Hands on: Location, location, location

On track
I’ve been using a couple of handheld devices to record a GPS track log with which to geotag photos and I’ve had mixed results.

Both devices functioned well and did everything they claimed to in terms of functionality, but while the Garmin Etrex Vista Cx proved well suited to the task of Geotagging, Magellan’s Explorist 500 was more problematic.

In large part, this was due to the fact that the Robo Geo software I’ve been using to acquire the tracklog data and apply it to images is designed to work directly with Garmin units. Having said that, the fact that Magellan’s USB driver wouldn’t install and I had to copy the tracklog from the device memory to an SD card, then use a card reader to import it, didn’t help. This didn’t get me very far as the Explorist tracklogs are stored in a text file that Robo Geo doesn’t recognise.

If you already own a Magellan device you can probably convert the text files to a standard format that Robo Geo can read. A good tool for converting tracklog files between the multitude of available formats, including mapping formats such as Microsoft’s Autoroute, is GPSBabel.

In practice, there’s very little you need to do other than set up the GPS device and – this is crucial – synchronise your camera’s clock with that of the sat-nav unit. The GPS system gets its time from the orbiting satellites, so you can assume it’s accurate. It’s essential that the two clocks are synchronised because Robo Geo gets the date and time information from a photo’s Exif data, then looks up the positional data with the corresponding time in the GPS tracklog. If you forget to synchronise the two devices, Robo Geo and some of the applications mentioned later allow you to specify a time offset.

To ensure synchronicity you must set your GPS receiver to record tracklog data by time rather than distance, and to set a relatively short time interval. If you don’t, it’s possible for the track log to record data at locations before and after you arrived at your location, but not at the actual spot where you took the photo. You’ll need to work out the best interval to ensure that adequate points are recorded without prematurely filling the sat-nav’s memory or, if the device has one, SD card.

Then all you have to do is make sure the unit is switched on and pop it in your camera bag.

Using Robo Geo
On returning from your photoshoot, download your images in the usual way and launch Robo Geo. See the Further info box for details of where to download it and for details of the other geotagging applications mentioned here. The personal licence version of Robo Geo costs $39.95 (about £20). You can download a free trial, but this introduces a deliberate error of up to 1km in the positional data, so it’s of little practical use.

You can select individual images or an entire folder; Robo Geo supports TIFF, PNG, BMP, JPG and DNG. You can’t automatically Geotag PNG and BMP files, because they don’t contain Exif time stamp data, but you can add this information manually to the Robo Geo database. If you’re wondering what use this might be, you could always resave the files as JPEGs or write the geopositional data to the image file as a caption strip along the bottom.

Connecting the Garmin Etrex Vista Cx to the PC and pressing the F3 key automatically downloads the tracklog and populates the Latitude, Longitude and Altitude data fields alongside each image. If your hardware and software combination doesn’t support direct connection you’ll first need to save the tracklog on the GPS receiver, usually in GPX format, before transferring it to the PC and importing it into your tagging application. Though less convenient than a direct connection, this way you at least have a permanent copy of the track log which, unless saved, will be overwritten when the GPS receiver’s memory becomes full.

All that now remains is to decide how you want to attach the location data to the photos. The most obvious choice is to add it to the GPS Exif metadata, so that it’s permanently stored in the image file for you to make use of at any time in the future. You can also have it automatically stamped in caption format along the bottom of each photo.