README

geojson-id-disconnected-networks

In a GeoJSON LineString Feature Collection, Identify network areas separate from each other.

When to Use

Many network routing routines accept input from users in the form of Lat/Lng. Generally they use the input Lat/Lng coordinates to locate nearby network nodes from which to start and / or end a route. With an uncleaned network, it's possible that this process may find a node that is not connected to the main network. This library will help identify sub-network areas that are disconnected from the main network.

Example

Here's an example of a network dataset that has several disconnected sub-networks:

Before Processing

Running your GeoJSON network dataset through this tool will yield an additional property subnetworkId on each feature's properties object. The value of subnetworkId is an integer corresponding to the sub-network size rank. (1 is the largest sub-network).

If you map the updated dataset by subnetworkId categorically, you will get a result that looks like:

After Processing

Install

npm install geojson-id-disconnected-networks

Then:


const fs = require('fs').promises;
const idAreas = require('geojson-id-disconnected-networks');


main();

async function main() {

  const geojson_raw = await fs.readFile('./full_network.geojson');
  const geojson = JSON.parse(geojson_raw);

  const altered_network = idAreas(geojson);
  
  // altered_network contains a new geojson property; subnetworkId

  await fs.writeFile('./altered_network.geojson', JSON.stringify(updated_network), 'utf8');

}

How It Works

This library uses Dijkstra's Algorithm to travel the network between an origin and a destination. Because the algorithm travels each possible node along the way, by keeping track of the nodes traveled we can get a full accounting of each sub-network.

Credits

I'm greatly indebted to the work of Stella Chung, who created a very approachable guide to implementing Dijkstra's Algorithm in JavaScript.

You can follow her @stellasometimes on Twitter.

Usage no npm install needed!