QGIS – Troubleshooting Mapbox Vector Tile Display Issues Due to Unsupported Data Types

mapbox-vector-tileprotobufqgistippecanoe

I created a Mapbox Vector Tile collection in .mbtiles format using tippecanoe. Using the QGIS browser I can add the .mbtiles file as a layer and I see the data as expected, so I know the .mbtiles file is fine.

My application requires each of the vector tiles to be served separately via z/x/y URL paths, so I have to unpack the .mbtiles file.

I extracted all tiles with mb-util --image_format=pbf filename.mbtiles output_directory. This created the expected directory / file structure, e.g. 5/4/11.pbf.
I started a local HTTP server within output_directory and added the local URL to QGIS under "Vector Tiles" -> "New Generic Collection". Unfortunately QGIS does not render any vector tiles, even though it does appear to successfully retrieve data over HTTP. The QGIS network log shows many HTTP 200 "OK" responses from my local HTTP server and the correct Content-Length value, so I'm confident that QGIS is accessing the tiles. QGIS is not providing any feedback on what the problem could be, even in the Log Messages panel.

In an effort to debug the problem I tried using mvtview. mvtview crashes when I attempt to view a tile with mvtview output_directory/5/4/11.pbf. The error is thrown here within the pbf package and I think this means my vector tile has a field (presumably an attribute) with an unsupported data type. The logic within the skip function appears to move a pointer to the end of a field, but cannot determine how many bytes to jump for a field in my tile. The unsupported type is 3, which is missing from the list of supported types here. I'm having trouble figuring out what 3 might be.

I've removed all attributes except one from the source data, and that remaining attribute is type QString or String according to QGIS. I'm currently unsure how to debug the issue further.

Best Answer

With further research I discovered the error I received is often a sign that the tiles need to be decompressed before being read. I had not applied any compression, and my local HTTP server was not configured to compress tiles for transit, but tippecanoe applies compression by default. I addressed the issue by adding --no-tile-compression to my tippecanoe command.

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[GIS] TypeError: “unsupported operand type(s) for /: ‘int’ and ‘list'” in QGIS

As mentioned by Michael Stimson the error is because a list was used where a number was expected.

densidade_rios is returning the result of a division, hence areabh (which is the division's denominator) needs to be a value:

areabh = blayer.getValues('Area_km2')[0][0] # where 'blayer.fields()[0].name()' is the field name 'Area_km2'.

Another way of getting areabh would be:

areabh = [f['Area_km2'] for f in blayer.getFeatures()][0]

QGIS – How to Generate a Mapbox Vector Tile Correctly

After a few rounds of trial and error, I figured out a way to properly generate vector tiles. This is especially useful if you have no idea what the projection system of the shapefiles is.

Step 1: Convert the shapefiles from your source to a GeoJSON. In my case, I retrieved it from Postgres DB. It merges all the shapefiles to form one GeoJSON file

ogr2ogr -f GeoJSON output.geojson PG:'dbname=<> user=<> password=<> host=<>' -sql 'select * from <table_name>' -lco RFC7946=YES

Step 2: Use Tippecanoe to convert this GeoJSON to mbtiles. Please keep the names of the file consistent throughout [All files are named 'output' here and only the extension changes]

tippecanoe -o output.mbtiles -Z 0 -z 15 output.geojson

This step generated a .mbtiles file. Now these mbtiles need to be converted to a Vector tile folder structure

Step 3: Use ogr2ogr tool to convert mbtiles to MVT. [Do not use mbutil since it is not supported anymore and may cause issues]. Here 'data' is the name of my folder but you can name it anything else.

ogr2ogr -f MVT ./data output.mbtiles

Now you will have a folder structure that you can upload to S3. However, there are a few things you need to keep in mind.

All the .pbf files that get generated need to set Content-Encoding: gzip for all the files except for the metadata.json file. You can set it manually from the AWS console or add it to your copy command.

aws s3 cp --metadata-directive REPLACE --content-encoding 'gzip' <SOURCE_PATH> <DESTINATION_PATH> --recursive --exclude 'metadata.json'

To render the vector tiles in your code, follow this format First add the S3 location as source

 map.addSource("vector-tile-test", {
 "type": "vector",
 "tiles": [
   "https://<your-s3-url>{z}/{x}/{y}.pbf"
 ],
 "maxzoom": 10
});

Then add the Vector tile layer. Note that source-layer value is 'output'. You can find the value of your source layer in metadata.json file as well.

map.addLayer({
    "id": "vector-tile-layer",
    "type": "fill",
    "source": "vector-tile-test",
    "source-layer": "output",
    "paint": {
        "fill-color": "#FF0000",
        "fill-opacity": 1.0,
    }
  });

This should generate your vector tiles and render them accurately.

Best Answer

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[GIS] TypeError: “unsupported operand type(s) for /: ‘int’ and ‘list'” in QGIS

QGIS – How to Generate a Mapbox Vector Tile Correctly

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