Is there anyway to stop tippecanoe from dropping polygons at low/mid level zooms while keeping within the 500kb per tile size limit of mapbox uploads for an mbtiles file? We are getting a lot of polygons being dropped. We are not sure what flags to use to make this possible.
This is the command line:
tippecanoe -o polys.mbtiles \
--coalesce-smallest-as-needed \
--coalesce-densest-as-needed \
--coalesce-fraction-as-needed \
--simplify-only-low-zooms \
--no-feature-limit \
--no-tile-size-limit \
--minimum-zoom=10 \
--maximum-zoom=20 \
--calculate-feature-density
Without --no-feature-limit --no-tile-size-limit, features get dropped.
There are lots of possible solutions to prevent small polygons being dropped, depending on what the cause of the dropping is.
Remove attributes you don't need, with --include
Use --detect-shared-borders to store polygons that touch each other more efficiently.
Use --simplification=10 or higher to reduce the precision of locations.
Use --drop-smallest-as-needed so that the polygons that are dropped are the smallest ones, not randomly chosen.
Add specific properties onto your GeoJSON objects to specify which ones should not appear at certain zooms
But ultimately, there is a tradeoff. You can't have infinite information within every tile, so you will have to choose what information you do want to keep.
Related
I'm using OpenMapTiles to download OSM data and create a mbtiles with mapbox vector tiles. This all works great, except I'm targeting an embedded platform.
At zoom level 14 with the default extent of 4096, a single tile can be over 1MB and cover an entire city. Not only is that a huge file to process for an embedded platform, it also means you're potentially sifting through every house in an entire city. I went as far as writing a streaming protobuf parser, but it takes 10 minutes to just parse such a file.
How can I generate mapbox vector tiles with a smaller extent?
I found there appears to be a parameter for it, but can't figure out where it actually gets used to generate tiles and how to modify it: https://github.com/openmaptiles/openmaptiles-tools/blob/4cc6e88dfdef83de69bd49845e0f23908d9edecc/openmaptiles/sqltomvt.py#L25
I'm not married to openmaptiles, but it's what I'm currently using to download and process openstreetmap data.
in case others need it, use https://github.com/mapbox/tilelive and specify maxzoom you want
bin/tilelive-copy --minzoom=0 --maxzoom=10 ~/Apps/tileserver/tiles/osm-2017-07-03-v3.6.1-planet.mbtiles ~/Apps/tileserver/tiles/small-osm-2017-07-03-v3.6.1-planet.mbtiles
I am generating a layer UK scale, it is composed for several polygons, the idea for the layer is to display it fully and then the user can zoom to most specific area. The main problem is because the number of polygons when I create the .mbtile it split some of the polygon at determined zooms.
I have tried with different options of tippecanoe like --not duplication extend zooms if still dropping ... but I couldn't nail whit the correct commands to make it work.
tippecanoe -zg --read-parallel -l $LAYER -o "$OUT_MBTILES" "$OUT_JSON" --coalesce-densest-as-needed --extend-zooms-if-still-dropping --no-duplication
I suspect this is somehow related to --no-duplication. Per the documentation:
--no-duplication: As with --no-clipping, each feature is included intact instead of cut to tile boundaries. In addition, it is included only in a single tile per zoom level rather than potentially in multiple copies. Clients of the tileset must check adjacent tiles (possibly some distance away) to ensure they have all features.
I'm not sure why you're using that option, but disable it if possible.
It's hard to be more specific without seeing your data and having a lot more information about what you're trying to achieve, zoom levels, attributes, data size etc.
I've created a base layer and 6 different overlay (Points of Interest) layers for a leaflet map.
The base layer of markers can appear on the map almost anywhere in the world, but I want the POI layers to appear only if they are in the same area (mapBounds) of the base layer. Probably the screen size.
All the data is pulled from a MySQL database and using Ajax I create the various sets of markers from two different tables, base and poi. This much is all done and working, you can see it at https://net-control.us/map2.php. The green and blue markers are from the base table, other markers are currently selected for view by clicking on the appropriate icon in the lower right. The only one active at the moment is 'Fire Station'. But if you zoom out far enough you will see additional fire stations in the Kansas City area, and in Florida. Those sets are not needed.
After the query runs I create a fitBounds variable of the base layer and another poiBounds for the poi layer. But I'm not sure I need the poiBounds. The number of base markers is generally less than 50 for the base query, but if all the poi markers are pulled world wide that number could be very large.
So I'm hoping someone can help me determine a best practice for this kind of scenario and maybe offer up an example of how it should be done. Should I...
1) Download all POIs and not worry about them appearing outside the base bounds layer? Should I inhibit them from showing in the javascript or in the SQL? How?
2) If I inhibit the unwanted points from SQL do I test one POI at a time to see if its included in the base bounds? How? Are there MySQL functions perhaps to work with this kind of data?
I'm fairly new at leaflet maps and would appreciate examples if appropriate.
2) If I inhibit the unwanted points from SQL do I test one POI at a time to see if its included in the base bounds? How? Are there MySQL functions perhaps to work with this kind of data?
You probably want a column of type POINT, a spatial index on such column (which internally is likely to be implemented as an R-Tree), and spatial relation functions on your SQL query to make use of that index.
Start by reading https://dev.mysql.com/doc/refman/8.0/en/spatial-types.html. Take your time, as spatial databases, spatial data types and spatial indices work a bit differently than their non-spatial equivalents.
I am bringing up a tile server with renderd/Mapnik/postgresql. Everything works fine, the problem is that I have no option to restrict my map to a specific region - I need the whole world to be available. On the other hand, I really do not need all the data that the map has (roads, ski slopes, terrain, etc). The planet OSM file is too large, and it takes days to import it to Postgresql.
Is there an option to prepare or to get from somewhere a slimmer OSM map file that will contain only borders and cities?
I created a website (http://www.cartescolaire.paris) that basically loads a GeoJSON and displays it on a map using Leaflet.
This geoJSON is pretty large (over 2 Mb), the loading time can be very long (it doesn't even load on IE 11). More importantly the resulting map is not very responsive when zooming / navigating.
There are around 110 zones (clicking on a point in the map highlights the zone it belongs to), each of them made from dozens of polygons.
However the only important information that I want to visualize is the external boundaries of each zone.
Such a compressed geometry would be much more efficient performance-wise.
The complexity arises from the constraint that the zones shouldn't overlap.
The final result should be disjoint clusters.
Any idea how I could do that ?
Thanks a lot !
Bonjour,
You sound to need merging of polygons, so that you decrease your number of vector features, the weight of your GeoJSON file and map responsiveness. Keeping your resulting polygons disjoint should not be difficult.
You should have plenty resources on SO / GIS Stack Exchange and Google on this, for example:
https://gis.stackexchange.com/questions/118223/merge-geojson-polygons-with-wgs84-coordinate
https://gis.stackexchange.com/questions/118547/convert-geojson-with-multiple-polygons-and-multipolygons-into-single-multipolygo
http://morganherlocker.com/post/Merge-a-Set-of-Polygons-with-turf/
(see also the related posts on SO on the right menu of this page, just above "Hot Network Questions")
Your case might be slightly different as most of your polygons are not adjacent, but are actually separated by empty areas / a margin (streets).
You might also be interested in UTFGrid for the interaction (clicking on the map to open the school associated with that area), as it would dramatically restore your map responsiveness: instead of vector shapes, you have the equivalent of tiles. See an example: http://danzel.github.io/Leaflet.utfgrid/example/map.html
However, I do not think you can visually show the areas with UTFGrid.
But you could combine this approach with canvas-based tiles, or even pre-generate tiles on your server and have them ready for display, rather than keeping a GeoJSON for client-side computation.
Bon courage !