31:[] 2f:{"title":"Calculate Road Intersection Density","cells":[{"id":0,"value":"md`# Calculate Road Intersection Density`","pinned":false,"hidden":false,"mode":"ojs"},{"id":5,"value":"md`\nThis notebook goes over how to calculate the density of roads in an area.\n1) Identify Intersections\n2) Get number of intersections per square grid cell\n3) Convert to GeoTIFF\n`","pinned":false,"hidden":false,"mode":"ojs"},{"id":25,"value":"shpjs = require('shpjs@3.4.3/dist/shp.js')","pinned":true,"hidden":false,"mode":"ojs"},{"id":28,"value":"roads = fetch(\"https://s3.amazonaws.com/geoblaze/osm_roads_clip2.zip\")\n .then(response => response.arrayBuffer())\n .then(shpjs)","pinned":true,"hidden":false,"mode":"ojs"},{"id":159,"value":"viewGeoJSONLink = `http://geojson.io/#data=data:application/json,${encodeURIComponent(JSON.stringify(roads))}`;","pinned":true,"hidden":false,"mode":"ojs"},{"id":168,"value":"html`View Roads in geojson.io`","pinned":false,"hidden":false,"mode":"ojs"},{"id":34,"value":"intersections = {\n const points = [];\n const features = roads.features;\n const numLines = features.length;\n for (let a = 0; a < numLines; a++) {\n const line1 = features[a];\n for (let b = a + 1; b < numLines; b++) {\n const line2 = features[b];\n if (line1 != line2) {\n const intersections = turf.lineIntersect(line1, line2);\n if (intersections.features.length > 0) {\n intersections.features.forEach(intersection => {\n points.push(intersection.geometry.coordinates);\n })\n }\n }\n }\n }\n return points;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":59,"value":"turf = require('@turf/turf@5')","pinned":true,"hidden":false,"mode":"ojs"},{"id":70,"value":"roadsBbox = turf.bbox(roads)","pinned":false,"hidden":false,"mode":"ojs"},{"id":203,"value":"pixelSize = 0.005;","pinned":true,"hidden":false,"mode":"ojs"},{"id":99,"value":"gridCells = {\n const [ minX, minY, maxX, maxY ] = roadsBbox;\n return turf.squareGrid([ minX-pixelSize, minY-pixelSize, maxX+pixelSize, maxY+pixelSize ], pixelSize, { units: 'degrees' });\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":170,"value":"viewGridCellsLink = `http://geojson.io/#data=data:application/json,${encodeURIComponent(JSON.stringify(gridCells))}`;","pinned":true,"hidden":false,"mode":"ojs"},{"id":172,"value":"html`View Grid Cells in geojson.io`","pinned":true,"hidden":false,"mode":"ojs"},{"id":114,"value":"counts = gridCells.features.reduce((counts, gridCell) => {\n intersections.forEach(intersection => {\n const point = turf.point(intersection);\n if(turf.booleanContains(gridCell, point)) {\n const key = JSON.stringify(gridCell);\n if (counts[key]) counts[key]++;\n else counts[key] = 1;\n }\n });\n return counts;\n}, {});","pinned":true,"hidden":false,"mode":"ojs"},{"id":178,"value":"cellsWithIntersections = Object.keys(counts).map(JSON.parse)","pinned":true,"hidden":false,"mode":"ojs"},{"id":182,"value":"bboxCellsWithIntersections = turf.bbox(turf.featureCollection(gridCells.features))","pinned":true,"hidden":false,"mode":"ojs"},{"id":198,"value":"metadata = {\n const [minX, minY, maxX, maxY] = turf.bbox(gridCells);\n const height = Math.round((maxY - minY) / pixelSize); \n const width = Math.round((maxX - minX) / pixelSize);\n return {\n height,\n xmin: minX,\n xmax: maxX,\n width,\n ymin: minY,\n ymax: maxY\n }\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":238,"value":"newValues = {\n\n const results = [new Array(metadata.height).fill(0).map(row => new Array(metadata.width).fill(0))];\n \n cellsWithIntersections.forEach(cell => {\n const [minX, minY, maxX, maxY] = turf.bbox(gridCells); \n const [x, y] = turf.centroid(cell).geometry.coordinates;\n const rowIndex = Math.round((maxY - y) / pixelSize);\n const columnIndex = Math.round((x - minX) / pixelSize);\n results[0][rowIndex][columnIndex] = counts[JSON.stringify(cell)];\n });\n return results;\n};","pinned":true,"hidden":false,"mode":"ojs"},{"id":284,"value":"parseGeoRaster = require(\"georaster@1.5.4\")","pinned":true,"hidden":false,"mode":"ojs"},{"id":286,"value":"newGeoRaster = {\n const [xmin, ymin, xmax, ymax] = turf.bbox(gridCells);\n const metadata = {\n height: newValues[0].length,\n noDataValue: null,\n pixelHeight: pixelSize,\n pixelWidth: pixelSize,\n projection: 4326,\n width: newValues[0][0].length,\n xmin,\n xmax,\n ymin,\n ymax\n }; \n return parseGeoRaster(newValues, metadata)\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":293,"value":"newGeoRaster.toCanvas()","pinned":true,"hidden":false,"mode":"ojs"},{"id":296,"value":"GeoTIFF = require(\"geotiff\")","pinned":true,"hidden":false,"mode":"ojs"},{"id":299,"value":"new_geotiff_as_binary_data = {\n const values = newGeoRaster.values[0].reduce((results, row) => {\n row.forEach(cell => results.push(cell));\n return results;\n }); \n const metadata = {\n height: newGeoRaster.height,\n ModelPixelScale: [pixelSize, pixelSize, 0], \n ModelTiepoint: [0, 0, 0, newGeoRaster.xmin, newGeoRaster.ymax, 0],\n width: newGeoRaster.width\n };\n return GeoTIFF.writeArrayBuffer(values, metadata);\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":302,"value":"dataurl = \"data:image/tiff;base64,\" + btoa(String.fromCharCode(...new Uint8Array(new_geotiff_as_binary_data)))","pinned":true,"hidden":false,"mode":"ojs"},{"id":304,"value":"html``;","pinned":true,"hidden":false,"mode":"ojs"}],"files":"$W31","stdlib":"1","titling":"auto"}