determine if a lon,lat point is inside a polygon using great circle calculations
npm install geo-point-in-polygondetermine if a lon,lat point is inside a polygon using great circle calculations
The benefits of great circle calculations are very apparent at high latitudes.
The triangle described here covers the pole even though the latitudes of each point in the triangle
is further south.
`` js`
var geoPointInPolygon = require('geo-point-in-polygon')
console.log(geoPointInPolygon(
[0,90], // north pole
[
[-156.78872,+71.29058], // utqiagvik
[- 51.72157,+64.18347], // nuuk
[+ 88.20270,+69.35350], // norilsk
]
)) // true
also gracefully handles the anti-meridian without special cases:
` js`
var geoPointInPolygon = require('geo-point-in-polygon')
console.log(geoPointInPolygon(
[+178.44149,-18.14161], // suva
[
[+139.69171,+35.68950], // tokyo
[+174.76667,-36.86667], // auckland
[-155.09000,+19.72972], // hilo
]
)) // true
` js`
var geoPointInPolygon = require('geo-point-in-polygon')
var geoPointInPolygonNested = require('geo-point-in-polygon/nested')
var geoPointInPolygonFlat = require('geo-point-in-polygon/flat')
Return whether point is inside polygon.
* polygon is an array of [lon,lat] points or a flat array of [lon0,lat0,lon1,lat1,...]
* is a 2-item array [lon,lat] of decimal degreesstart
* is an inclusive offset into polygon. default 0
* is an exclusive offset into polygon. default polygon.length
* is a [lon,lat] coordinate that is known to be outside the polygon
By default, outside is set to the antipode of the first point in polygon` which should work for
all polygons that span less than 180 degrees of longitude. If your polygon spans >=180 degrees, you
will need to use other domain information to find a point known to be outside the polygon.
npm install geo-point-in-polygon
bsd