Learning Leaflet. Had success with point data. Now want to create polygons.
The process starts with an Access record with a Parcel Identification Number. Using ArcMap desktop, the records are joined to a parcel shape file for the county.
What the best approach to get to Leaflet polygons from here? Like with point data, do I need to add fields to contain the lat/lon data?
I don't need a lot of detail; just a pointer in the right direction. I don't mind doing homework.
My approach would be to convert the shapefile to geojson and then load the geojson into your Leaflet map.
I'm aware of some ArcGIS plugins to export geojson, but an alternative approach is to use the command line tool GDAL (ogr2ogr).
See the links on this answer for more details, but the command will end up being something like the following...
ogr2ogr -f GeoJSON -t_srs "EPSG:4326" [name][.geojson|.json] [name].shp
From there you can preview the results in geojson.io or github before creating your Leaflet map.
Related
I've pulled up a 'plot of land' raster and I'm attempting to georeference it to Openstreetmap. I can get the raster and the OSM to line up however it isn't accurate enough - there are straight lines that have warped.
I'm assuming this is an issue relating to the message, "Used a ballpark transform epsg:27700 to EPSG:3857" that I get when I add OSM as a layer to a new project set to EPSG27700.
As you may easily tell, I'm quite a novice at QGIS!
I need to match gpx file which contains track, that goes straight way, which consists of a few different OSM ways, going one after another with the same angle.
In Graphhopper answer there is a points field, that contains only start and end point of moving.
But I need to get all inner points of OSM ways on that straight way.
if angle in the geometry of one OSM way or angle between previous OSM way and next OSM way changes, graphhopper includes points of angle change in points field
Is there any url option or server config, that can enable
getting all the inner start and end points of OSM ways, disable OSM ways collapsing?
The source code exploation shows, that there is no way to disable OSM ways collapsing without code modification
I'm trying out Mapbox for the first time, and playing around with drawing some polygons in the dataset editor for export to a tileset. However, the polygons in the resulting tileset are not the same as what I create in the editor. The polygons are only very rough, simplified approximations of the originals.
In dataset editor:
In map layer as tileset export:
I understand that Mapbox does vector simplification at certain zoom levels, but these changes are not zoom-dependent. I zoom in all the way and the shapes are still like this.
Moreover, such extreme degredation of the geometries makes tilesets essentially useless for features that require any sort of accuracy, like property lot lines.
Am I missing something, or is this really the expected behavior? Is there really no way to get accurate geometries into a tileset?
UPDATE: It appears this is only happening with shapes I create by drawing in the Mapbox data editor. So far the geometries that I've uploaded as geojson files have gotten converted to tilesets accurately...
I suspect this is because the maxzoom is too low.
When you create a Mapbox Tileset, either by uploading GeoJSON directly as a new Tileset, or by exporting your your Dataset to a Tileset, Mapbox will try to guess an appropriate minzoom and maxzoom of the Tileset.
Sometimes the min/max zoom's used aren't suitable for the map you're trying to create. Since there is no way to specify a maxzoom in either of the two approaches the only alternative is to create your Tileset locally with https://github.com/mapbox/tippecanoe specifying an appropriate maxzoom for your data and then uploading the resulting .mbtiles as a Mapbox Tileset.
I'm working on a project using Leaflet. For this project I've created an interface to draw all the roofs of a large city as polygons. A lot of scripts calculate the surfaces, the addresses, the orientation and so on... I'll store each roof's datas in a geojson file (or files). We expect to get about 10 000 roofs or more. I don't know if Leaflet displays only visibles polygons depending window's boundaries or if all the polygons are drawn, and my problem is to find the better way to do this storage.
In one geojson file. It may be a problem because the 10 000 roofs are computed in the same time and waiting for polygons loading may be very boring for users.
In separated geojson files: for each roof I can approximatively calculate the coordinates of its center and put this roof in the right geojson file depending the lat/lng. By this way I can create (say 20 or 50) differents geojson files and call the right one depending boundaries. Then the question is: to create all the polygons, is it better to call the 6 (or 8 or 10) geojson usefull files for the area on screen, or is it better to create a new dynamic geojson file?
All the roof's datas are stored in a database or in a XML file and I have to detect boundaries and automatically create a dynamic geojson file. But each time user scroll or darg or zoom the map I'm supposed to recreate this unique geojson file...
Do you ever have a similar problem to solve and how do you solve it ? Thx.
I think the second scenario is the most robust, you need tiled GeoJSON tiles. Have a look at Leaflet Plugins. There is one called TileLayer.GeoJSON. Some links on how to create these tiles are on OpenStreetMap wiki.
Could you point me in the right direction on how to create vector tiles from geojson or topojson?
mapnik-vector-tile seems to be the right library but I cannot find a good example.
There seems to be examples of geojson files (14_2620_6331-XXX) but how did the pbf files get created?
Thanks.
Pat.
The vector tile code has a repository with examples, including output in protobuf.