Point should not be "coordinates": [[lon, lat]], but [lon, lat] when setting "geometry=geojson"

[kkdd]

Hello,
At present, a query withgeometry=geojson results in:

$ curl "http://localhost:5000/route/v1/driving/133.540336,33.558187;133.540937,33.55841?steps=true&geometries=geojson" | jq -c '.routes[0].legs[].steps[].geometry | select(.type == "Point")'

{"type":"Point","coordinates":[[133.540906,33.558277]]}

But a correct geojson should be the following:

{"type": "Point", "coordinates": [133.540906, 33.558277]}
(or {"type": "MultiPoint", "coordinates": [[133.540906, 33.558277]]}).

[daniel-j-h]

You're right, quoting the spec:

2.1.2. Point
For type "Point", the "coordinates" member must be a single position.

2.1.3. MultiPoint
For type "MultiPoint", the "coordinates" member must be an array of positions.

and for Position:

2.1.1. Positions

A position is the fundamental geometry construct. The "coordinates" member of a geometry object is composed of one position (in the case of a Point geometry), an array of positions (LineString or MultiPoint geometries), an array of arrays of positions (Polygons, MultiLineStrings), or a multidimensional array of positions (MultiPolygon).

A position is represented by an array of numbers. There must be at least two elements, and may be more. The order of elements must follow x, y, z order (easting, northing, altitude for coordinates in a projected coordinate reference system, or longitude, latitude, altitude for coordinates in a geographic coordinate reference system). Any number of additional elements are allowed -- interpretation and meaning of additional elements is beyond the scope of this specification.

[TheMarex]

Urg yeah this is an API bug, fixing this would be a breaking API change though.

What would work is not not emit Point at all anymore but only LineString, but maybe with the same coordinate twice. Client code already needs to handle both cases, we would just not emit one of them anymore. Always emitting LineString might also be more consistent with the idea of step geometries.

[daniel-j-h]

For the record: #3426 fixed this by no longer emitting a Point in the single coordinate case. Instead we now always emit a LineString with the single coordinate duplicated. Backwards compatible.

Thanks for reporting and sorry for not noticing this edge case earlier.

[kkdd]

In a geojson, "LineString" should have two or more coordinates. See a pull request of "Adhere to GeoJSON spec by not return invalid LineStrings #2286" (Project-OSRM/osrm-backend).

[daniel-j-h]

Yes now a LineString has two coordinates if the geometry would have been a Point.

Before: Point coord
After:  LineString [coord, coord]

[TheMarex]

Yeah the original "fix" was a bad call on my side. LineString makes much more sense, as for these segments the start and endpoint coincide (zero length segments, such as the last segment of a route that marks the Arrive instruction.)