A digital camera is a great way to log your boating adventures "” those tiki Bar shenanigans, marina visits, biggest fish or favorite anchorages. But have you ever taken so many photos on a boating trip you forgot which image was taken where? In the past, the hassle and expense of film cameras kept us in check. But with today's digital cameras it's all too easy to rack up hundreds"”or even thousands"”of photos on a single disk.

And that's a fun thing – until you return home to your computer and download a proverbial boatload of image files. Now all those harbors, fishing holes and anchorages become confused. You're not sure if that great new place you discovered is IMG000161.jpg or IMG000279.jpg. If only you had kept field notes, logging each image. But who has the time or inclination to do that while out on the water?

Wouldn't it be convenient to have location information embedded into your image files? That's the logic behind geo-logging or geo-tagging digital photographs, the practice of attaching a location stamp to each image in much the same way as one might add the date and time.

The goal is to supplement a photo's metadata file with precise position information (latitude and longitude).As people do more and more with digital photos, from posting them on blogs, social networks and mapping applications to sharing via mobile phones, the concept of adding location tags makes a lot of sense – and is apt to get more useful as the technology catches on.

The process works using a small camera accessory to record location data and then link it with with each image. Not only can you then recall specifically where each image was shot, but each image can be automatically linked to its location using applications such as mapping software. This lets you marry photos to locations through your laptop navigation software, or through free online services like Yahoo!, Google Maps, Google Earth or bing.com.

Although there are different ways to accomplish this, in all cases the ultimate goal is to embed the location information in the metadata file associated with each image. Even the simplest digital cameras record some metadata "” typically time, date, shutter speed and so on. This information is stored in its EXIF (Exchangeable Image File Format) file. Your aim is to add additional metadata, typically latitude and longitude, to each photo's EXIF file.

Today's photo editing and cataloging software allows you to augment basic metadata with expanded entries such as position, keywords, captions, and ratings.And how you do that, of course, presents some options.

GEO-REFERENCING

As cruising guide authors, we got interested in geo-referencing because our guides have become increasingly packed with photos. In the process of writing our next guide, we have so far shot 1,176 photos. By the end of summer, that will likely top 4,000. We needed a way to manage all this, and several alternatives appeared as we investigated our options.

What we found is that there are three main approaches to geo-referencing digital images, ranging from low-tech to high-tech, manual to automated and (of course) inexpensive to expensive.

In order to geo-reference photos precisely, you must have a GPS device and a digital camera. The GPS collects the location data and the camera collects the visual image. However, there are different ways to marry the location data with the image EXIF file.

FIELD NOTES

The lowest-tech and least-expensive approach is what photographers did for decades before digital photography and geo-referencing: They kept field notes on lenses used, aperture and shutter settings, film speed, and so on. In this case you can use any GPS receiver and manually record the time, latitude and longitude with each photograph taken. While you're at it, you can record other field notes and comments to add to an image's caption and comments fields later.

Our favorite notebook brand is the Bienfang Notesketch line. Although a bit pricey, they are rugged, feature heavy stock that can seemingly be written on with anything, and have lined areas for notes and comments as well as an unlined area which is perfect for sketches and diagrams or taping business cards or brochure tear-offs.

This is the "you're already there" way to geo-reference your images. You can use any digital camera, including point-and-shoot models such as the Canon PowerShot or Nikon COOLPIX series. Any GPS unit will suffice, including an onboard GPS, handheld GPS, chartplotter or even a GPS-enabled smartphone. At home, go to a free mapping site, create a pushpin at a logged location, and upload any photos you'd like to attach. Although not an appropriate choice for cataloging large numbers of photographs, this approach is a simple way to keep track of photos by location and easily share them with friends and family.

By entering a photo's position data, you can see exactly where the picture was taken via online services such as bing.com.

GEO-LOGGING

Geo-loggers are GPS devices that log your position over time. The GPS unit, whether attached to your camera or simply a handheld GPS, records a "bread-crumb" trail at pre-determined intervals creating a track. Images are later geo-referenced by matching each image's time-date stamp (or image sequence) with the logged GPS track. The marrying of GPS and image data occurs via software when you download the images from your camera to your personal computer.

These are small devices, typically weighing only a few ounces, that you simply carry with you as you shoot. We looked at and tested quite a few of these including the AMOD GPS Photo Tracker, Jobo photoGPS, Sony GPS-CS1, and three USGlobalSat models. Prices for these devices, including software, are well under $100. While not all geo-loggers work with all cameras (the software must be compatible with your particular camera make and model), all are compatible with the more common DSLR cameras such as Canon and Nikon. But definitely check before buying.

The USGlobalSat BT-355 is a lightweight Bluetooth geo-logger which marries your "bread-crumb" track to your digital photos via time-date stamps.Because a geo-logger is logging a track of your position, the accuracy of an image's position depends on the granularity of the bread-crumb track. You can set the log interval to achieve the accuracy you need, noting that higher granularity gives a more accurate position but draws more battery power. Most geo-loggers can also output your track in several different data exchange formats, such as .KML and .GPX files. These formats let you easily create a Google Earth layer of your photos (.KML files) or export your geo-referenced photos to your charting and navigation software (.GPX files).

Our favorite in this category was the USGlobalSat BT-335. At $65 we consider this Bluetooth-enabled, SiRF III, 20-channel, NMEA 0183 device with 25-hour re-chargeable lithium-ion battery life and 60,000 waypoint capability to be an ideal choice for any boater wanting to geo-reference their digital pictures.

It also supports all data formats a boater would want, including CSV, TXT, GPX, and KML, and comes with AC and DC chargers. It also works with both Mac and PC.

USGlobalSat also has a versatile sports watch geo-logger with similar functionality that can be used on the boat and then worn for bicycling, hiking, running or other outdoor activities.

GEO-TAGGING

Geo-taggers are GPS sensors that connect directly to the camera and tag each image with instant location data. Just as the camera's shutter can trigger a flash, it can trigger a tiny GPS unit to add position information to that image's metadata. The extraordinary advantage of geo-tagging is that you won't need to later marry the GPS data with the image files via your personal computer.

To satisfy our particular requirements, we chose the Nikon GP-1 which is a recent example of a consumer-oriented, non-professional geo-tagger. The Nikon GP-1 automatically places UTC time, latitude, longitude and altitude into the image's metadata upon exposure, and instantly displays this data on the camera's preview screen. This featherweight one-inch by two-inch device connects directly to the camera's hot shoe, or if you need the flash, via a cable.

A fun and highly versatile way to track position and performance data is the USGlobalSat GH-625M sport watch.

Although the list price is not prohibitive for an amateur (MSRP $269), it only works on higher-end Nikon cameras such as the D90 (MSRP $1300) and above. But like all technology products, look for new models and manufacturers, and for prices to drop sharply in the future.

SEARCHING, SORTING, BLOGGING AND SHARING

As cruising guide authors, we need to know where we captured photos. Images must also be searchable by location and precisely retain all metadata, including location information. But many boaters can also benefit from geo-referencing their images. You can keep track of new anchorages, recall particular harbors, log great fishing spots or document tricky channel approaches. Even better, geo-referenced photos can be shared with family, other boaters, through a blog, as importable files to e-charting software, and through free mapping sites such as Yahoo!, Google Maps, or bing.com.

Photography software, such as Aperture, Lightroom and iPhoto, are rapidly incorporating features to accommodate geo-referenced images. For example, the big excitement with iPhoto 2009 was its "Faces & Places" technology. In addition to facial recognition search, iPhoto now lets you sort through your photos by location and automatically places image map markers. The software understands the GPS data embedded with photos and automatically links to Google Maps.

GPS receivers have become tinier, cheaper, and seemingly ubiquitous. It's only a matter of time before all smartphones, personal computers, and photo editing software incorporate precise location data as a standard component of a photograph's log. In the meantime, boaters have many options to keep track of all their nautical travels and adventures.