Wednesday, February 20, 2019

The Vector Tiles Pilot

Last year, I posted regarding vector tiles. I am pleased to announce that I have much more to report on this front. For the last six months, OGC has been sponsoring the Vector Tiles Pilot (VTP). The purpose of the VTP was to investigate how vector tiles (or tiled feature data, if you will) in the Mapbox Vector Tiles (MVT) and GeoJSON formats can be supported through the OGC standards baseline, particularly Web Feature Server (WFS), Web Map Tile Server (WMTS), and GeoPackage (GPKG). 

The initial effort concluded late last year and culminated in some videos and the following Engineering Reports (ERs):
Following the completion of the VTP, the sponsors funded an extension to the pilot (the Vector Tiles Pilot Extension or VTPExt) to take a closer look at styling of the ensuing feature data using the Mapbox Styles and Styled Layer Descriptor (SLD) encodings. This effort concluded last week and the resulting videos have been posted to YouTube. The ER is under review now (OGC members can access the current draft) and should be published in the next month or two.

From the GeoPackage perspective, the Vector Tiles Pilot allowed us to try out a series of GeoPackage Extensions:
  • Tiled Feature Data: allowing tiled feature to be stored using the tiles mechanism
  • Mapbox Vector Tiles: allowing tiles to contain MVT
  • GeoJSON Vector Tiles: allowing tiles to contain GeoJSON
  • Styles: allowing styles documents (e.g., Mapbox Styles, SLD, or others) to be stored in a way that is loosely coupled with feature data (tiled or otherwise)
  • OWS Context: allowing for OWS Context information to be stored (while we have an agreement in principle here, we did not have time to test it out)
  • Vector Tiles Attributes: allowing for attributes to be stored in attributes tables instead of in the vector tiles to support better querying (this topic is very complex and we did not actually reach a consensus here)
While these extensions were introduced in the ER linked above, they were further refined during the VTPExt. It is on my TODO list to add them to the GeoPackage Extensions Page. The next step is to present this information to the GeoPackage Standards Working Group (SWG) and to propose the extensions as candidate standards. I believe we have a clear use case and a sound technical approach. If the SWG agrees and there is a commitment to implementation, we may have an adopted standard later this year.

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