The Odd Shot

Geotagging

Most images already contain EXIF data such as the date, time, shutter speed, aperture, ISO, etc. Additional information can be added to record the location, including latitude, longitude, and elevation if they are known.

There are two ways of doing this: one is to use a gps device to record the data, and then a program to match the images to the gps track data & automatically insert the data when it has a match. Some cameras do this when they take the image. My cameras don't, so I have recently bought a Garmin eTrex Legend H gps and can download the track data from that . 

The other way is to use a program like Google's Picasa that will display a location on Google Earth, and allow you to select the exact location where you took the image.  For my older images, where I do not have gps data, I am using this technique as I work on each photo. As each image has to be processed manually, this can be very time-consuming, and relies upon the person doing the matching knowing (remembering) EXACTLY where each image was taken, and being able to find it on the map or satellite image displayed by the matching software.

Why do this?  The obvious reason is so that, in years to come, when the photographers memory fades, there is an exact record of the location so it can be revisited. Online albums today often can show image locations on a map, and if the geotag info is present they will do this automatically.

How do you do it? Firstly, you need a gps device that logs your travels. Most in-car navigation units do not do this. Hand-held units designed for bushwalking, etc, usually do. You need to make sure they have sufficient memory to record your usual travel distances in enough detail to be useful. With Garmin units DO NOT use the unit's "save track" function, as saved tracks have the time information deleted! Only the active track has the time information that is needed to match images to the locations. You can use the software for the gps to download the active track & save it to a format your matching program understands (usually gpx format).

Most gps's allow you to set the frequency that they use to record their electronic breadcrumbs. I have found that the Garmin "Auto" setting is adequate for my needs, but some others have suggested that they had better results with a manual setting.

IMPORTANT: Before you set out, make sure your camera is set to the correct time. The gps unit will tell you the exact time, as provided by the gps satellites. Some geotaggers also suggest that the first image you take should be of your gps unit's display, showing the time. That way you can compare the image EXIF time to the gps time displayed to get an exact offset for matching when you get back to the computer.

Obviously, you need to carry the gps with you while photographing. If you leave it in the car, it will only record the location of the car, not your location! Remember also that in buildings, or in dense undergrowth or narrow ravines, etc, the gps might not have an exact location.

When I get back to my computer & download my images from the camera, I also download the gps track to the same folder (others have a different filing method, but I find this sensible).

I am at present still reviewing the numerous programs that match the images to the gps track. My essential requirement is that the program makes no other change to the image or the EXIF data. Many programs seem to add other items, such as "Image created by" to the EXIF. Sorry, but the image was NOT created by that program, so that blacklists it straight away in my estimation.

Since there are several totally free programs that do it quite well, I am not looking at programs that cost money. I am also not looking at programs that require an internet connection to display a map or look up the city, etc. I often download to the laptop in the bush where there is no internet available, so this "feature" is a show-stopper for me.

I intend to post a review when I have finished my assessment of the available software. At present I am using gpsPhoto, which is a rather user-unfriendly  command line program. It is extremely powerful , and seems to work fairly quickly. It is a perl program, and so will work on any computer (Windows, Mac or Linux, for example) as long as a perl environment is also installed.