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A Brief Introduction to GPS Photo Linking

by David Goldwasser, contributor to Digital Photography Hacks
06/15/2004

Do you ever look back through your vacation photos and wonder where all of the photos were taken? What if there was a way to have all those images automatically show up as pins on a map or an aerial photograph? It may seem too good to be true, but it can be done. No mirrors or smoke; it's just making use of existing GPS technology.

As you are out recording pictures, your GPS receiver is busy making a digital popcorn trail of your movements. Then when you're back on the computer, a topo map or aerial photograph is pulled from a terraserver on the Internet, and your shots show up on the map as clickable links to your photographs.

In this article I'll provide you with a brief introduction to this fun endeavor to help you get your bearings ... so to speak.

Potential Projects for GPS Photo Linking

I first researched this as a tool for an extensive neighborhood study, but what other uses are there? Well, you could just have fun on a road trip having a passenger shoot photos of roadside attractions. Real estate agents or prospective homeowners could take photos of houses. A scientist studying a particular animal or vegetation could track the locations using this method. Comparing results of previous trips they could study movement or growth of a species. For us nonscientists it could still be a fun way to document hikes or nature walks.


A GPS-driven overview of the photos I took on a walk (created with TopoFusion). If you go to the working example on my web site, you can mouse-over each marker and see a photo of what's at that particular location. Or you can click on the marker for an enlarged image.

GPS Primer

GPS (Global Positioning System) consists of a network of geo-synchronous satellites scattered around the world. The satellites send out a time-stamped signal toward the earth. The GPS receiver, as its name implies, receives a signal from the satellites. It does not, however, communicate back with it. Because the satellites overhead are at different distances from the receiver, it takes longer for some satellite signals to reach the receiver than others. The time gap represents a distance.

So now with a little math the device can triangulate its own location. This is very similar to how the epicenter of an earthquake is determined. To learn more about how GPS works check out the great article on HowStuffWorks.com.

Limitations of GPS Technology

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In general you need a clear view of the sky to successfully use GPS. So indoor use is typically not possible. And depending on the GPS receiver you're using, an urban environment with limited sky view could also be a problem. All GPS receivers are not created equally. Some have much stronger signal receiving strength than others. Generally speaking, more strength is better but that could come at a cost of price and or size. So research this carefully before making a purchase.

Does the Camera Choice Matter?

For the purposes of this endeavor, there are two types of digital cameras. Those that have built-in GPS receivers (or offer accessory attachments), and those that don't.

Cameras with built-in GPS capability are few and far between. Some are costly high-end DSLR cameras, and some are old relics from early days of digital cameras -- such as the 1.4mp Kodak DSC 260 series.

There are a few manufactures that are once again starting to make GPS-enabled cameras, and I hope and expect this activity to increase in the near future. For example, take a look at this cool model from Ricoh.

For the rest of us who don't have cameras with GPS receivers, we can use just about anything we want, as long as it records date and time into the EXIF data. If you shoot in a RAW format you will have to convert the file to JPG.

Types of GPS Receivers

I could write a series of articles on this topic alone, so I'm not going to try to cover everything available. But I do want to go over a few of the basic categories and features of receivers. And most importantly to you, then cover some of the Mac-friendly brands.

At the top end are devices with big, full-color screens and detailed road maps. These will typically let you download additional maps and even provide you with point-to-point directions, telling you where to turn as you drive. This is how a built-in car navigation systems work.

However, this kind of device is no longer limited to the automobile. They are now offered as portable devices that you can take from car to car, or out on the trail. I don't know, since I don't have one of these models, how much of a drain the big color screens are on the battery, as their main use is for in a car or boat with DC outlets. So be sure to check the type of battery that may or may not be included with these high-end devices.

Another class of GPS receivers has no display at all and needs to be connected directly to a computer. Because of the dropping price of the mid-class devices, I suggest bypassing receivers that have to be tethered to a computer.

My favorites, the mid-class devices, have a lot of great options. Most of these are small, all weather or even waterproof, have great battery life, and are very reasonably priced. Most cost from $100 to $400. Most of these models have grayscale displays, although more and more we're seeing color in this range. They have more simplified maps than the car systems and for the most part do not talk you through point-to-point directions.


A Garmin mid-class GPS receiver.

Some of the features to keep in mind while shopping include the ability to upload maps and routes, electronic compass, optional external antenna, and barometric altimeter. I even ran across a combination two-way radio/GPS receiver.

The GPS Photo Workflow

You have lots of ways to hack your system together. Here's one that I've patched together that you can use as a starting point for yours. I do use Virtual PC in my workflow. So if that's not available to you, there's some more hacking you'll have to do.

  • Download GPS track to your Mac using Mac GPSBabel. And here's an interesting resource page for all formats.

    Note: This has to be active track, not saved, or time data may be lost.

  • Download images to computer.
  • Put images and GPS track in shared Virtual PC folder.
  • Launch TopoFusion and follow directions.

    Note: Creation of HTML export will be much quicker if you bring in downsampled images. I sized mine for what I know I wanted them to be on the final web page.

If you are comfortable with HTML code you can modify the code with the HTML editor of your preference. I used Adobe GoLive and integrated it with my iView MediaPro export, which is what I used to downsample the images with in the first place.

Another important note: If you edit the images before using TopoFusion make sure you preserve the EXIF data.

Hardware

Aside from your computer, the two things you'll most likely need are a receiver and a serial-to-USB adapter.

Garmin and Magellan are the two major players for the receivers themselves. Then you might need the Keyspan Serial-to-USB adapter since the GPS receiver will likely come with a serial cable, and you'll probably want to convert it to USB.

A Few More Links

HTML Tools

More Mac Software to Communicate with GPS Devices and TerraServers

More PC-based Software to Link Photos and GPS Data

Mac GPS-enabled Road Atlas Software:

  • Route 66 (mac/pc)
  • DeLorme Street Atlas -- No longer makes Mac version :(

Final Thoughts

As you can see, there's a little hacking involved for Mac-based GPS photo linking. But the results can be quite impressive. If you've been working with these tools, please post a TalkBack below with any tips that you've learned. If there is a Mac software developer out there with some spare time (OK, but I can wish), I would be excited to see a native Mac-based solution for GPS photo linking. My sense is that there would be many thankful Mac photographers.

David Goldwasser is the owner of Inertia, LLC and a contributor to the O'Reilly book, Digital Photography Hacks.


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