Function convertLayersToTopojson

topojson/bin/process_geodata.mjs:231–256

({ name, resolution })

}

async function convertLayersToTopojson({ name, resolution }) {
    const regionDir = path.join(outputDirGeojson, `${name}_${resolution}m`);
    if (!fs.existsSync(regionDir)) return;

    const outputFile = `${outputDirTopojson}/${name}_${resolution}m.json`;
    // Scopes with polygons that cross the antimeridian need to be stitched
    if (['antarctica', 'world'].includes(name)) {
        const geojsonObjects = {};
        for (const layer of Object.keys(config.layers)) {
            const filePath = path.join(regionDir, `${layer}.geojson`);
            geojsonObjects[layer] = geoStitch(rewindGeojson(getJsonFile(filePath)));
        }
        // Convert geojson to topojson
        const topojsonTopology = topology(geojsonObjects, 1000000);
        fs.writeFileSync(outputFile, JSON.stringify(topojsonTopology));
    } else {
        // In Mapshaper, layer names default to file names
        const commands = [`${regionDir}/*.geojson combine-files`, `-o format=topojson ${outputFile}`].join(' ');
        await mapshaper.runCommands(commands);
    }

    // Remove extra information from features
    const topojson = getJsonFile(outputFile);
    const prunedTopojson = pruneProperties(topojson);
    fs.writeFileSync(outputFile, JSON.stringify(prunedTopojson));
}

// Get required polygon features from UN GeoJSON
const inputFilePathUNGeojson = `${inputDir}/${unFilename}.geojson`;