Now just where was I ?

I have a few boxes of photos that my mon and day took, and a piece of old luggage with even older photos. Yes, they are probably old family pictures but of course neither date nor location is noted on the back. To add to the lack of information about those photos, not even the names of the subjects are on the pictures. Some of them go back into the early 1900s, or possible before that.

Modern digital photos have solved part of that dilemma, if the photos are properly tagged. If the camera owner has some technical savvy she/or he will have at least set the time and date. Now it is up to them to provide some annotation with the software provided with the camera to add some keywords and tag the photo with appropriate phrases.

Ok, that should take care of the When? and Who? questions, and possibly Where? question, but only in general. And that will be close enough in most casts. But with the advent of low cost GPS devices, also known as Data Loggers the actual spot the photo was taken from can be pinpointed to within a few feet. Is this good or bad? The good thing is that you can return to the same spot for a follow-up photo, say after the seasons change. But it could lead to invasion of privacy if a private residence’s Christmas decorations are located for the world to see.

Some Hi-End cameras even have the GPS function built in. But remember that indoors the GPS signal either does not exist or could be unreliable.

I use a RealTek RGM-3800 Data logger when I feel that the photo should be “Geo Tagged”

There are at least three general classes of consumer GPS receivers; Navigational Devices for use in automobiles and trucks, Hand Held devices for hiking and fishing, and Data Loggers. There are other specialized GPS Receivers too; a couple others come readily to mind, for Aeronautical, and Crop Spraying to name two.

This review is of a Data Logger, specifically the RoyalTek RGM-3800 Data Logger. Data Loggers have one main purpose, to log their position, and log it internally for later retrieval. One of the popular uses of these devices for the general public is to “Geo Tag” photos. This is done by recording the GPS data in a Data Logger, then when Post Processing the photographs matching the GPS data with the Date/Time stamp in EXIF data from the camera, giving a fairly exact report of where the photographer was when the photo was taken. My only experience is with Flickr.Com, when a photo with the proper GPS data in the EXIF header for a photo is uploaded Flickr.Com will be able to display a map with the location data.

I received a RoyalTek RGM-3800 late last year, and have used it ever since and have been happy with it.

This device is small, 1.5″ x 2.75″ x 1″, but the color makes it look like it came from Apple. It is White – visible if you drop it in the undergrowth while out hiking or taking nature photos. It comes with an 18″ lanyard which ends up being about as bulky as the device itself. The one drawback with this lanyard is that the ends snap together, I wouldn’t trust them to hold if the device is swinging from my neck and it gets caught on a sapling, It could come loose and you’d never notice it, but it won’t choke you, that’s a plus for a neck strap like that. The lanyard is long enough to keep in a pocket or your equipment bag. With no display, it can be kept in a pocket all day. There is no need to have it within easy reach but to turn on and off or replace batteries, once every 6 hours or so.

The only User Interface on the device itself is an on/off button, and a small LED, that indicates when the unit is on and satellites have been acquired. The LED is small, not drawing much battery power.

Battery life is fair. It uses 3-AAA batteries, I use rechargeable NiMH. The life of them is about 8 hours. RoyalTek claims “Over 10 hours”, that is probably with fresh Alkaline or NiCAD batteries. 6, 8, or 10 hours is probably more than enough battery life for a day of photography, but marginal for logging a day long hike. Memory is more than sufficient for day long excursions, I’ll talk about that in a paragraph further on.

A CDROM comes with the device but the includee software runs on Windows (maybe Mac too?). I use Linux so I needed to do some searching for suitable software.

The logging interval is settable from 5-sec to 60-sec, I have set mine to 15-sec and use the first log for the desired minute. I’m not moving fast enough to need any better granularity. There are 3 logging modes,

  • 1 – Date/Time, Latitude and Longitude. ( 650,000 data points)
  • 2 – Date/Time, Latitude and Longitude, and Altitude. ( 500,000 data points)
  • 3 – Date/Time, Latitude and Longitude, Altitude and Speed.( 400,000 data points)

For intervals of 15-sec and 12-hour days that about 180-days.

Each logging session is stored as a separate file, with the Linux software these can be downloaded separately, or dumped all at once into one large file. These files are in NMEA format, and can be converted to .GPX files easily using gpsbabel ( available at The RGM-3800-client sourcecode is available under the GPL-v3 license and probably could be compiled for Mac as well. Only standard libraries appear to be needed, I had no problems compiling this on Linux Fedora-9.

What’s my work flow like? Be sure to have a fresh set of batteries, as there is no battery life indicator. I start the logger before I head out for a photowalk. Once I get home I download the entire dataset and convert it into a .GPX file. This all takes just a couple seconds. Then I download the day’s photos from the memory card, with a few hundred images this can take quite a few minutes. Now comes the hardest part of the process. I have some GREP scripts that will search the .GPX file for the first log entry that matches photo’s time, but the log time is UT and the phototime is whatever local time you have set into your camera, this is handled in the script. The script then takes this log entry and formats it for exiftool (another free utility) which then writes the data into the exif header for the photo. One quirk here with Nikon files, exiftool will only modify an original file, if I rename it the exiftool will refuse to modify it. When exiftool does write the new modified file a backup file is saved.

One word of caution, when uploading to, any file that is GeoTagged will be displayed with the map. I don’t GeoTag all files, preferring to tag only those that need to have their location known. A flower bed in front of some private home shouldn’t have it’s location pointed out to the world.

This Data Logger is available from

Yes, I’m happy with mine and would by the same if I needed a second or a replacement.“>


About Mike

I'm an avid bicyclist, that also enjoys Kayaking, Nature Photography, Cross Country Skiing and Geocaching. There's nothing more boring than sitting indoors in "good" weather.
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