62 lines
1.9 KiB
JavaScript
62 lines
1.9 KiB
JavaScript
'use strict';
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const proj4 = require('proj4'),
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turf = require('@turf/turf'),
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jsts = require('jsts'),
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utils = require('./utils');
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/**
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* Convert a line buffer to a polygon coordinates
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* @param {*} lineGeoCoors buffer line coordinates
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* @param {*} width in meters
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*/
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function lineBuffer(lineGeoCoors, width) {
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let dBufCoors = [];
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if (!utils.isEmptyArray(lineGeoCoors)) {
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const _width = width || 10; // default is 10 meter
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try {
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// 1. Transform to Earth Azimuthal Equidistant projection centered by the centeroid of the geometry's bounds
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const line = turf.lineString(lineGeoCoors);
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const bbox = turf.bbox(line);
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const bboxPolygon = turf.bboxPolygon(bbox);
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const centroid = turf.centroid(bboxPolygon);
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proj4.defs([
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[
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'EPSG:4326',
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'+title=WGS 84 (long/lat) +proj=longlat +ellps=WGS84 +datum=WGS84 +units=degrees'],
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]);
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const aeqdProjection = `+proj=aeqd +lat_0=${centroid.geometry.coordinates[1]} +lon_0=${centroid.geometry.coordinates[0]} +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs`;
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const projectedCoors = lineGeoCoors.map(co => {
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return proj4(aeqdProjection, co);
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});
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// 2. Do the buffer using JSTS geolib
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const pathCoords = projectedCoors.map(coor => {
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return new jsts.geom.Coordinate(coor[0], coor[1]);
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});
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const geometryFactory = new jsts.geom.GeometryFactory();
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const shell = geometryFactory.createLineString(pathCoords);
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const meters = _width * .5;
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const polygon = shell.buffer(meters, 16, 2); // 16: quadrants point for arc, 2: flat endStyle
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const polygonCoords = polygon.getCoordinates();
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// 3. Transform back to WGS84 latlon
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dBufCoors = polygonCoords.map(co => {
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const proj = proj4(aeqdProjection, proj4('EPSG:4326'), co);
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return [proj.x, proj.y];
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});
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} catch (error) {
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debug(error);
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return [];
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}
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}
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return dBufCoors;
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};
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module.exports = {
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lineBuffer
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};
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