Brickblog

In the last couple of weeks I got back to trying something out that I’ve been trying to piece together since 2000/2001. I always thought it might be interesting to track GPS data with images taken from a webcam pointing out the windshield when on a road trip. If you’re wondering why I might think something like this is cool, you should probably read my newly crafted About page to get an idea. This article, is by no means an in-depth how to. There are many sources out there that will guide you step by step with specific hardware software solutions. This article is a broader discussion of my findings and recommendations based on my findings.

Getting GPS Data

Since I take a lot photos when we’re on vacation, I almost always have a laptop with me to back up my shots. Because of this, I’ve settled for the clunkier but much more cost effective Street Atlas 2008 with
Earthmate Lt-120 GPS receiver option for in-car navigation, if needed. The added bonus is that you can do all sorts of cool stuff with it. Including just turn it on and let it track where you are, which is the first step in geotagging. When your done for the day, you can save the GPS log from your day’s journey. Street Atlas saves the log file as a special Delorme .gpl format. There are conversion tools out there that can read that and convert it, sometimes, but Delorme is cool like that, they know you want your data, it’s yours. If you click on the Draw tab, where you would normally design a set of waypoints for a trip, you can import the gpl file as a layer in either track, or waypoint data, to name 2 of the 3 important types. From here you can save it right back out as a .gpx file, or GPS XML file as they are known.

The GPX file is gold, this is what you want for output from what ever you plan to collect your gps data with. It’s an open and specific XML format, which means you can even open the file in something as simple as notepad and view the data. It also means that most of the free software for combining GPS and EXIF data can read it.

A little about EXIF data

Exif data, is metadata stored inherently in some formats of photos. Jp(e)g files and camera raw (raw, nef, etc). You’re probably familiar with it, just not sure what it was called. Most commonly seen on flickr, is the “This photo taken with an ________ camera.” This is just one of the things you can enter in exif data. Other common data that gets stored when you take a photo include iso, f-stop (aperture) and shutter speed to name a few. It doesn’t have to stop there.

A more and more common phenomenon is the inclusion of GPS data in the exif data, which can answer the question “where did you take that photo?” This data typically includes Latitude, Longitude and Altitude. According to the software, you can also automatically include data like Town, State, etc. The best software to do this I found it available for free (donation recommended) For Mac OSX Tiger and Leopard.

Software

The software, GPSPhotoLinker is available at http://oregonstate.edu/~earlyj/gpsphotolinker/. This software is sweet. You can load multiple gpx files and load directories of photos, or individual files. By clicking on the batch tab, you can run a batch write to the photos and be done with it. The sweetest part is that file formats included nef files, Nikon’s raw format. This meant that I didn’t need to convert all my raw files to jpg and then process, as I only keep the nef files on my server and upload the jpgs to flickr then delete them.

Other neat features include the ability to enter in ‘as the crow flies’ locations. Take the photo at left for instance. . . If you click on the image, it will take you directly to the exif info page at flickr about this photo. Scroll down a bit and you’ll see the GPS data. It displays latitude, longitude, altitude, atomic time and that the photo was taken 5km North East of the town center of Rye, New Hampshire. Pretty cool.

This photo was shot with my Nikon D40. I also shot other photos, like the ones on the right, on a timed sequence using a great little web camera from Logitech. The QuickCam Pro for Notebooks is a 2 megapixel (1600×1200) web camera with a Carl Zeiss lens and built in auto focus. I used Webcam Surveyor

to capture photos from the web camera every 3 minutes and save it to the hard drive of my laptop. The effect would be similar to timelapse, but in stead, by saving each photo separate instead of into a movie file, I could pick and choose the photos I wanted to keep, and still create a time lapse movie later if I wanted to. The software is only $30, and can do all sorts of great stuff including time lapse photo/movies, motion detection and recording (with the ability to mask) and other great stuff. It’s worth checking into. You can try it for 30 days to make sure it will work for your needs, I’m sure it will.

Work flow

Make sure your camera’s time matches your local time based on UTC time. HA WHAT? It’s simple. The date/time in the gps stuff will be based on UTC time and adjusted to your area. Look at your gps and see what time it says, and set the clock on your camera to match. The matching of gps location and photo is done with date/time photo was taken and the time stamp in the gps log.

I shoot in raw, probably don’t need to, but I do. I like knowing I have the most flexibility with my photos I can when I get them home. IT gives me warm fuzzies inside. So it was important for me to have software that could work with the raw files. Again, this is why GPSPhotoLinker is so great. However, I did find two things that I had to work around by adjusting my work flow. Really not a big deal now that I know. This is also why I went on several test runs prior to the big trip where I wanted the system to be flawless. I use Adobe Bridge from the Creative Suite to manage my photos. I use it to sort, tag and rate my photos. The first time I tried compiling the results, I did my normal sorting out, adding additional metadata to make it easier to find a photo later, rated the ones I wanted to post to flickr with the stars and did a little color correction, cropping and sharpening, then ran Photlinker to add in the GPS data. Here’s where I hit one small snag. Somehow, the link to the xmp file (xml file containing edits to the nef file) was lost. Metadata stayed, but exposure correction, cropping, and ratings in bridge were lost. I had to go back and do it again.

The other slight snag I hit was that the photos recorded from webcamsurveyor did not have exif data that could be read correctly. I had to use a second piece of software called GPicSync to tag those photos. It was able to read the file created date to enter the gps data into the exif data. I suspect though, that this is more from the way photos from a webcam are saved then GPSPhotolinker.

Summary

I could go into so much detail on this process that you would never read the whole thing, maybe you didn’t. . . Anyone still there? If so, congratulations! There are much better ways to do this, including gps data loggers that clip to your pack if you’re straying from your car, or devices that clip into your hotshoe and write the gps data when the photo is taken. But these can cost from $50 to $400 respectively. I’d be interested in finding out if any of you have tried this out, and what you found worked for you.