_FOcFMeEAWCg@A[cEeBWKw@WmBu@_EaBq@Ua@MeCaAoCgAmBu@mFuBiCcA}CmAsCgAOGaBq@UIkBu@HYJc@Gy@?M@QAMEKGMKKIEKGm@U_@OwAi@[O]MKAK?I@GBMFKHIJKVUz@I`@]fBCR@RBLHRJPTPJDbA`@lAd@bA`@H@H@F?LCJGBAFKTaASGq@WEGAKR}@","legs":[{"steps":[],"distance":2910.4,"duration":349.5,"summary":"","weight":349.5},{"steps":[],"distance":3035.5,"duration":351.8,"summary":"","weight":351.8}],"distance":5945.9,"duration":701.3,"weight_name":"routability","weight":701.3}],"waypoints":[{"hint":"kFUBgJJVAYBJAAAAMQAAAIAAAABfAAAAJIn0QeS0o0G32lNC-o0dQkkAAAAxAAAAgAAAAF8AAAA4AAAA86Wm_AOY6_3Mpqb80Jnr_QQA_wZ4IBDD","distance":54.854771,"name":"","location":[-56.187405,-34.891773]},{"hint":"2ioBgP___38JAAAAKgAAAA0AAAAAAAAAJlsVQTyNA0LQ6UhBAAAAAAkAAAAqAAAADQAAAAAAAAA4AAAAnXWm_CJh6_12dqb8LGHr_QEATxZ4IBDD","distance":19.859059,"name":"Ciudadela","location":[-56.199779,-34.905822]},{"hint":"kFUBgJJVAYBJAAAAMQAAAIAAAABfAAAAJIn0QeS0o0G32lNC-o0dQkkAAAAxAAAAgAAAAF8AAAA4AAAA86Wm_AOY6_3Mpqb80Jnr_QQA_wZ4IBDD","distance":54.854771,"name":"","location":[-56.187405,-34.891773]}]}

If you're reporting an issue with https://map.project-osrm.org, please provide a link to the problematic request.

Specifications

Please provide details of your development environment.

• Library/dependency versions: Docker
• Operating system: Docker
• Hardware: Docker

[danpat]

Make sure you are handling the escaping in the polyline string correctly - there are backticks and backslashes (\) that you need to be careful handled when you copy/paste the string. Your symptoms of the string becoming slightly offset at some point kind of points to this kind of error - polyline strings are delta encoded, and it seems likely you've dropped a character which messes up all the subsequent delta values.

In the image "this is the route I'm getting" - you didn't say how you actually generated that map. How did you take the string from the JSON response and pass it to something to render? I suspect the mistake is in that step.

[camcima]

Yes, I've copied and pasted the string from the json response to https://www.freemaptools.com/create-and-plot-encoded-polyline-on-map.htm. I've also tried Google's Polyline Utility (https://developers.google.com/maps/documentation/utilities/polylineutility) and it shows the same deviation.

[danpat]

You can't just copy the value from the JSON and expect it to work - it is a "JSON escaped string" - you need the unescaped string. It is a bit unfortunate that the \ character is a valid symbol in the polyline encoding character set.

You can use a tool like jq to extract and unescape the string, like this:

curl 'http://localhost:5000/route/v1/driving/-56.187188,-34.891312;-56.199562,-34.905812;-56.187188,-34.891312?overview=full' | jq -r .routes[0].geometry

alternatively, replace all the \\ with \ - those are the escape characters in JSON string encoding. If you do that, you'll see the polyline is correct:

[camcima]

You're absolutely right. I've just tried with a geojson output and it displays the route correctly. Thanks a lot for your prompt response @danpat!