Vector Tiles Reader QGIS Plugin: Unterschied zwischen den Versionen

Version vom 17. Januar 2017, 01:44 Uhr

QGIS-Plugin Vector Tiles Reader - This Python plugin reads Mapbox Vector Tiles (MVT) from a local MBTiles file and loads them into a vector layer that is rendered by QGIS and it's (default) styling.

• A project by Geometa Lab HSR
• Project Lead: Stefan Keller
• Authors/Developers: see Github

 >> This is experimental work in progress! Expected an early release as QGIS plugin around 2nd quarter of 2017 << 

Important websites:

• Source Code on Github: https://github.com/geometalab/Vector-Tiles-Reader-QGIS-Plugin
• QGIS plugin directory: http://plugins.qgis.org/vector_tiles_reader (tba.)

About

About Vector Tiles: Though this is a vector representation, Vector Tiles are rather specific data targeted to visualization and thus not fully comparable to generic geospatial vector data formats. Because of many optimization issues Vector Tiles are lossy in many respect: Coordinates are converted to integers and thus loose precision, features are filtered at certain zoom levels and geometries like roads are simplified. Moreover they are "overzoomed" which means that they often borrow data from upper zoom levels.

Available data sources (MBTiles):

• Download MBTiles (compatible to "Mapbox Streets v7") from OSM2VectorTiles project (see also city extracts).
• There's a possibility to download single tiles from online resources, like "Mapbox Streets v7" (tbd.)

Data model documentation:

• Data model of OSM2VectorTiles.
• Data model of "Mapbox Streets v7".

Available styles:

• As of now, there is no QGIS styling available for a vector tiles product. See data model documentation above to help yourself.

Known Limitations

Limitations in general:

• This plugin is only tested on reading MBTiles containing Vector Tiles according to Mapbox Vector Tile Specification 2.1.
• CRS is always EPSG:3857 Web-Mercator. Though Vector Tiles are in principle not bound to a coordinate reference system (CRS), currently it's only possible to handle Vector Tiles in Web-Mercator EPSG:3857.
• There's no styling attached to MBTiles nor to Vector Tiles.

Limitations of current plugin:

• Only tested on Linux and QGIS 2.14 (IMPORTANT). This plugin is not working on Windows due to an issue in the Windows Python libraries in QGIS.
• MBTiles are read from maxzoom (e.g. 14). All data from levels above will be ignored except for empty tiles which are taken from maskLevel (e.g. 8).
• Is structured into "<<basename_mbiles>>_Point", "<<basename_mbiles>>_Linestrings", "<<basename_mbiles>>_Polygons". It's not not structured according to Vector Tile layers.
• Leaves Linestrings and Polygons cut into tiles at tile boundary; therefore does not handle handle a street across two or more as a single feature.
• Lines and polygons remain cut off at tile boundaries. They can't be selected and highlighted like the original, since they are not yet stitched together.
• Can't handle currently multipoint, multilinestring nor multipolygon.

Enhancements and Ideas

The plugin could read Vector Tiles directly from the web. But then - to behave similar to raster tiles - the problem of missing corresponding styling becomes even more prominent.

Installation and Source Code

Intall as local plugin (not yet in QGIS plugin repo -[Install from inside QGIS as Python plugin (Note: For plugin versions up to 0.9 you have to enable "experimental plugins")]-).

Ressources

• https://github.com/mapbox/awesome-vector-tiles