Best way to get coordinates of each node of a way?

Question

I'm am on a project that would like to obtain the GPS boundaries of objects/locations of interest in JSON format. We have found it possible to make a single API call to http://overpass-api.de/api/interpreter? to get a list of ways with node ID's. We then found that we could traverse the list and make another API call to https://api.openstreetmap.org/api/0.6/node/{nodeID}.json to obtain the individual node coordinates. Is there a more efficient process in retrieving this information as some ways could have up to 2000 nodes? Thanks for the information in advance!

Accepted Answer

2

Overpass-API has functionality to retrieve the nodes: https://wiki.openstreetmap.org/wiki/Overpass_API/Overpass_QL#Recurse_down_.28.3E.29

Typically you'd do something like

(way[...];
>;
);
out;

where the way[...]; is what you are doing to find the ways, and then >; adds the results to the union.

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answered 27 Jan '21, 02:06

maxerickson
12.7k●10●83●176
accept rate: 32%

Thank you, I was not aware of the recurse down feature.

(19 Feb '21, 02:57) nonProfitDev...

Have you looked at my answer, which shows better ways to get just the coordinates, if you're not interested in the node objects?

(19 Feb '21, 07:00) ikonor

Answer 2

0

You can retrieve a way and all of its nodes directly from the OSM API:

https://www.openstreetmap.org/api/0.6/way/1010/full

However keep in mind that this API is primarily for editing OSM data. Don't perform bulk requests against it.

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answered 27 Jan '21, 08:41

scai ♦
33.3k●21●309●459
accept rate: 23%

Answer 3

Beside recurse down (>), Overpass API offers additional options to resolve the node references of a way and to get the coordinates of the nodes:

out geom

Using out geom output:

[out:json];
way(95777558);
out geom;

writes the node coordinates to an additional geometry property in the way object:

"geometry": [
  { "lat": 44.4198143, "lon": 38.2052864 },
  { "lat": 44.4196878, "lon": 38.2052733 },
  { "lat": 44.4195565, "lon": 38.2052576 }
],

No need to include the full node objects in the result.

GeoJSON format

Using the Geometry operator geom() in a convert statement:

[out:json];
way(95777558);
convert item ::=::,::geom=geom(),_osm_type=type();
out geom;

http://overpass-turbo.eu/s/12TN (GeoJSON map display not supported by Overpass Turbo)
http://overpass-api.de/api/interpreter?data=...

converts the way object into a derived object with the given properties and writes the coordinates into the geometry property in the GeoJSON format:

"geometry": {
  "type": "LineString",
  "coordinates": [
    [38.2052864, 44.4198143],
    [38.2052733, 44.4196878],
    [38.2052576, 44.4195565]
  ]
},

Best way to get coordinates of each node of a way?

out geom

GeoJSON format

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