Use polygon-clipping for dissolve

BlinkTagInc · Nov 20, 2020 · ed538ac · ed538ac
1 parent 20cf16c
commit ed538ac
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Showing 4 changed files with 83 additions and 342 deletions.
diff --git a/lib/formats/lines-dissolved.js b/lib/formats/lines-dissolved.js
@@ -1,8 +1,10 @@
 const gtfs = require('gtfs');
 const buffer = require('@turf/buffer');
-const dissolve = require('@turf/dissolve').default;
+const { geomEach } = require('@turf/meta');
+const { multiPolygon } = require('@turf/helpers');
+const polygonClipping = require('polygon-clipping');
 
-const { simplifyGeoJSON, stripNonAgencyProperties } = require('../geojson-utils');
+const { simplifyGeoJSON } = require('../geojson-utils');
 
 module.exports = async (config, routeId, directionId) => {
   const query = {};
@@ -15,8 +17,21 @@ module.exports = async (config, routeId, directionId) => {
   const lines = await gtfs.getShapesAsGeoJSON(query);
   const bufferedLines = buffer(lines, config.bufferSizeMeters, { units: 'meters' });
 
-  // Need to simplify geojson before dissolving otherwise turf.dissolve can hang.
-  const dissolved = dissolve(simplifyGeoJSON(bufferedLines, config));
+  const geometries = [];
+  geomEach(bufferedLines, (geometry) => {
+    if (geometry.type === 'MultiPolygon') {
+      geometries.push(geometry.coordinates);
+    }
+    if (geometry.type === 'Polygon') {
+      geometries.push([geometry.coordinates]);
+    }
+  });
 
-  return stripNonAgencyProperties(dissolved);
+  const unioned = polygonClipping.union(...geometries);
+  const geojson = multiPolygon(unioned);
+
+  // Assign agency_name
+  geojson.properties.agency_name = bufferedLines.features[0].properties.agency_name;
+
+  return simplifyGeoJSON(geojson, config);
 };
diff --git a/lib/formats/stops-dissolved.js b/lib/formats/stops-dissolved.js
@@ -1,8 +1,10 @@
 const gtfs = require('gtfs');
 const buffer = require('@turf/buffer');
-const dissolve = require('@turf/dissolve').default;
+const { geomEach } = require('@turf/meta');
+const { multiPolygon } = require('@turf/helpers');
+const polygonClipping = require('polygon-clipping');
 
-const { simplifyGeoJSON, stripNonAgencyProperties } = require('../geojson-utils');
+const { simplifyGeoJSON } = require('../geojson-utils');
 
 module.exports = async (config, routeId, directionId) => {
   const query = {};
@@ -16,10 +18,21 @@ module.exports = async (config, routeId, directionId) => {
 
   const bufferedStops = buffer(stops, config.bufferSizeMeters, { units: 'meters' });
 
-  // Run dissolve twice to handle dissolves missed on the first pass.
-  // Need to simplify geojson before dissolving otherwise turf.dissolve can hang.
-  const dissolved = dissolve(simplifyGeoJSON(bufferedStops, config));
-  const dissolved2 = dissolve(dissolved);
+  const geometries = [];
+  geomEach(bufferedStops, (geometry) => {
+    if (geometry.type === 'MultiPolygon') {
+      geometries.push(geometry.coordinates);
+    }
+    if (geometry.type === 'Polygon') {
+      geometries.push([geometry.coordinates]);
+    }
+  });
 
-  return stripNonAgencyProperties(dissolved2);
+  const unioned = polygonClipping.union(...geometries);
+  const geojson = multiPolygon(unioned);
+
+  // Assign agency_name
+  geojson.properties.agency_name = bufferedStops.features[0].properties.agency_name;
+
+  return simplifyGeoJSON(geojson, config);
 };