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Geocoding Photos: New Fun for Roadskate Reports

timv's picture

I'm not claiming to be any kind of expert here, but the subject of geocoding photographs caught my attention and it seems like something that could be a really natural fit with what folks here are doing. Maybe the links and things I have to share will be helpful to someone, and (perhaps more likely) maybe someone here is actually doing this already and could explain it further to me.

The basic idea is that you can add geographic tags to your digital photos from a skating event or some other trip, and then even embed them in something like a Google map or a Google Earth file. File sharing services such as Picasa and Flickr are also quickly adding support for geographic tags on images.

One of the first links I encountered was to this article on Make magazine's blog. It's a couple of years old and it focuses on adding geographic coordinates to photos by hand (which seems tedious and unlikely to get done a whole lot) but it's still ok for presenting some the basic concepts. A more up-to-date reference would be the Wikipedia entry for Geocoded_photo.

I also got a link to the GiSTEQ PhotoTrackr, a product that could be used to automatically add geotags to pictures from just about any digital camera. It took some research and head-scratching to figure out that this was just a little GPS receiver that always tracks and logs your position, and then reconciles your world coordinates in the GPS log with the photo timestamps ex post facto. As I understand it, the PhotoTrackr never directly connects to the camera at any point in the process. It comes packaged with software that post-processes pictures, inserting latitude and longitude data in the photos' "EXIF headers."

That's why it can work with pretty much any digital camera, probably every one that has a built-in clock, which seem to be just about all of them. Even Sony's geocoding product is advertised as being "compatible with most digital still cameras." (Judging from online reviews, it doesn't have much going for it besides those four magic letters in its brand name.)

At present, geocoding enthusiasts seem to be liking the GlobalSat DG-100 model. And the Mac-using friend who tipped me off to all of this has been getting good results with a Wintec WBT-201. There's also now a "Lite" version of the Gisteq PhotoTrackr.

What makes a geologging device is that (a) it's a fairly small GPS receiver with a high-quality receiving chipset and good or excellent battery life, (b) it has lots of memory onboard to store long GPS tracks, and (c) it has no display or user interface other than perhaps a couple of LED's and a button or two. The last bit is the part that keeps prices low, but as I understand it, anything that can be done with a dedicated GPS photo tracking device can be done just as well with the GPS receiver you already have, as long as it can hold a data log for the entire length of your skate. You just need software to read the data log, which will be in either NMEA or GPX format, and then match timestamps with your photos and edit the photo headers to insert your positions.

I'm a big fan of free, open-source software (particularly because it almost always works with Linux, the free and open-source operating system I use) so I'm very interested in GPicSync, which handles inserting GPS locations into photo metadata. The program's website includes good step-by-step guides to using your geocoded images with services such as Picasa, Flickr, Google Maps, and Google Earth. I particularly like the samples that the author has posted, such as this Google map of his bike ride (through the German Alps?)

(Another open-source application which looks interesting, although not specific to geocoding, is GPSBabel, which aids in transferring waypoints, tracks, and routes from GPS receivers to mapping applications. There's also GPS Visualizer, a free web-based service for turning GPS tracks, street addresses, or geographic coordinates into maps and profiles. GPS Visualizer even includes a web-based version of GPSBabel on the site.)

And this has turned out to be a pretty long blog for something that I don't claim to know much about. But I always enjoy surfing the web, collecting links and learning about totally new stuff, and maybe I'll get some kind of GPS device and try some of this stuff out before next year's skating season gets going. If anyone out there has been working with this kind of stuff, I'd love to hear about your experiences. I think this technology could add a whole lot to our route maps and roadskating reports.


Kremlin, Kolomna Russia Kolomna, Moscow (Province)
55° 6' 23.2632" N, 38° 45' 5.7996" E
Georges Hill Drive
N 52nd St & N Georges Hill Dr
Philadelphia, Pennsylvania 19131
United States
39° 58' 55.6932" N, 75° 13' 27.4224" W
Bear Mountain Bridge to Peekskill MTA Station
Bear Mountain Bridge Rd
Cortlandt Manor, New York 10567
United States
41° 18' 45.2592" N, 73° 57' 58.0356" W
Novosibirsk Novosibirsk, Novosibirsk
55° 3' 12.9456" N, 82° 55' 39.1836" E


roadskater's picture

Geocoding is Definitely Part of the Future

Great stuff, Tim. Ironically enough, I just deleted a bunch of old GPS data conversion and display software last night in a cleanup session for the backup drive. I decided that there'd be new versions and new software when I was ready, and when I had the hardware, hopefully soon.

I wanted to mention two somewhat related pages here, one for user locations:


The other, perhaps more useful, is for node locations:


You can see hints of where I hope we're going on the site with Location information. When posting, there's now a Location section in addition to Places tags. The Location section lets you enter an address and derive the lat lon (when all goes well), or you can use the Google Map to pinpoint a location with the mouse to derive the lat lon (this also when all goes well, and when I was just checking it was not looking right to me). You can geocode your posts now and I set the limit to 10 locations, but could allow more if anyone had the patience, say, to enter the geocoordinates of every rest stop at A2A or some similar info.

Anyway, back to geocoding photos. Some time back, probably two or three years, skatey-mark mentioned this on InlineNC and at the time it was very new. I think he mentioned an app that worked with free black/white sat photos and let you plot your route on the map via GPS and insert photos if you coordinated the time code on the GPS with the camera time.

For those who don't know much about GPS or digital photo file formats, I am not sure we have explained this yet. If your camera knows the time (in our case within a second or two, or more) and you have a GPS (which knows your time and position), you can later go back and see where you were and in the case of many GPS receivers how fast you were going when you took a photo. Just think of all the data your automobile could tell about you if you have a GPS navigation system that stores data.

Most digital cameras store Exchangeable Image Format (EXIF) data along with the photos. For example, on the roadskater photos page (RSN1.net), the newer photos are date- and time-stamped using a program that reads the EXIF data and converts it to a file name using a formula I specified. (Unfortunately, older photos have had much of the EXIF data stripped by the Microsoft Photo Editor program I used and otherwise loved. I have not had time to go back and see if there's a way to correlate archival copies with edited ones, and doubt I will live so long without something else more important or interesting to do.)

So, having the time in your camera automatically attaching this data (plus more cool stuff like shutter speed, aperture and focus info) lets you do some neat things, like derive the finish time for a person crossing the line where you can't see the finish line clock, as long as at least one of your photos shows the clock and the photo time stamp (and your camera battery didn't die, etc.).

Anyway, every true GPS receiver is a clock accurate to a nanosecond or so, as it finds your position by comparing times received from atomic clocks in satellites, triangulating (or more) your position by knowing where the satellites are and how long it took the time signals to reach your device.

Further, the WAAS system and other Differential GPS systems, go one better by taking readings at known locations (like radio towers, especially in the old days) and transmitting the difference between the known and observed locations as a way of correcting for errors in the system (which used to include military scrambling of the signal...in fact, at one point, the USA military was scrambling the signals, and the USA Coast Guard was broadcasting the unscrambling differential corrections! The WAAS satellites are mostly in equatorial orbits as I recall, so you'll often read about needing a good southern exposure for the best results.

Recent spiffy cameras, of course, are starting to include GPS receivers. But for the rest of us, a Garmin or other handheld, or a smaller data logger, can provide the location and time data to go with the camera's time data. Then you just need a program to take the time and position data from the GPS receiver and put that data into the EXIF data in the photo files. I hope that makes sense.

I seem to recall Jay C with a data logger glued to his helmet! Sweet idea.

As for me, I gave up on this a few years ago when I was carrying too much stuff and sometimes batteries would die or the unit would cut off unexpectedly or whatever. The software was clunky and I just grew tired of almost getting it done. Other factors came in to play as well, but that was basically it.

Still, with an inexpensive SONY Cybershot DSC-S50 like I have often used (more on this later I bet) and an inexpensive Garmin eTrex (I used to carry an eTrex Vista), you have what you need. Lots of other combinations would work fine. The trick is to get the data out and to be able to correlate it. That's what the software is for, of course.

Also, this should be possible with output from a Garmin Forerunner 305 (wrist unit) or Garmin Edge 305 (bike mount unit), which combine GPS and HRM. I wonder how many cel phones now have true GPS instead of approximating location from cel tower strength, and how many of these would provide all the data you'd need in a readily accessible format.

It would be great to be able to get this all together with altitude info as well, and that should be possible. Altitude is not as accurate in GPS receivers (the error is usually about 1.5 times the XY error), but can be improved in real time barometrically and later using digital elevation model (DEM) survey map data. Some GPS receivers like the Garmin eTrex Vista correlate barometric variation with the altitude information derived from the GPS signals. The higher you go, the less air is pressing down on the receiver's little head, and it can sense this and remember it!

However, if the weather changes dramatically, specifically if the air pressure changes due to the weather, the barometric data can stray dramatically, making your altitude data dramatically bad. Some GPS units fine tune the barometric data using GPS data to keep the altitude reading in the right general range. This way, you can use barometric data for good accuracy over a short time period, but know the data over longer periods will remain relatively sane even if the weather changes.

I'm hoping to finally bring the GPS and HRM data together in a Forerunner 305 soon, as the digits on my Polar 725i have partially surrendered, and I have had other problems with that HRM, though it served me well for a few years and I still enjoy how the data downloading works and the fact that it doesn't require recharging and such. But it makes sense to have GPS data if possible, and hopefully I'll find the time to edit photos and publish them and correlate it all into photo maps! If not, well it was a nice idea.

When looking the other day at Google Earth views of the skating rink near Moscow, in Kolomna, I enjoyed seeing the photos that had been placed there via geotagging. It made me want to go there to see those beautiful buildings, and to skate in that arena too, of course.

All of this geocoding is coming along, and ever more news sites and social networks will be doing data mashups, until it's no longer cool, of course, and it'll just be normal. Look for automatic tagging to improve and for always more ways of looking at the same stuff in new ways. Geotagging of photos will make it possible to find photos of almost everything it seems! That can be great, or not!

timv's picture


Thanks for the comments and abundant additional info, Blake! I'm looking forward to seeing the ways that geocoding can be integrated with this site.

Regarding altitude information for GPS tracks, I'll bet that it turns out best to just get elevation data based on your lat/long position. Unless you're in an airplane or glider or balloon, you'll be at ground level, right? That's kinda what maps are for. :-)

(I suppose there could be situations like a ramp for a new bridge or a construction detour or something, where you wanted to know whether you had to climb 50 feet or 100 feet elevation, and that Z data might not be available from a map.)

I did what you suggested, using Google Earth to find the Kolomna skating rink. Then for fun, I looked at Novosibirsk and searched for "skate." Know what? There are skating rinks all over that city. And if Google Language Tools and Yahoo Finance didn't lead me astray, I think it costs a US dollar or less to skate. Ya think Artem might be sand-bagging on us?

I was a bit disappointed to see that the "Advanced Search" option for images.google.com doesn't offer geographic searching. (Yet?) That would be neat.

Also, I'm starting to not like the term geotagging so much. When I scan quickly past it, I keep reading it as goattagging, which seems like not a whole lot of fun.

timv's picture

Snap out of it

As far as I can see, the link to Francois Schnell's Google Map of his Alpine bike ride is OK, but the Snap service is choking on that URL and that makes it hard to click through to the page. Here's a long but non-linked link that can be cut-and-pasted if you're having trouble with it. (I think it's a very nice example.):




[Roadskater note: Good catch, timv. I have created two tiny urls:

or to preview the address:

I split the long url timv provided above into multiple pieces so it wouldn't force the text columns wider. The tinyurls should work fine, but the links are there in case they don't work; just be sure to paste all of the url. The Snap preview of the map didn't work on my machine either (XP Firefox), but clicking the link worked. Thanks for your work on this topic!]

eebee's picture

Would've been handy...

That would've been handy afterwards, to have found the hill where I almost killed myself in Philly :-). Took me a long time to locate it on a map.
roadskater's picture

That Curve on Georges Hill Drive Philadelphia Pennsylvania

If you are logged in you can add locations, even to someone else's post (let's hope that'll be good, ha). Anyway, long ago I looked over that spot, because that was a pretty adrenaline soaked moment, indeed. I'll never know how Freddie the girl did a split going down that hill and still saved it. Amazing! Just past this point on the map, I was considering ditching out on the far side of that right bend. It was a flashback to Bear Mountain bridge, or the other side of the mountain on the way back down. Yikes! Thank you Camaro for having that perfect hand-hold rear spoiler.
roadskater's picture

More Work to Be Done

Ok well there's more to be done. The Philly pic works great if you just zoom in and drag the map around. Perhaps I should have attached this to eebee's post about Philly! I put in other locations mostly using geocoordinates, but they didn't stick in the links to the gmaps. IE7 seems to work better than Firefox on this. No time to work on this now! If you add a location that has a full correct address I think it'll work fine on 2nd and subsequent locations, putting in the geocoordinates for you. Not sure. Beta! I'll be moving to new versions of many things before too long, including a different look, ha, but probably just as crowded! We'll see. Skateylove y'all.

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