nodejs-globe-elevation

NodeJS module to retrieve elevation from "Global Land One-km Base Elevation Project"

Requirements

You need to download elevation data of the "Global Land One-km Base Elevation Project".

Project's Homepage: http://www.ngdc.noaa.gov/mgg/topo/globe.html

Load GLOBE's data here: https://www.ngdc.noaa.gov/mgg/topo/gltiles.html

Please download and extract GLOBE's files to a directory. This module searches for data files in the folowing paths:

/usr/share/GLOBE-elevation
/usr/share/local/GLOBE-elevation
[current project's directory]/GLOBE-elevation
[current project's directory]/elevation

You may provide any other directory on initializiation.

Installation

Simply install this module with npm

npm install globe-elevation

To install it globally run

npm install -g globe-elevation

Usage

'use strict';
var elevation= require('globe-elevation');
elevation.init({
  dataPath: "path to GLOBE's data files",
  openFileTimout: 1000
});

console.log('Elevation [ 0, 0 ] =? 0:', elevation.getElevation([ 0, 0 ]));
console.log('Elevation at 51.7894(lat), 11.1416(lng) =? 123:', elevation.getElevation({ lat: 51.7894, lng: 11.1416}));
console.log('Elevation at (35.0(lat), -106.6(lng)), (35.1(lat), 106.5(lng)) =? 1624.2:', elevation.getElevation([ { lat: 35.0, lng: -106.6 }, [ () => -106.5, () => 35.1 ] ]));

Initialization

Initialization is optional if your data files are located at one of the above mentioned directories. If not specify it with dataPath.

Furthermore we've optimized file operation for multiple calculations. You may specify with openFileTimeout a timeout in ms, for which any file will be kept open after last access. You may specify 0 to disable this feature (default is 1 second). You should not use much higher values because nodejs waits on process exit for any pending timeout before exiting.

getElevation( location [, onError] )

You may specify a single location or an array of two locations (bounding box).

Any location may be in the format [ lng, lat ] or { lng: lng, lat: lat } or a function returning such values. lat and lng may be functions itselfes returning the corresponding values.

Attention: Please note, that we chose [ lng, lat ] for arrays, because it's MongoDB's internal format for geo locations.

If you specify a bounding box, lng and lat will be iterated over every value inbetween in 1/120 grad steps. The result is the mean value of all elevations.

The optional onError function is called whenever an error occured. It's return value wil be the result of getElevation