[gdal-dev] Vector Tiles in OGR

Tue Jan 5 17:35:31 PST 2016

I’ve commented on the MBTiles discussion [1] and suggested to make a change towards GeoPackage. There are in my opinion some reasons why it should rather be avoided to implement something towards MapBox’ current Tile spec or MBTiles, or any of the current vector tile formats in general:

  *   Interoperability. Besides the need to define a custom extension for MapBox Vector tiles within a GPKG container (because vector tiles are not part of the spec) a standard based format with proper data field definitions would increase operability a lot.
  *   Conceptually. In my opinion, it should be avoided to mix rendering optimized data and geometry data. These should be separate concerns, but my understanding is that all vector tiles are currently optimized for rendering only, and not concepted as general purpose containers to convert to and from without anything breaking in practice. They are bound to a particular projection (in MapBox’ case always Web Mercator) and geometries cannot be exactly reconstructed after they’ve been tile-cut at the projection specific tile bounds.
  *   Tiling. When going for vector „tiles“ there should be no more need to stick to a certain projection. It should be possible to use unprojected data, and do the projection either in realtime or as part of a post processing step. In any case, the limitation to use just one projection (Web Mercator) may not be acceptable for general purpose application. As Blake said, merging features is a non-trivial problem. But once this is solved (maybe as part of a new vector tile spec), there is from a technical perspective no more need to produce tiles for rendering other than for performance reasons. Vector data can be pushed into a scene graph that contains all currently visible geometries. Tile data would still be sliced loosely in accordance to tile sizes and zoom levels, but not strictly so, and without need to produce projected data. I’m thinking of using an adaptation of the MODIS Grid [2] as tile storage (to store WGS84 datum, and reconstruct „partially complete“ geometries reproject and reproject to Web Mercator or UTM at runtime).

I think it would be of great benefit if common containers like GPKG would be adopted by more vendors. So that in the end more tools could operate on a data set first, and this data set could then be brought into an optimized form for specific rendering needs (which could also be an extension to GPKG as mentioned).

Cheers
Ben

[1] https://github.com/mapbox/mapbox-gl-native/issues/3373
[2] http://modis-land.gsfc.nasa.gov/MODLAND_grid.html

Von: gdal-dev <gdal-dev-bounces at lists.osgeo.org<mailto:gdal-dev-bounces at lists.osgeo.org>> on behalf of Blake Thompson <flippmoke at gmail.com<mailto:flippmoke at gmail.com>>
Datum: Dienstag, 5. Januar 2016 um 22:12
An: Even Rouault <even.rouault at spatialys.com<mailto:even.rouault at spatialys.com>>, "fischer at mapbox.com<mailto:fischer at mapbox.com>" <fischer at mapbox.com<mailto:fischer at mapbox.com>>
Cc: "gdal-dev at lists.osgeo.org<mailto:gdal-dev at lists.osgeo.org>" <gdal-dev at lists.osgeo.org<mailto:gdal-dev at lists.osgeo.org>>
Betreff: Re: [gdal-dev] Vector Tiles in OGR

Even,

He is correct that MBTiles can store vector tiles. I know this is done in https://github.com/mapbox/tippecanoe . I believe there is talk about updating the MBTiles Spec as well.

Thanks,

Blake Thompson

On Tue, Jan 5, 2016 at 2:21 PM, Even Rouault <even.rouault at spatialys.com<mailto:even.rouault at spatialys.com>> wrote:
Le mardi 05 janvier 2016 19:33:32, Petr Pridal a écrit :
> Hi,
>
> Is anybody working on an OGR driver for mapbox-like vector tiles (PBF
> blobs) stored in MBTiles or downloaded from a url via curl?

Hi Petr,

I was involved in discussions a few months ago where Mapbox Vector Tiles
read/write support would have been part of a larger project, but I'm not sure
if/when this will come true.

I see you mention MVT in MBTiles. Is it a recognized practice ? I don't see
mention of that neither in the MVT spec ( https://github.com/mapbox/vector-
tile-spec/tree/master/2.0 ) nor the MBTiles one (
https://github.com/mapbox/mbtiles-spec/blob/master/1.2/spec.md ), although I
guess it is just a matter of storing a MVT blob in the tile_data column.

Even

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