{"action":"created","issue":{"url":"https://api.github.com/repos/mapbox/tippecanoe/issues/562","repository_url":"https://api.github.com/repos/mapbox/tippecanoe","labels_url":"https://api.github.com/repos/mapbox/tippecanoe/issues/562/labels{/name}","comments_url":"https://api.github.com/repos/mapbox/tippecanoe/issues/562/comments","events_url":"https://api.github.com/repos/mapbox/tippecanoe/issues/562/events","html_url":"https://github.com/mapbox/tippecanoe/issues/562","id":319154307,"node_id":"MDU6SXNzdWUzMTkxNTQzMDc=","number":562,"title":"Gaps and overlaps in tiles on high zoom with -zg","user":{"login":"jdeboer-geoplan","id":23341752,"node_id":"MDQ6VXNlcjIzMzQxNzUy","avatar_url":"https://avatars2.githubusercontent.com/u/23341752?v=4","gravatar_id":"","url":"https://api.github.com/users/jdeboer-geoplan","html_url":"https://github.com/jdeboer-geoplan","followers_url":"https://api.github.com/users/jdeboer-geoplan/followers","following_url":"https://api.github.com/users/jdeboer-geoplan/following{/other_user}","gists_url":"https://api.github.com/users/jdeboer-geoplan/gists{/gist_id}","starred_url":"https://api.github.com/users/jdeboer-geoplan/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jdeboer-geoplan/subscriptions","organizations_url":"https://api.github.com/users/jdeboer-geoplan/orgs","repos_url":"https://api.github.com/users/jdeboer-geoplan/repos","events_url":"https://api.github.com/users/jdeboer-geoplan/events{/privacy}","received_events_url":"https://api.github.com/users/jdeboer-geoplan/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":30,"created_at":"2018-05-01T09:23:52Z","updated_at":"2018-06-20T21:50:26Z","closed_at":null,"author_association":"NONE","body":"Hi,  I've got a small problem with the -zg option, there might be a flag option I'm missing that would sort it out.  When I run with -zg it guesses that I want to go down to z8\r\n\r\nChoosing a maxzoom of -z6 for features about 5147 feet (1569 meters) apart\r\nChoosing a maxzoom of -z8 for resolution of about 1281 feet (390 meters) within features\r\n\r\nHowever when I zoom in to level 14 it has lots of holes and overlaps, if I generate it to level 14 it looks fine all the way to 20.\r\n\r\nOutput\r\n![image](https://user-images.githubusercontent.com/23341752/39467794-c58917a4-4d27-11e8-8f5a-ef9e73314e80.png)\r\n\r\nIf I use -ab the results are much better but still not perfect:\r\nOutput\r\n![image](https://user-images.githubusercontent.com/23341752/39467906-5fb40da2-4d28-11e8-8877-c76d3af47236.png)\r\n\r\nI'd hoped -pS might help but although the tile file is slightly bigger I can't see any difference in output.\r\n\r\nI can provide the geoJSON but I feel this must be a known problem and I'm just failing to find the right flag combo to sort it out.  Obviously I can get my tiles by generating all the way to z14 but I'm attracted to the much faster creation and smaller tile file size of only going to z8 if that's possible with my data.\r\n\r\nThanks\r\n"},"comment":{"url":"https://api.github.com/repos/mapbox/tippecanoe/issues/comments/398909067","html_url":"https://github.com/mapbox/tippecanoe/issues/562#issuecomment-398909067","issue_url":"https://api.github.com/repos/mapbox/tippecanoe/issues/562","id":398909067,"node_id":"MDEyOklzc3VlQ29tbWVudDM5ODkwOTA2Nw==","user":{"login":"ericfischer","id":1951835,"node_id":"MDQ6VXNlcjE5NTE4MzU=","avatar_url":"https://avatars1.githubusercontent.com/u/1951835?v=4","gravatar_id":"","url":"https://api.github.com/users/ericfischer","html_url":"https://github.com/ericfischer","followers_url":"https://api.github.com/users/ericfischer/followers","following_url":"https://api.github.com/users/ericfischer/following{/other_user}","gists_url":"https://api.github.com/users/ericfischer/gists{/gist_id}","starred_url":"https://api.github.com/users/ericfischer/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/ericfischer/subscriptions","organizations_url":"https://api.github.com/users/ericfischer/orgs","repos_url":"https://api.github.com/users/ericfischer/repos","events_url":"https://api.github.com/users/ericfischer/events{/privacy}","received_events_url":"https://api.github.com/users/ericfischer/received_events","type":"User","site_admin":false},"created_at":"2018-06-20T21:50:26Z","updated_at":"2018-06-20T21:50:26Z","author_association":"CONTRIBUTOR","body":"For my reference: the area in question is near 9.5/43.9681/-112.0949.\r\n\r\nI'm pretty sure the geometric errors are in your original data, which is only given to 3 decimal digits of precision (about 350 feet). If I convert your polygon rings to individual LineStrings and tile them considerably deeper than the display resolution, it is clear that the contours do not match up in many places.\r\n\r\n![screen shot 2018-06-20 at 2 45 16 pm](https://user-images.githubusercontent.com/1951835/41686394-c0d8b870-7498-11e8-8c1a-4aa9c9113357.png)\r\n\r\nIf you are not seeing overlaps in mapshaper, it is because it is drawing the shapes opaquely rather than with partial transparency, which hides the overlaps.\r\n\r\nI think whatever process is creating these polygons is doing its own line simplification, and that to get the results you want you will need to stop it from simplifying or get it to use a higher precision during simplification."}}
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