Lately I’ve become interested in recording the precise locations where I make my photos. I have an iPhone 4S and figured that might make a good GPS receiver, so I set about trying to find the best software, methods and workflow to make the process as accurate and easy as possible.

The best result: iPhone 4S with the GPS Tracks app and Adobe Lightroom.

Following are details of my findings.

Note: as with other aspects of photography, the choice of technology and methods for geotagging is a very personal choice. What follows here is an account of my own journey into the world of geotagging photos while traveling as I do. These methods may or may not work for you, too. If you’re really interested in this stuff, I encourage you to do more of your own research and talk to other people about what they do. To make the best decisions, arm yourself with lots of good information!

Background
In photography, geotagging has been a hot topic for the past couple of years. The term refers to the practice of using GPS coordinates along with mapping software to precisely identify the location where each photo was made.

The potential benefits of geotagging photos include being able to go back to a specific location yourself or to share it with other people. People who do a lot of shooting outdoors — especially in nature — like to pinpoint the place (and time) where a photo was made. Some of my photographer friends have gotten into geotagging very seriously; others (including myself) have been more hesitant.

Location metadata
GPS coordinates can be stored in a photo’s metadata, a portion of a computer file reserved for textual descriptions of various aspects of the image. Using software that can read these coordinates, such as Google Maps, you can plot the places where the pictures were taken, and this information can be useful in a number of ways. When you share the photo, the GPS coordinates can be transferred, too.

I haven’t really embraced geotagging until recently, for several reasons. First, because I use other types of metadata, such as file name and keywords, to identify where my photos were made. Second, because absolute precision hasn’t been that important to me until now. Third, I haven’t seen the benefit in sharing exact locations with other people.

Over the past few months, I’ve become more interested in pinpointing my photo locations, mainly so I can return to them again in the future – especially when I’m leading workshops and tours. So I began a quest to find the perfect solution for my situation.

Technology overview
When you take a picture with your smartphone, GPS coordinates are automatically recorded (most of the time) along with the image data. Some consumer cameras, mostly point-and-shoot models, also have GPS logging capabilities.

But most cameras, especially DSLRs, do not have this capability built in: a raw image file does not typically contain any data about where it was captured.

This means that to tag your photos with GPS coordinates, you need to record the locations separately from the pictures and then combine them later using your computer.

Intro to tracklogs
The best way to record your photo locations is with a tracklog. Using a GPS receiver, you can continually record your position at various time intervals — from a few milliseconds to several minutes — the result of which is a compiled tracklog that contains your complete path from start to finish times. (You can also record waypoints in the GPS device, or use photos from your smartphone for coordinates, but I’ve found that using a tracklog is best when you’re going to pair your locations with photos.)

Lightroom Map Module Plot of GPS Photo Locations

Lightroom Map Module Plot of GPS Photo Locations (click for larger image)

Effectively using a tracklog for geotagging first requires that your camera clock is synched to the GPS time for the location you’re in. (If your camera clock is wrong, you can change the times later.) On the computer, with the tracklog and a set of photos, you can use software to combine each image with the location (based on the time data). When the time of each track point and the time of a photo are the same or nearly identical, the software simply matches them together. The photos can then be plotted on a software map to show the precise location where each photo was taken (see image at right). You can also save those GPS coordinates into the file metadata.

GPS receivers
To record a tracklog you need some type of GPS receiver. You can use any of the myriad handheld devices from Garmin, TomTom, Magellan etc. or you may be able to use your smartphone.

I’ve used an iPhone for a couple of years, through several generations of the device, and at the same time I’ve also had several portable GPS receiver units. I’ve frequently wondered if I could just use my iPhone to record tracklogs, and it turns out the answer is a resounding “Yes”! In fact, the GPS capability of the iPhone 4S (and newer models) is superior to most of the dedicated, handheld GPS receivers on the market today. The trick is finding the right software, or in smartphone parlance, the right “GPS app”.

Smartphone GPS apps
There is a huge range of GPS-enabled software available for modern smartphones. As the hardware chips in the phone have become more sensitive and accurate, so too has the software become more able to take advantage of this capability.

There are several discrete classes of GPS apps; determining each of their strengths is a matter of research and personal trial-and-error. Though you can use GPS for a wide range of purposes, most good GPS apps are made for a specific purpose. For example, when I first bought the iPhone 3GS I also purchased Motion-X, which is a great app for using the iPhone for driving navigation — but not as good for generating tracklogs for photo geotagging.

Ultimately, if your goal is to simply record an accurate track to use in photo processing, use an app dedicated to recording tracklogs.

My research
Over a period of several months, I recorded tracks using the following apps (plus a few others not worth mentioning):

Motion X-GPS
Motion X-Drive
Tracks (free, ad supported)
Tracks (paid version)
CoPilot GPS
GPS Tracks
GeoTag Photos

In most tests, I had several GPS apps running simultaneously, recording tracklogs as I walked on short trips. In other tests, I compared the GPS data captured by the iPhone’s built-in Camera app and SmugMug’s aptly named Camera Awesome to the tracklog from the apps.

I then imported the tracklogs, along with my photos, and combined them in Adobe Lightroom 4. I always reviewed the results just after I finished my walk, so it was fresh in my mind. The results were surprising.

There are several characteristics to consider when evaluating a GPS tracklogging app:

1. Tracklog accuracy. All the apps recorded noticeably different tracks. Even after setting the app to the greatest sensitivity (i.e. most recorded points) some record more points, others less. In cases where the iPhone 4S lost GPS signal, all the apps behaved differently. Some did a good job triangulating and estimating my position and continued to record points, others simply stopped recording points, while yet others recorded points nowhere near where I was. The best apps I used for tracking were Tracks, GPS Tracks and Motion X-GPS, in that order.

2. Ease of exporting. Some apps are much easier than others at getting the tracklogs out of the app and into a file that you can transfer to other software. File names and other textual information is one area where the apps can vary significantly. I like GPS Tracks’ method the best.

3. Cost. To record tracklogs, you don’t need a full-fledged GPS navigation app, and certainly not one with turn-by-turn instructions. The best tracklogging apps for photographers are free of very inexpensive.

GPS Tracks app iconRecommendations
For the iPhone, the best tracklogging app I’ve found is GPS Tracks. Also, the ultra-simply named Tracks is a very close second (and actually best in terms of sheer accuracy), however, it’s a very slimmed down, minimal app that has nowhere near the capability of the GPS Tracks app.

A big surprise: the GeoTag Photos app, which is designed to do precisely the task described, creates remarkably poor tracklogs. Even at the most sensitive setting, the app doesn’t record tracklogs that are accurate when you’re walking around. This major flaw, combined with the awkward methods for exporting and transferring logs, means that it’s basically useless to me.

nat-coalson-gps-tracks-app-1nat-coalson-gps-tracks-app-2

Screen captures from the GPS Tracks app (click for larger images)

Geotagging workflow
After much research, testing and practice, here’s my resulting workflow:

1. Before heading out I always check to that my camera clock is set to the same time as the phone. Since a smartphone usually updates itself when you enter a different timezone, you just need to use that to set the time on your camera.

2. While traveling and walking around taking pictures, I keep the GPS Tracks app on and recording a track. This often means I might leave it on and recording all day, but I pause the recording if I plan to be at one spot for an extended period. (The risk with this is that I might forget to restart the recording when I start moving again.)

My goal is to make one tracklog for each day, but sometimes this isn’t practical and I end up with two or more tracks for the same day.

Tip: recording a tracklog all day can take a lot of battery power. Be sure to shut down all unused apps and system functions. In particular, turning off WiFi as you’re walking around can save huge amounts of battery life. Read about other ways to conserve power on your iPhone.

3. At the end of each day, I export the tracklog by sending it to myself via email. With GPS Tracks and most other apps, you also have other options for exporting such as iPhone folder transfer and Dropbox, etc.

4. Later, when I’m downloading the photos onto my computer, I also copy the tracklogs into the same trip folder.

5. After I import the photos to Lightroom, I use the Maps module to import the tracklog and then Auto-tag the photos.

6. I save out the metadata from Lightroom so the GPS coordinates are stored with each photo.

(For more about the above described Lightroom functions, see my books.)

Conclusions
It’s fun to see exactly where on the map your photos were taken, but having this information also has practical uses. If you want to return to the same spot later, share coordinates with someone else, or just look up the correct name of the place where you shot the photo, having the GPS coordinates is invaluable.

Using an iPhone (or other similar smartphone) and dedicated apps you can effectively record tracklogs that can later be used to plot the exact locations of photos. For iPhone, the GPS Tracks app can’t be beat for accuracy, features and value. I’ll write a comprehensive review of the app when I’ve had more time to use it in the field. Highly recommended!

Thanks for reading. Feel free to leave comments below.

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