index.js

/**
 * This script takes a directory of images, looks for GPS 
 * coordinates in each file, and then writes the filename and
 * decimal degrees to CSV. If you're pulling images off of your
 * iPhone, using Image Capture is a quick way to move them onto
 * your computer and get started.
 * 
 * Make sure you have imagemagick installed:
 *   $ brew install imagemagick
 * Download these files and install dependencies:
 *   $ npm install
 * Run:
 *   $ node index.js ~/Pictures/iphone/ > images.csv
 * 
 * Graph them on a map using something like TileMill, here's a good starter:
 *   http://mapbox.com/tilemill/docs/crashcourse/point-data/
 */
var im = require('imagemagick');
var fs = require('fs');
var async = require('async');
var path = require('path');

console.log(['file', 'latitude', 'longitude'].join(','));

fs.readdir(process.argv[2], function(err, files) {
  if (err) throw err;
  // Limit im.readMetadata since it doesn't like having too many open file descriptors.
  async.eachLimit(files, 50, readData, function(err) {
    if (err) throw err;
    // done!
  });
});

var readData = function(file, callback) {
  if (file.match(/\.jpg/i) !== null) {
    im.readMetadata(path.join(process.argv[2], file), function(err, metadata) {
      if (err) throw err;
      if (typeof metadata.exif !== 'undefined' && typeof metadata.exif.gpsLatitude !== 'undefined' && typeof metadata.exif.gpsLongitude !== 'undefined') {
        var degreeLatitude = metadata.exif.gpsLatitude.split(', ')
        var degreeLongitude = metadata.exif.gpsLongitude.split(', ')
        var latitude = ConvertDMSToDD(parseInt(degreeLatitude[0].split('/')), parseInt(degreeLatitude[1].split('/'))/100, parseInt(degreeLatitude[2].split('/')), metadata.exif.gpsLatitudeRef);
        var longitude = ConvertDMSToDD(parseInt(degreeLongitude[0].split('/')), parseInt(degreeLongitude[1].split('/'))/100, parseInt(degreeLongitude[2].split('/')), metadata.exif.gpsLongitudeRef);
        console.log([file, latitude, longitude].join(','));
      }
      callback();
    });
  }
  else {
    callback();
  }
};

// http://stackoverflow.com/questions/1140189/converting-latitude-and-longitude-to-decimal-values
var ConvertDMSToDD = function(days, minutes, seconds, direction) {
  var dd = days + minutes/60 + seconds/(60*60);
  // Invert south and west.
  if (direction == 'S' || direction == 'W') {
    dd = dd * -1;
  }
  return dd;
}

package.json

{
  "name": "images",
  "version": "0.0.0",
  "main": "index.js",
  "license": "MIT",
  "dependencies": {
    "imagemagick": "~0.1.3",
    "async": "~0.2.7"
  }
}