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Cuts a file pyramid of static vector tiles from a geojson file.

License: MIT License

Python 53.12% JavaScript 46.88%

labs

labs-geojson2mvt's Introduction

geojson2mvt

Cuts a file pyramid of static vector tiles (.mvt) from a geojson file

Why

We are using mapboxGL in The Capital Planning Platform, and needed an alternative to downloading large static data files for local rendering on the map. We didn't want to put them into a service that would require $ and maintenance, so static vector tiles seemed like a useful alternative for data that will not change very often.

How to Use

Install npm install geojson2mvt

geojson2mvt takes a config object with the GeoJSONs to encode and other options, and builds the pyramid in the specified output directory

var fs = require('fs');
var geojson2mvt = require('geojson2mvt');

var options = {
  layers: {
    layer0: JSON.parse(fs.readFileSync('bus_routes.geojson', "utf8")),
    layer1: JSON.parse(fs.readFileSync('stops.geojson', "utf8"))
  },
  rootDir: 'tiles',
  bbox : [40.426042,-74.599228,40.884448,-73.409958], //[south,west,north,east]
  zoom : {
    min : 8,
    max : 18,
  }
};
// build the static tile pyramid
geojson2mvt(options);

Check out /example for a test project that you can try locally

Options

layers - Object<string,Object> (required) - GeoJSONs to create a vector tileset from. Keys are the layer names that will be used to access data from the respective GeoJSON when displaying data from the MVT.

rootDir - string (required) - the filepath of the directory that will be the root of the file pyramid. It will be created if it doesn't exist.

bbox - array (required) - array of lat/lon bounds like [s,w,n,e]

zoom - object (required) - object with min and max properties for the desired zoom levels in the tile pyramid

Backwards compatibility

Instead of providing a single config object, you can provide two arguments: a geoJson and config object without a layers property, but instead with a layerName property for the name for the imported geoJson in the MVT.

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labs-geojson2mvt's Issues

Multiple layers

Would you be open to accepting a pull request that changes the API slightly to support multiple layers? Something like

var fs = require('fs');
var geojson2mvt = require('geojson2mvt');
 
const busRoutes = './bus_routes.geojson';
const busStops = './bus_stops.geojson';
 
var options = {
  rootDir: 'tiles',
  bbox : [40.426042,-74.599228,40.884448,-73.409958], //[south,west,north,east]
  zoom : {
    min : 8,
    max : 18,
  },
  layers: {
    'layer0': JSON.parse(fs.readFileSync(busRoutes, "utf8")),
    'layer1': JSON.parse(fs.readFileSync(busStops, "utf8"))
  },
};
 
// build the static tile pyramid
geojson2mvt(options);

I could also make this in a backwards compatible way, if desired.

Generating mvt for big geojson files

Reading big files in node

I would like to generate mvt pyramids with your package for really big geojson file(2GB). It is not possible with fs.readFileSync, because of file size. How can I deal with this problem?
Is it possible to generate piramides for many geojson files? Or maybe I should use streams?

Is it use case for multiple layers? Should I cut geojson on many smaller?

command-line interface

Would be great to have available as a shell command, for global install and quick usage from the command line.

See: https://developer.atlassian.com/blog/2015/11/scripting-with-node/#packaging-shell-commands

npm package is out of date

The npm package and this repo do not match

Empty mvt's at zoom levels 15 and up

Maybe an issue with default setting of geojson-vt. Used your example but end up with all mvt's having file size 0 from z=15 and up.

First argument should be a geoJson object, not a path

We should have the first argument be a geojson object, not a path to a geojson file. This will allow people to manipulate their data in javascript before passing it into geojson2mvt()

Not compatible without support for ES6

A bit revision will benefit users of older Node.js versions.

Memory leak?

Running geojson2mvt on a large region tends to crash with the javascript heap size limit being reached. I think something is leaking memory in there. Plot shows heapsize vs tile number. You can see the Garbage collection working but its not grabbing everything.

Not sure if this is an issue in geojson2mvt or one of the required libraries but investigating.