mirror of
https://github.com/maxogden/geojson-js-utils.git
synced 2025-12-08 18:19:11 +00:00
277 lines
9.6 KiB
JavaScript
Executable File
277 lines
9.6 KiB
JavaScript
Executable File
(function() {
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var gju = this.gju = {};
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// Export the geojson object for **CommonJS**
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if (typeof module !== 'undefined' && module.exports) {
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module.exports = gju;
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}
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// adapted from http://www.kevlindev.com/gui/math/intersection/Intersection.js
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gju.lineStringsIntersect = function(l1, l2) {
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var intersects = [];
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for (var i = 0; i <= l1.coordinates.length - 2; ++i) {
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for (var j = 0; j <= l2.coordinates.length - 2; ++j) {
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var a1 = {x: l1.coordinates[i][1], y: l1.coordinates[i][0]},
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a2 = {x: l1.coordinates[i+1][1], y: l1.coordinates[i+1][0]},
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b1 = {x: l2.coordinates[j][1], y: l2.coordinates[j][0]},
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b2 = {x: l2.coordinates[j+1][1], y: l2.coordinates[j+1][0]},
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ua_t = (b2.x - b1.x) * (a1.y - b1.y) - (b2.y - b1.y) * (a1.x - b1.x),
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ub_t = (a2.x - a1.x) * (a1.y - b1.y) - (a2.y - a1.y) * (a1.x - b1.x),
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u_b = (b2.y - b1.y) * (a2.x - a1.x) - (b2.x - b1.x) * (a2.y - a1.y);
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if ( u_b != 0 ) {
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var ua = ua_t / u_b,
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ub = ub_t / u_b;
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if ( 0 <= ua && ua <= 1 && 0 <= ub && ub <= 1 ) {
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intersects.push({
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'type': 'Point',
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'coordinates': [a1.x + ua * (a2.x - a1.x), a1.y + ua * (a2.y - a1.y)]
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});
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}
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}
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}
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}
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if (intersects.length == 0) intersects = false;
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return intersects;
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}
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// adapted from http://jsfromhell.com/math/is-point-in-poly
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gju.pointInPolygon = function(point, polygon) {
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var x = point.coordinates[1],
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y = point.coordinates[0],
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poly = polygon.coordinates[0]; //TODO: support polygons with holes
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for (var c = false, i = -1, l = poly.length, j = l - 1; ++i < l; j = i) {
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var px = poly[i][1], py = poly[i][0],
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jx = poly[j][1], jy = poly[j][0];
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if (((py <= y && y < jy) || (jy <= y && y < py)) && (x < (jx - px) * (y - py) / (jy - py) + px)) {
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c = [point];
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}
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}
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return c;
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}
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gju.numberToRadius = function(number) {
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return number * Math.PI / 180;
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}
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gju.numberToDegree = function(number) {
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return number * 180 / Math.PI;
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}
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// written with help from @tautologe
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gju.drawCircle = function(radiusInMeters, centerPoint) {
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var center = [centerPoint.coordinates[1], centerPoint.coordinates[0]],
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dist = (radiusInMeters / 1000) / 6371, // convert meters to radiant
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radCenter = [gju.numberToRadius(center[0]), gju.numberToRadius(center[1])],
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steps = 15, // 15 sided circle
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poly = [[center[0], center[1]]];
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for (var i = 0; i < steps + 1; i++) {
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var brng = 2 * Math.PI * i / steps;
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var lat = Math.asin(Math.sin(radCenter[0]) * Math.cos(dist) +
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Math.cos(radCenter[0]) * Math.sin(dist) * Math.cos(brng));
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var lng = radCenter[1] + Math.atan2(Math.sin(brng) * Math.sin(dist) *
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Math.cos(radCenter[0]),
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Math.cos(dist) - Math.sin(radCenter[0]) *
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Math.sin(lat));
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poly[i] = [];
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poly[i][1] = gju.numberToDegree(lat);
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poly[i][0] = gju.numberToDegree(lng);
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}
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return { "type": "Polygon", "coordinates": [poly] };
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}
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gju.rectangleCentroid = function(rectangle) {
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var bbox = rectangle.coordinates[0];
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var xmin = bbox[0][0], ymin = bbox[0][1], xmax = bbox[1][0], ymax = bbox[1][1];
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var xwidth = xmax - xmin;
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var ywidth = ymax - ymin;
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return { 'type': 'Point', 'coordinates': [xmin + xwidth/2, ymin + ywidth/2] };
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}
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// from http://www.movable-type.co.uk/scripts/latlong.html
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gju.pointDistance = function(pt1, pt2) {
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var lon1 = pt1.coordinates[0], lat1 = pt1.coordinates[1],
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lon2 = pt2.coordinates[0], lat2 = pt2.coordinates[1],
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dLat = gju.numberToRadius(lat2 - lat1),
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dLon = gju.numberToRadius(lon2 - lon1),
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a = Math.sin(dLat/2) * Math.sin(dLat/2) +
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Math.cos(gju.numberToRadius(lat1)) * Math.cos(gju.numberToRadius(lat2)) *
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Math.sin(dLon/2) * Math.sin(dLon/2),
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c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
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return (6371 * c) * 1000; // returns meters
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},
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// checks if geometry lies entirely within a circle
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// works with Point, LineString, Polygon
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gju.geometryWithinRadius = function(geometry, center, radius) {
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if (geometry.type == 'Point') {
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return gju.pointDistance(geometry, center) <= radius;
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} else if (geometry.type == 'LineString' || geometry.type == 'Polygon') {
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var point = {};
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var coordinates;
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if (geometry.type == 'Polygon') {
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// it's enough to check the exterior ring of the Polygon
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coordinates = geometry.coordinates[0];
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} else {
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coordinates = geometry.coordinates;
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}
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for (var i in coordinates) {
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point.coordinates = coordinates[i];
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if (gju.pointDistance(point, center) > radius) {
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return false;
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}
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}
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}
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return true;
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}
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// adapted from http://paulbourke.net/geometry/polyarea/javascript.txt
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gju.area = function(polygon) {
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var area = 0;
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// TODO: polygon holes at coordinates[1]
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var points = polygon.coordinates[0];
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var j = points.length - 1;
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var p1, p2;
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for (var i=0; i < points.length; j = i++) {
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var p1 = {x: points[i][1], y: points[i][0]};
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var p2 = {x: points[j][1], y: points[j][0]};
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area += p1.x * p2.y;
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area -= p1.y * p2.x;
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}
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area /= 2;
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return area;
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},
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// adapted from http://paulbourke.net/geometry/polyarea/javascript.txt
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gju.centroid = function(polygon) {
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var f, x = 0, y = 0;
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// TODO: polygon holes at coordinates[1]
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var points = polygon.coordinates[0];
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var j = points.length - 1;
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var p1, p2;
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for (var i=0; i < points.length; j = i++) {
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var p1 = {x: points[i][1], y: points[i][0]};
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var p2 = {x: points[j][1], y: points[j][0]};
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f = p1.x * p2.y - p2.x * p1.y;
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x += (p1.x + p2.x) * f;
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y += (p1.y + p2.y) * f;
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}
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f = gju.area(polygon) * 6;
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return { 'type': 'Point', 'coordinates': [y/f, x/f] };
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},
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gju.simplify = function (source, kink) {
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/* source[] array of geojson points */
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/* kink in metres, kinks above this depth kept */
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/* kink depth is the height of the triangle abc where a-b and b-c are two consecutive line segments */
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kink = kink || 20;
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source = source.map(function(o) { return {lng: o.coordinates[0], lat: o.coordinates[1]} });
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var n_source, n_stack, n_dest, start, end, i, sig;
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var dev_sqr, max_dev_sqr, band_sqr;
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var x12, y12, d12, x13, y13, d13, x23, y23, d23;
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var F = ((Math.PI / 180.0) * 0.5 );
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var index = new Array(); /* aray of indexes of source points to include in the reduced line */
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var sig_start = new Array(); /* indices of start & end of working section */
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var sig_end = new Array();
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/* check for simple cases */
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if ( source.length < 3 ) return(source); /* one or two points */
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/* more complex case. initialize stack */
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n_source = source.length;
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band_sqr = kink * 360.0 / (2.0 * Math.PI * 6378137.0); /* Now in degrees */
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band_sqr *= band_sqr;
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n_dest = 0;
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sig_start[0] = 0;
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sig_end[0] = n_source-1;
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n_stack = 1;
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/* while the stack is not empty ... */
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while ( n_stack > 0 ){
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/* ... pop the top-most entries off the stacks */
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start = sig_start[n_stack-1];
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end = sig_end[n_stack-1];
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n_stack--;
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if ( (end - start) > 1 ){ /* any intermediate points ? */
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/* ... yes, so find most deviant intermediate point to
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either side of line joining start & end points */
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x12 = (source[end].lng() - source[start].lng());
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y12 = (source[end].lat() - source[start].lat());
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if (Math.abs(x12) > 180.0)
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x12 = 360.0 - Math.abs(x12);
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x12 *= Math.cos(F * (source[end].lat() + source[start].lat()));/* use avg lat to reduce lng */
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d12 = (x12*x12) + (y12*y12);
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for ( i = start + 1, sig = start, max_dev_sqr = -1.0; i < end; i++ ){
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x13 = (source[i].lng() - source[start].lng());
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y13 = (source[i].lat() - source[start].lat());
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if (Math.abs(x13) > 180.0)
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x13 = 360.0 - Math.abs(x13);
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x13 *= Math.cos (F * (source[i].lat() + source[start].lat()));
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d13 = (x13*x13) + (y13*y13);
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x23 = (source[i].lng() - source[end].lng());
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y23 = (source[i].lat() - source[end].lat());
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if (Math.abs(x23) > 180.0)
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x23 = 360.0 - Math.abs(x23);
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x23 *= Math.cos(F * (source[i].lat() + source[end].lat()));
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d23 = (x23*x23) + (y23*y23);
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if ( d13 >= ( d12 + d23 ) )
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dev_sqr = d23;
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else if ( d23 >= ( d12 + d13 ) )
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dev_sqr = d13;
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else
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dev_sqr = (x13 * y12 - y13 * x12) * (x13 * y12 - y13 * x12) / d12;// solve triangle
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if ( dev_sqr > max_dev_sqr ){
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sig = i;
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max_dev_sqr = dev_sqr;
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}
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}
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if ( max_dev_sqr < band_sqr ){ /* is there a sig. intermediate point ? */
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/* ... no, so transfer current start point */
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index[n_dest] = start;
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n_dest++;
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}
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else{
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/* ... yes, so push two sub-sections on stack for further processing */
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n_stack++;
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sig_start[n_stack-1] = sig;
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sig_end[n_stack-1] = end;
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n_stack++;
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sig_start[n_stack-1] = start;
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sig_end[n_stack-1] = sig;
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}
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}
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else{
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/* ... no intermediate points, so transfer current start point */
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index[n_dest] = start;
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n_dest++;
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}
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}
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/* transfer last point */
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index[n_dest] = n_source-1;
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n_dest++;
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/* make return array */
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var r = new Array();
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for(var i=0; i < n_dest; i++)
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r.push(source[index[i]]);
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return r.map(function(o) { return {type: "Point", coordinates: [o.lng, o.lat]} });;
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}
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})(); |