geojson-polygon-self-intersections

geojson-polygon-self-intersections

A very simple script to compute all self-intersections in a GeoJSON polygon.

According to the Simple Features standard, polygons may not self-intersect. GeoJSON, however, doesn't care about this. You can use this tool to check for self-intersections, list them or use them in some way.

Usage

Get Node.js, then

npm install geojson-polygon-self-intersections

and use it like so:

var gpsi = require('geojson-polygon-self-intersections');

// poly = ...

var isects = gpsi(poly);

// isects

Where poly is a GeoJSON Polygon, and isects is a GeoJSON MultiPoint.

Alternatively, you can use a filter function to specify the output. You have access to the following data per point:

• [x,y] intersection coordinates: isect
• ring index of the first edge: ring0
• edge index of the first edge: edge0
• [x,y] of the start point of the first edge: start0
• [x,y] of the end point of the first edge: end0
• fractional distance of the intersection on the first edge: frac0
• idem for the second edge: ring1, edge1, start1, end1, frac1
• boolean indicating if the intersection is unique: unique