Convert Mapbox Vector Tiles to Longitude and Latitude

Question

I am using Mapbox's QA Tiles and Python to access OSM data. While the tile-based approach is very handy I got stuck with how the geometry is saved. Apparently, coordinates are optimized for Mapbox's rendering needs and are 'vector tile grid coordinates'. To my surprise, I can't find any reference that would help me to understand what they actually did.

In my case, I want to check if a location (as latitude and longitude) are within an OSM area (Polygon or Multipolygon). This is what I got from the QA tile:

{ "osm": { "version": 2, "features": [ { "geometry": { "type": "Point", "coordinates": [ 95810, 1041260 ] }, "type": 1, "properties": { "@uid": 144382, "backrest": "yes", "@id": 3072121792, "@timestamp": 1410453825, "@changeset": 25372130, "amenity": "bench", "@user": "SHuehne", "@version": 1, "@type": "node" }, "id": 0 }, … ] "extent": 1048576 } }

This is the example node in OSM, the QA tile is z=12, x=2163, y=1435.

Answer 1

I kept on reading and I guess I found the answer myself. I won't delete the answer, maybe someone else will bump into the same problem.

mapbox-vector-tile is the library I use and its documentation explains how they transformation are done: https://github.com/tilezen/mapbox-vector-tile#coordinate-transformations-for-encoding

Answer 2

@linqu's answer the best for Python as per your question.

A JS implementation which extracts the VT geometry as GeoJSON is at https://github.com/mapbox/vector-tile-js/blob/master/lib/vectortilefeature.js#L129

Other JS tools which can help:

• https://github.com/mapbox/vector-tile-js
• https://github.com/mapbox/vt2geojson