How do GPS devices for digital cameras work?

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October 1, 2010 at 6:23 pm  •  Posted in Q&A by  •  2 Comments

I noticed that an increasing number of cameras include a built-in GPS device. How do these work and how effective and how complicated are they? Also, is GPS for photography a really useful option?
M.K. Taylor

Yes, several digicams with built-in lenses (Sony DSC-HX5V, Lumix DMC-ZS7 and the Samsung ST1000 and newer WB650) are equipped with a GPS receiver as is one D SLR, the new Sony a55. You can also buy accessory GPS devices such as Nikon’s GP-1 (compatible with some of the newer Nikon D SLRs), a Samsung device for the brand new NX100 and Sony’s GPS-CS3KA  (compatible with any camera that uses SD or Memory Stick Duo cards). Whether built-in or external, either type can record data as to the exact latitude/longitude for each of your photos for later recall with imaging software or with an app such as Picasaweb, Panoramio or Google Map.

While a few cameras are equipped with a built-in GPS receiver, geo-tagging is also possible with other cameras, using one of the external devices such as the Sony CS3KA or the Nikon GP-1. Photos courtesy of Nikon Canada and Sony Canada

These GPS receivers acquire data from three of the satellites orbiting the earth and use triangulation to calculate your exact coordinates at the instant you take each photo. This data is added to the EXIF (or metadata) file that also contains information as to camera settings that were used to make the photo. After downloading the images to a computer, you can view all of the information with imaging software by accessing the Properties or EXIF Data.  You can also view each photo on a map when using one of the applications mentioned above.

Easy to use and free, a Picasaweb album makes it convenient for friends to view your geo-tagged photos with a map of the exact location where each shot was taken. Links also allow for automatically viewing a photo with mapping options at Google Earth or at Panoramio. © 2010 Peter K. Burian

Note: The Sony GPS-CS3KA (like other devices that work with many different cameras) requires an extra step to transfer the information from its internal memory to the image files’ EXIF data folders. This step is not complicated but it’s unnecessary with in-camera GPS or the Samsung and Nikon devices. After shooting for some time, insert the memory card from the camera into the Sony device. Pressing a couple of buttons causes it to apply the geo-tag data to 60 images per batch, taking a couple of minutes.

All of the external devices used for geo-tagging (except the Nikon GP-1 and the new Samsung GPS for the NX100) require you to match each image with the location data that was recorded by the device. This is an extra step but the process is simple and reasonably quick. Photos courtesy of Sony Corporation

A camera with a built-in GPS is the most convenient and adds little to the price but it does consume power so you’ll want to buy a second battery. Of course, this feature is available with only a few cameras. As well, the Sony and Nikon devices that I tested also provided faster signal acquisition than the digicams’ built-in GPS receivers. Especially if you’re a frequent traveler who shoots a lot of  images that you plan to upload to photo sharing sites, geo-tagging will be a real benefit. While location mapping is not essential, it’s definitely nice to have and it’s a cool extra that your friends will appreciate while viewing your on-line albums.

2 Comments

  1. Peter Blahut / October 4, 2010 at 3:49 pm / Reply

    Question: Do you know or would you like to speculate why Nikon does not (yet) include built-in GPS on their higher end DSLR’s? It bothers me that I must buy a separate unit costing $250+ that occupies the hot shoe and 10 pin connection when it could be built in for little cost.

  2. Michael Schmidt / October 5, 2010 at 1:40 am / Reply

    A Minor comment: A GPS receiver typically use as many satellites as are visible to it, up to the limit of the receivers capabilities, typically 12 but this does vary. However a minimum of four, not three satellites are required in order to calculate latitude, longitude and height (there is actually a timing component computed as well, thus the requirement for a minimum of 4 satellites). Another slight adjustment to the article: GPS receivers actually measure distances, not angles to the GPS satellites so do not use tri-angulation. This is a popular misconception but intuitively is easy to visualize, thus often used but alas incorrectly 🙂
    Geo-tagging photos is a great tool, especially when travelling and also when taking pictures from various conveyances, be it aircraft, trains, boats, etc. so long as the GPS receiver is not blocked. GPS satellite signals will be blocked by any physical obstructions including buildings, mountains, cliffs, even dense tree canopy. In these instances one may not get a reliable (or any) position.

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