srtm-elevation/index.js

Read and query HGT files from SRTM, for elevation data with high performance. This module use cached and automatically download HGT files as required.

var SyncTileSet = require('./src').SyncTileSet;

// From Madrid to Paris [ latitude, longitude ]
let locations = [
    [ 40.396764305572056, -3.7408447265625004  ],
    [ 44.465151013519645,  2.2467041015625004  ],
    [ 43.23319741022136 , -2.9278564453125     ],
    [ 43.337164854911094, -1.4337158203125     ],
    [ 44.84418558537004 , -0.6207275390625001  ],
    [ 46.5739667965278  ,  0.36254882812500006 ],
    [ 47.87214396888731 ,  1.9006347656250002  ],
    [ 48.850258199721495,  2.3291015625000004  ]
];

// Calculate min and max lats/lngs
let lats = locations.map(l => l[0]);
let lngs = locations.map(l => l[1]);
let minLat = Math.min.apply(null, lats);
let maxLat = Math.max.apply(null, lats);
let minLng = Math.min.apply(null, lngs);
let maxLng = Math.max.apply(null, lngs);
let timestampBegin = process.hrtime();
let timestampEnd;
var tileset = new SyncTileSet('./data/', [minLat, minLng], [maxLat, maxLng], function(err) {
    if (err) {
        console.log(err);
        process.exit(1);
    }
    timestampEnd = process.hrtime();
    process.stdout.write('\nRetrieve tiles from provider: ' + (timestampEnd[0] - timestampBegin[0]) + 's ' + (Math.abs(timestampEnd[1] - timestampBegin[1]) / 1000000) + 'ms\n');

    timestampBegin = process.hrtime();

    // All tiles are loaded (or downloaded, if they were not already on disk)
    // and queries can be made synchronous.
    locations.forEach(l => {
         console.log(tileset.getElevation([l[0], l[1]]));
    });

    timestampEnd = process.hrtime();
    process.stdout.write('\nElevation calculation time: ' + (timestampEnd[0] - timestampBegin[0]) + 's ' + (Math.abs(timestampEnd[1] - timestampBegin[1]) / 1000000) + 'ms\n');
    process.exit(0);

});