Filter raises 'Polygon begins with an inner ring' without changing that data

[omrivolk]

I used tippecane with -C 'python myfilter.pyo' and got an error

Polygon begins with an inner ring

So I reduced the filter to just

-C 'cat'

And I get the same error

But removing the -C script completely doesn't raise an error

My full command:

tippecanoe -n "routing tileset" \
  -P -Z11 -z11 -D12 -d13 --no-feature-limit \
  -x OBJNAM -x FID -x water -x natural -x cc -x tile_x -x tile_y -x error \
  -o routing.mbtiles \
  -C 'cat' \
  --clip-bounding-box=-68.500000,44.583290,-66.500000,46.583290 \
  -Losmwt2:<(cat ./dist/osm/geojson/osm.water.geojsonseq;) 

So it seems like the filter raises 'Polygon begins with an inner ring' without changing that data

[e-n-f]

Thanks for the report. Can you share your data file so I can try to reproduce the problem?

[omrivolk]

https://www.dropbox.com/s/ufo6p6vmtta5kh9/osm.water.geojsonseq.zip?dl=0

It's an osmium export of some water polygons from: us-northeast-latest.osm.pbf

[e-n-f]

Thanks! I'll take a look

[omrivolk]

I've solved it for now by using a -c postfilter instead, for my use case it does what I want and does not raise an error.

[e-n-f]

Great, I'm glad you were able to get it working!

[jliebrand]

I'd still be interested to know if a fix could be applied so we can run the script on -C if possible

[mkieselmann]

I got the same error when using a prefilter. The error seems to occur on a polygon which is in parts a straight line and contains the same coordinate twice. However, the original input Polygon (JSON input for tippecanoe) is valid and has no straight lines. The malformed polygon seems to be created after converting MVT back to rings in json_writer.cpp. The MVT representation has been scaled to tile resolution before, which is probably the cause for malforming.

The error occurs for zoom 8 with the following command: tippecanoe -z 9 -Z 8 -S 10 ...

Increasing detail fixes the problem: tippecanoe -z 9 -Z 8 -S 10 -d 19 ...

Any ideas how prevent the prefilter from failing at low zoom levels?

Malformed Polygon as it should be written to stdin before the prefilter.

{
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              12.683372,
              52.570299
            ],
            [
              12.683544,
              52.570925
            ],
            [
              12.683716,
              52.571238
            ],
            [
              12.683544,
              52.570925
            ],
            [
              12.683372,
              52.570403
            ],
            [
              12.683372,
              52.570299
            ]
          ]
        ]
      }

Original Polygon from JSON source:

    {
      "type": "Feature",
      "properties": {},
      "geometry": {
        "type": "Polygon",
        "coordinates": [
          [
            [
              12.68339599,
              52.5702426
            ],
            [
              12.68343278,
              52.57022606
            ],
            [
              12.68349856,
              52.57039534
            ],
            [
              12.6836822,
              52.57086776
            ],
            [
              12.68382317,
              52.57113737
            ],
            [
              12.68415019,
              52.57176286
            ],
            [
              12.68419578,
              52.57186959
            ],
            [
              12.68426361,
              52.57202743
            ],
            [
              12.68421513,
              52.5719956
            ],
            [
              12.68410935,
              52.57177365
            ],
            [
              12.68363914,
              52.57087399
            ],
            [
              12.68339599,
              52.5702426
            ]
          ]
        ]
      }
    }