89 lines
3.9 KiB
JavaScript
Executable File
89 lines
3.9 KiB
JavaScript
Executable File
import bearing from "@turf/bearing";
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import distance from "@turf/distance";
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import destination from "@turf/destination";
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import lineIntersects from "@turf/line-intersect";
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import { flattenEach } from "@turf/meta";
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import { point, lineString, } from "@turf/helpers";
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import { getCoords } from "@turf/invariant";
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/**
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* Takes a {@link Point} and a {@link LineString} and calculates the closest Point on the (Multi)LineString.
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*
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* @name nearestPointOnLine
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* @param {Geometry|Feature<LineString|MultiLineString>} lines lines to snap to
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* @param {Geometry|Feature<Point>|number[]} pt point to snap from
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* @param {Object} [options={}] Optional parameters
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* @param {string} [options.units='kilometers'] can be degrees, radians, miles, or kilometers
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* @returns {Feature<Point>} closest point on the `line` to `point`. The properties object will contain three values: `index`: closest point was found on nth line part, `dist`: distance between pt and the closest point, `location`: distance along the line between start and the closest point.
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* @example
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* var line = turf.lineString([
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* [-77.031669, 38.878605],
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* [-77.029609, 38.881946],
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* [-77.020339, 38.884084],
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* [-77.025661, 38.885821],
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* [-77.021884, 38.889563],
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* [-77.019824, 38.892368]
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* ]);
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* var pt = turf.point([-77.037076, 38.884017]);
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*
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* var snapped = turf.nearestPointOnLine(line, pt, {units: 'miles'});
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*
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* //addToMap
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* var addToMap = [line, pt, snapped];
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* snapped.properties['marker-color'] = '#00f';
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*/
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function nearestPointOnLine(lines, pt, options) {
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if (options === void 0) { options = {}; }
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var closestPt = point([Infinity, Infinity], {
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dist: Infinity,
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});
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var length = 0.0;
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flattenEach(lines, function (line) {
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var coords = getCoords(line);
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for (var i = 0; i < coords.length - 1; i++) {
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//start
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var start = point(coords[i]);
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start.properties.dist = distance(pt, start, options);
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//stop
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var stop_1 = point(coords[i + 1]);
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stop_1.properties.dist = distance(pt, stop_1, options);
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// sectionLength
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var sectionLength = distance(start, stop_1, options);
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//perpendicular
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var heightDistance = Math.max(start.properties.dist, stop_1.properties.dist);
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var direction = bearing(start, stop_1);
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var perpendicularPt1 = destination(pt, heightDistance, direction + 90, options);
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var perpendicularPt2 = destination(pt, heightDistance, direction - 90, options);
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var intersect = lineIntersects(lineString([
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perpendicularPt1.geometry.coordinates,
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perpendicularPt2.geometry.coordinates,
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]), lineString([start.geometry.coordinates, stop_1.geometry.coordinates]));
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var intersectPt = null;
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if (intersect.features.length > 0) {
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intersectPt = intersect.features[0];
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intersectPt.properties.dist = distance(pt, intersectPt, options);
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intersectPt.properties.location =
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length + distance(start, intersectPt, options);
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}
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if (start.properties.dist < closestPt.properties.dist) {
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closestPt = start;
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closestPt.properties.index = i;
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closestPt.properties.location = length;
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}
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if (stop_1.properties.dist < closestPt.properties.dist) {
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closestPt = stop_1;
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closestPt.properties.index = i + 1;
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closestPt.properties.location = length + sectionLength;
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}
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if (intersectPt &&
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intersectPt.properties.dist < closestPt.properties.dist) {
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closestPt = intersectPt;
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closestPt.properties.index = i;
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}
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// update length
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length += sectionLength;
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}
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});
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return closestPt;
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}
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export default nearestPointOnLine;
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