import * as turf from 'turf' export class GeoOperations { static surfaceAreaInSqMeters(feature: any) { return turf.area(feature); } static centerpoint(feature: any) { const newFeature= turf.center(feature); newFeature.properties = feature.properties; newFeature.id = feature.id; return newFeature; } static centerpointCoordinates(feature: any){ const coordinates = turf.center(feature).geometry.coordinates; coordinates.reverse(); return coordinates; } /** * Returns the distance between the two points in kilometers * @param lonlat0 * @param lonlat1 */ static distanceBetween(lonlat0: [number,number], lonlat1:[number, number]){ return turf.distance(lonlat0, lonlat1) } /** * Calculates the overlap of 'feature' with every other specified feature. * The features with which 'feature' overlaps, are returned together with their overlap area in m² * * If 'feature' is a point, it will return every feature the point is embedded in. Overlap will be undefined */ static calculateOverlap(feature: any, otherFeatures: any[]): { feat: any, overlap: number }[] { const featureBBox = BBox.get(feature); const result : { feat: any, overlap: number }[] = []; if (feature.geometry.type === "Point") { const coor = feature.geometry.coordinates; for (const otherFeature of otherFeatures) { let otherFeatureBBox = BBox.get(otherFeature); if (!featureBBox.overlapsWith(otherFeatureBBox)) { continue; } if (this.inside(coor, otherFeatures)) { result.push({ feat: otherFeatures, overlap: undefined }) } } return result; } if (feature.geometry.type === "Polygon" || feature.geometry.type === "MultiPolygon") { for (const otherFeature of otherFeatures) { const otherFeatureBBox = BBox.get(otherFeature); const overlaps = featureBBox.overlapsWith(otherFeatureBBox) if (!overlaps) { continue; } // Calculate the surface area of the intersection try { const intersection = turf.intersect(feature, otherFeature); if (intersection == null) { continue; } const intersectionSize = turf.area(intersection); // in m² result.push({feat: otherFeature, overlap: intersectionSize}) } catch (exception) { console.log("EXCEPTION CAUGHT WHILE INTERSECTING: ", exception); } } return result; } console.error("Could not correctly calculate the overlap of ", feature, ": unsupported type") return result; } public static inside(pointCoordinate, feature): boolean { // ray-casting algorithm based on // http://www.ecse.rpi.edu/Homepages/wrf/Research/Short_Notes/pnpoly.html if (feature.geometry.type === "Point") { return false; } const x: number = pointCoordinate[0]; const y: number = pointCoordinate[1]; let poly = feature.geometry.coordinates[0]; var inside = false; for (let i = 0, j = poly.length - 1; i < poly.length; j = i++) { const coori = poly[i]; const coorj = poly[j]; const xi = coori[0]; const yi = coori[1]; const xj = coorj[0]; const yj = coorj[1]; const intersect = ((yi > y) != (yj > y)) && (x < (xj - xi) * (y - yi) / (yj - yi) + xi); if (intersect) { inside = !inside; } } return inside; }; } class BBox{ readonly maxLat: number; readonly maxLon: number; readonly minLat: number; readonly minLon: number; constructor(coordinates) { this.maxLat = Number.MIN_VALUE; this.maxLon = Number.MIN_VALUE; this.minLat = Number.MAX_VALUE; this.minLon = Number.MAX_VALUE; for (const coordinate of coordinates) { this.maxLon = Math.max(this.maxLon, coordinate[0]); this.maxLat = Math.max(this.maxLat, coordinate[1]); this.minLon = Math.min(this.minLon, coordinate[0]); this.minLat = Math.min(this.minLat, coordinate[1]); } this.check(); } private check() { if (isNaN(this.maxLon) || isNaN(this.maxLat) || isNaN(this.minLon) || isNaN(this.minLat)) { console.log(this); throw "BBOX has NAN"; } } public overlapsWith(other: BBox) { this.check(); other.check(); if (this.maxLon < other.minLon) { return false; } if (this.maxLat < other.minLat) { return false; } if (this.minLon > other.maxLon) { return false; } return this.minLat <= other.maxLat; } static get(feature) { if (feature.bbox?.overlapsWith === undefined) { if (feature.geometry.type === "MultiPolygon") { let coordinates = []; for (const coorlist of feature.geometry.coordinates) { coordinates = coordinates.concat(coorlist[0]); } feature.bbox = new BBox(coordinates); } else if (feature.geometry.type === "Polygon") { feature.bbox = new BBox(feature.geometry.coordinates[0]); } else if (feature.geometry.type === "LineString") { feature.bbox = new BBox(feature.geometry.coordinates); } else if (feature.geometry.type === "Point") { // Point feature.bbox = new BBox([feature.geometry.coordinates]); } else { throw "Cannot calculate bbox, unknown type " + feature.geometry.type; } } return feature.bbox; } }