Permanent ID for OSM
This is an unofficial proposal for a "permanent ID" (osm_pid) for OpenStreetMap (OSM). See here for a more well known place for discussions.
Goals and Requirements
The goal is to get an opaque (eventually fixed) length ASCII string for an OSM id.
That are the design considerations:
- The OSM id alone is not stable enough (as probably most agree); and it can represent many concepts (and that's by design in OSM).
- The version no. of the object is needed which makes clear which tags are (or have been) referred to.
- Coordinates are needed, because a change of the way and area geometries does not increment the version number.
Status of OSM id
One can use OSM id nevertheless (at own risk)! Many variants are known:
As is with OSM id (bigint) and a code for Node, Way, Relation in front. Currently many applications depend on plain osm_id, eventually preceeded by node,way,relation (or N/W/R), like theses web applications:
- The main OSM web page: Example Denner Hombrechtikon https://www.openstreetmap.org/node/6313169265
- Qwant Maps: Example Denner Hombrechtikon https://www.qwant.com/maps/place/osm:node:6313169265@Denner#map=18.00/47.2519793/8.7681836
- Castle Map: Example Schloss Rapperswil https://castle-map.infs.ch/#46.805,8.205,8z,W417258377
Another usage of osm_id is to convert it to a single big integer: It's possible to encode the type (Node, Way, Relation) into the OSM id as a single integer (64 bit): osm_id = <node id> × 10 (eg. 123 → 1230), osm_id = (<way id> × 10) + 1 (eg. 123 → 1231), osm_id (<relation id> × 10) + 4 (eg. 123 → 1234). (Source: Mapbox, see [1]). Example: "Schloss Kyburg" is a relation with id 1169711, so it becomes 11697114.
osm_id*10 -- Node osm_id*10+4 -- Relation osm_id*10+1 -- Way
Format of OSM Permanent ID
A stable Permanent ID could have the following form (variable length to a maximum of currently 35 chars):
[N|W|R]<osm_id>#<version>[+|-]<lon>[+|-]<lat>
where:
- N,W,R stands for Node, Way, or Relation.
- osm_id an unsigned big integer ("digits").
- version is an unsigned integer with a hash in front.
- coordinates (lat/lon) are signed floats (always showing the +/- sign), with a maximum of 6 digits. In case of a line (linestring) or an area/relation (polygon) geometries the coordinates taken into account are the lat/lon minimum of the geometry.
Example: "Schloss Kyburg" (Castle Kyburg) has relation 1169711, version #5 at coordinates 47.4584, 8.74343 which becomes following Permanent ID:
osm_pid = R1169711#5+47.4584+8.74343
OSM Permanent ID Service
In order to be really useful, a service should be implemented, which returns most recent object given a possibly old Permanent ID if an object has been changed; thus having another Permanent ID where any of it's parts may have changed (most probably just the version no.). Such a service must have access to the fully planet including the history and it must be reliable and responsive.
Alternatives
See https://wiki.openstreetmap.org/wiki/Permanent_ID for a more official state of discussions.
'geo' URI as OSM Permanent ID
Use URI Scheme "Uniform Resource Identifier for Geographic Locations " ('geo' URI).
For a promising implementation see Mangrove.reviews.
Example: Supermarket Denner Partner, Hombrechtikon, https://www.openstreetmap.org/node/6313169265
OpenLR
OpenLR (Location Referencing) - a free spec. by TomTom for linear geometries like streets [2].