Geo-find-close-polylines NPM

geo-find-close-polylines

Summary

geo-find-close-polylines quickly finds the closest line segments of a polyline on the earth's surface, using a simple spatial index.
This uses GeoJSON and the turf computational geometry library.

Main Functions

I couldn't find these functions in Google Maps libraries, or in turf.
So here they are. Note that lengths are in meters.

mergeBoundingBoxes
Merges two turf bounding boxes. parameters: (a: Geo.IBoundingBox, b: Geo.IBoundingBox)
returns: Geo.IBoundingBox
createSpatialIndexForPath
parameters: (path: GeoJSON.Position[], max_unindexed_length?: number, start_segment_index?: number, end_segment_index?: number)
returns: Geo.SpatialIndexOnPath
findCloseSegmentsNearPoint
parameters: (path: GeoJSON.Feature \<GeoJSON.LineString>, index: Geo.SpatialIndexOnPath, query_pt: GeoJSON.Feature \<GeoJSON.Point> | GeoJSON.Position, distance_m?: number)
returns: Geo.CloseSegment[]

Details

See geo-find-close-polylines.d.ts for the detailed declarations.

Examples

Create a spatial index, and use it to find points on a polyline.

geo = require('geo-find-close-polylines')
var pts = [[0, 0], [1, 0], [2, 0], [3, 1], [4, 1]]
var line = {
    type: 'Feature',
    geometry: {type: 'LineString',coordinates: pts},
    properties: {}
}
// normally, you don't need to specify the max_unindexed_length, but this is a short polyline
// and a short max_unindexed_length demonstrates the decomposition of the spatial index
var index = geo.createSpatialIndexForPath(pts, 2)
var close_segments = geo.findCloseSegmentsNearPoint(line, index, [1.5, 0.001], 120)
// close_segments[0].segment_index == 1
// close_segments[0].distance_to_path == 111.22983322959864
// close_segments[0].pt_on_segment.geometry.coordinates == [1.5000000000000002, 0]

For other examples, see the tests