https://github.com/perliedman/node-hgt

Query hgt files (typically SRTM elevation data) with performance
https://github.com/perliedman/node-hgt

Last synced: 4 months ago
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Query hgt files (typically SRTM elevation data) with performance

• Host: GitHub
• URL: https://github.com/perliedman/node-hgt
• Owner: perliedman
• License: isc
• Created: 2015-04-03T11:51:08.000Z (almost 10 years ago)
• Default Branch: master
• Last Pushed: 2020-05-25T04:08:52.000Z (over 4 years ago)
• Last Synced: 2024-09-17T05:10:03.983Z (5 months ago)
• Language: JavaScript
• Size: 966 KB
• Stars: 45
• Watchers: 6
• Forks: 20
• Open Issues: 12
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.md

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README

        
node-hgt

========

[![Greenkeeper badge](https://badges.greenkeeper.io/perliedman/node-hgt.svg)](https://greenkeeper.io/)

[![npm version](https://img.shields.io/npm/v/node-hgt.svg)](https://www.npmjs.com/package/node-hgt) [![Build status](https://travis-ci.org/perliedman/node-hgt.svg?branch=master)](https://travis-ci.org/perliedman/node-hgt)

Read and query HGT files, for example from SRTM, for elevation data with high performance.

Optionally, this module can also use cached and automatically download HGT files as required.

node-hgt tries to be reasonably performant. A rough benchmark shows it can do 1.8M elevation calculations

per second on my years old laptop.

## Install

```

npm install --save node-hgt

```

## Usage

Load and query a HGT file:

```js

    var hgt = new Hgt(__dirname + '/data/N57E011.hgt', [57, 11]);

    

    // Return elevation in meters above sea level.

    // By default, elevation is interpolated bilinearly.

    hgt.getElevation([57, 11])

```

Use a cache directory of HGT files for querying. Missing data will be downloaded

using the elevation data index from [imagico.de](http://www.imagico.de/map/demsearch.php),

by default.

```js

    var tileset = new TileSet('./data/');

    tileset.getElevation([57.7, 11.9], function(err, elevation) {

        if (err) {

            console.log('getElevation failed: ' + err.message);

        } else {

            console.log(elevation);

        }

    });

```

There's also a synchronous tile set, if you know before hand which area you will query:

```js

    var tileset = new SyncTileSet('./data/', [57, 11], [58, 12], function(err) {

        if (err) {

            console.log(err);

            return;

        }

        // All tiles are loaded (or downloaded, if they were not already on disk)

        // and queries can be made synchronous.

        var elevation = tileset.getElevation([57.7, 11.9]);

        console.log(elevation);

    });

```