PBF vector tile support

[stevage]

TileJSON doesn't seem to support Mapbox's own vector tiles spec. Am I misunderstanding something, or is this an omission?

I can see two ways to support it:

1. The data element should allow URLs that end in .pbf and return PBF files. But then, with the REQUIRED tiles attribute, it would be a bit awkward to conform to the spec for a purely vector source...
2. The tiles element should allow URLs that end in .pbf and return PBF files.

Either way I guess the scope of the spec is changing, since presumably it was originally envisaged that this was strictly for raster tiles and here it is being used for vector data...

[yhahn]

@stevage we have been going with option 2 (specifiying vector.pbf URLs in the tiles key of tilejson). Is there something in the tilejson spec you're seeing that implies that the tiles key should be limited to a particular format?

[stevage]

Ah thanks. No, there's nothing that says explicitly that tiles can only be .png. (There's also nothing that says that other formats are ok, or that the URL should determine the format.)

However, when I tried using .pbf tiles with Mapbox Studio and it didn't work I concluded (wrongly) that using .pbf files wasn't ok. Which is perhaps another way of saying that the spec isn't totally clear.

[stevage]

Also, it does seem that there is an ambiguity if you're serving GeoJSON tiles. A quick reading of the spec would suggest using the data field, but then you'd run into the REQUIRED tiles field.

Another ambiguity is in the "All endpoints MUST return the same content for the same URL" clause. It's not totally clear to me whether having a .pbf and .geojson endpoint would satisfy that clause or not (it would be the same "content", but in two different formats.) I imagine it probably wouldn't. (It's also slightly wrong to say "for the same URL", because by definition different endpoints have different URLs...that confused me a bit at first, thinking it meant that each endpoint just had to be consistent about how it responded to a given request...)

[rochoa]

What if I want to support both PNG and PBF tiles?

I could use tiles for the PNG URLs and data for the PBF URLs, however, the spec for data is An array of data files in GeoJSON format..

[mapsam]

Hey y’all, this could use some improved language in the specification to make it clear where to specify the tile format. We’ll plan on clearing this up in the upcoming v3 specification, with an eye towards the tiles, and data. We'll comment back here when there's something to review!