nep PRO 10:32pm, 31 August 2007
Boris Mann is organizing a group buy of a cool little GPS device that lets you (easily? kinda) add GPS data to your photos.

Read about it here:

If there are enough buyers, like, more than 5 or more than 10, the price drops. I'm definitely going to get one.

Proggie PRO 9 years ago
interesting concept. Would be neat to have around. I always forget where a photo was taken. That linker program is especially cool! But what advantage (besides size) does this unit have over some of the other gps receivers that have a lot more features and are already supported by the loadmytracks software? At $100 it's not THAT much cheaper than other receivers that have screens, maps, etc. I may be interested in getting a regular GPS unit anyway, so if this thing is only about having a small unit that you can put in your pocket/camera bag, then I may get something else instead.
matt 9 years ago
I've got a relatively wide experience with GPS units, and when it comes to simple passive tracking, rather than navigation, the logging-only units are a lot handier; smaller, longer battery life, and very much fire-and-forget. They tend to have a lot more memory than similarly-priced screened units, which translates to either longer logging times and/or denser logging (both of which can be handy).

For example, I have, on my bike, a Garmin Edge 305, which apart from simple tracking, records speed, cadence (how fast I'm pedalling), altitude, and heart rate. It's got all sorts of readouts (though, oddly, no lat/long), and some rudimentary navigation (reverse or retrace routes). The catch: logging once a second, it only has about 3.5 hours of memory, and uses a 'smart logging' mode to extend that which (by my comparisons) only records things when changes between points pass a particular threshold. The battery lasts about 6 hours, as long as you don't touch any buttons.

On the other hand, a typical logging-only unit would be able to record once a second for 10-12 hours, and battery life would probably extend to around 12 or more hours. The unit Mr Mann is talking about gets about 13 hours of recording at once per second (and is configurable), and 20 hours operation. Track logging is the feature that people probably use the most in practice, and unless you have something specific in mind that they aren't suited for (like geocaching), they're not actually bad units at all.
Proggie PRO 9 years ago
thanks matt! Maybe I'll hold out for this one then. I do need Mac support so hopefully that will come.
filmgoerjuan 9 years ago
Although I'm not interested in getting one, I'm curious to know how (or even if) it allows you to add the GPS data to your photos. Do you have to click something on the device to mark a waypoint representing somewhere you've taken a photo, then somehow link that data to the photos when you download both to your computer? Or is there some amazingly awesome way that all this is done automagically?

It's just that as far as I can see, this device will plot out the route you take using GPS coordinates and there's not really anything specifically that will allow you to (easily) link the data to specific photos. Correct me if this understanding is wrong!
Airchinapilot PRO 9 years ago
Whoah, I think I know who to talk to when it comes to getting a GPS for my road trip...
Proggie PRO 9 years ago
It's not exactly automatic but it's not too difficult either. The way I understand it is you run a program such as GPSPhotoLinker which matches up photos to the points based on the date in the EXIF of your photos. It then saves the GPS coordinate in the photo's EXIF too, which apparently Flickr and Google Maps honour.
matt Posted 9 years ago. Edited by matt (member) 9 years ago
For digital photos Proggie's right, and before that piece of software existed, I wrote my own little script to do the same thing. It's basically a very simple process: your track log is a list of lat/long locations (with times), and you you have a list of photos (with times). Then, you go through each list, and find the times that are closest to each other. Now you know where each photo was taken (with a margin of error of maybe a dozen pixels on the typical zoomed-in map).

Anyway, for those interested in how close to your actual location you can get, here's what I found when I was writing/testing my little bit of code:

If you're logging points faster than every 10 seconds or so, you probably don't even need to interpolate locations that were between points, since you're likely not moving fast enough for that to make a giant difference (GPS accuracy is typically 6-10 metres, which is about as far as you might walk in five seconds, so if a photo is ±5s from a GPS point, it's probably going to be as close to spot-on as you could get). I found you can interpolate location and get a pretty good result with logging points as low as 1 per 5 minutes or so, assuming you don't have too erratic a path.

The big source of error is having a different time on your camera's clock than on the GPS, but even that's not astonishingly difficult to correct for. My solution was to take a photo of my front door when I got home. Because it's at a known location, you can compare the time of the photo and the times on the corresponding GPS points to get the offset between the camera and GPS clocks down to an acceptable level (note: doing it on the way home is better than on the way out, since you have to wait to get a satellite fix when you leave the building, which stretches the time you're hanging around the front door, making the sync less accurate). Or you can just be careful to set your clock on your camera when you're leaving in the morning.
bmann 9 years ago
Cool thread -- thanks for adding all the excellent info, Matt.

As Matt says, this is meant to be the easiest / simplest thing to use, without any dependencies except for batteries. The batteries are rechargeable AND the device can be charged over the built in USB connection. Clip it to your bag, belt loop, wherever ... and log pretty much all the time.

For non USB areas, you can also carry emergency "regular" batteries.

Looks like we're up to 7 people: 3 more and we get a $10USD discount instead of just 5.

And by all means, if folks have experience with other devices...let's talk!
Dang, if I still lived in Vancouver I'd be completely into this. I've always wanted to have a semi-automatic way to link GPS data into EXIF headers.

And the first pocket camera that comes with a GPS built in gets my $$$...
golden_toque 9 years ago
You don't have to be in Vancouver to get in on this deal... Each individual will place the order through Expansys once the numbers are finalized, and after the purchase is made, your total bill will be reduced by the discount. They aren'y all shipping to the same address..

This whole post though is not relevant if you are in Nepal at this momnt, and not somewhere in North America ;-)
bmann 9 years ago
Yes, golden_toque is correct: anyone can order from anywhere -- you will pay and order direct through Expansys, and they will ship to you. They're being quite good about it.
This seems like a great idea, a unit that can do dedicated GPS logging (and lots of it) seems like a great idea to me. I've made the email and have joined the group order... can't wait!

(Not Nepal, just San Francisco...)
Proggie PRO 9 years ago
I'm still interested, but I'm concerned that it will take a while for the mac support to come? Anyone know how soon the mac may be supported, after the developer receives his unit? I guess I could just wait for the support to come and just buy it later at the higher price. Would love to have one on my trip in november though.
matt Posted 9 years ago. Edited by matt (member) 9 years ago
Hard to say. Predicting any sort of software schedule (even if you're the one working on it) is a bit of a black art.

Here, on the one hand, GPS devices work in pretty consistent ways, so it shouldn't be a tough problem, plus the manufacturer has committed to helping a bit, and there's a very good base to build from (GPSBabel and LoadMyTracks both support a lot of different devices already).

On the other hand, if the developer is working (as many do) in his "copious free time," that might stretch things out a bit, and manufacturer support is often longer on promise than reality, since it tends to be managers and PR people volunteering the time of technical sorts, who may not actually have the time to give up.

If I were a betting man, I'd say that if it isn't done in 2-3 weeks, you're probably looking at 2-3 months at the earliest, 6 months at the outside.
Proggie PRO Posted 9 years ago. Edited by Proggie (member) 9 years ago
I just read about this photoGPS device by JOBO in PhotoLife magazine. It attaches to the camera's hotshoe and the software (win/mac compatible) seems very powerful and easy to use. It automates things by adding coordinates as well as city, and even landmarks as tags in EXIF:

More info and photo at canadian distributer's website:

Doesn't look like it's available for sale yet though. Price is more expensive than discussed here, at $160.
Lawrence Junjie Lee 9 years ago
I realize that this thread is now old, but I'm wondering if some of you guys can tell me how much data in terms of hours it can hold if I get the Globalsat receiver to record every 1 second?

Is Matt right to assume that given the accuracy of the receiver, it might be better to set it to record every 5 seconds to increase the number of points it can hold over a longer period of time?

Just to make sure I understand what Matt and others have said, I just need to make sure the GPS logger's data matches the EXIF information in my camera and then I'll just merge the information?

Is tagging the picture's EXIF a lossless process?
matt 9 years ago
- They say 13 hours.

I'm maybe not the right person to say I'm right, but I did do a fair amount of testing. Basically the reasoning is this: if you're walking, you are generally not moving any faster than about 6km/h (and that's a relatively fast pace, as well), which is about 1.6m/s. So every second you're moving much less than the accuracy of the GPS unit, which is about 6-10m. If you're into signal processing or time-series stuff, you can use this extra data to refine your path, but that's generally a bit of overkill for casual use (i.e., does it matter if I'm 2m off of where the doorway is for my local Starbuck's? not really.)

Pragmatically speaking, recording every second loses you absolutely nothing unless you're running out of space on the device. If you are running out of space, though, changing that to every 2 seconds doubles the amount of space for points, and still loses you a negligible amount in terms of accuracy if you're moving at walking pace (i.e., the inaccuracy from the frequency of the sampling is less than the inaccuracy inherent in the device).

Recording every 5 seconds moves the sampling error over the GPS error in theory, but in practice still works impeccably well (at least in my experience) for two reasons: doing a simple interpolation between points minimises the difference, and in the worst case, the extra error introduced amounts to about two pixels on the highest-resolution Google Map (and there's just not much that I can even imagine needs that much accuracy).

I just need to make sure the GPS logger's data matches the EXIF information in my camera and then I'll just merge the information?

That's pretty much it - when a picture's timestamp matches the logger's timestamp, you know where the picture was taken, so you just need to figure out a way to sync the clocks and/or change the timestamps of the pictures afterwards (Lightroom does this pretty handily).

Is tagging the picture's EXIF a lossless process?

Well, if done stupidly (e.g., open and uncompress, then re-compress with new EXIF) it might not be, but I can't think of any reason besides stupidity to do it that way. Every tool and library I've ever used doesn't even touch the JPEG portion of the file.
Lawrence Junjie Lee 9 years ago

So did you set your unit to count every two seconds? I'm guessing that if I set it to every two seconds then I can record roughly 26 hours worth of movements? Yes, I do intend to use this device for my walkathons.

Do you set the GPS logger's time by synchronizing it to your computer's time? If not, how do you set the time on the GPS logger?
matt Posted 9 years ago. Edited by matt (member) 9 years ago
The time on the GPS logger is set by the GPS signals and can't be changed; you have to set your computer/camera to match it. If the device doesn't have a screen (like the globalsat), the best way to do this is to take a picture at a known location, then manually compare the relevant timestamps. This will tell you the offset between the two clocks. The procedure I've used in the past was like this:
1. Go out, do whatever I need to do. Bring the GPS.
2. On the way back to where I started (home, parked car, etc), get ready to do the following fairly quickly:
3. Take a picture (any picture)
4. Immediately turn off the GPS (or stop logging, whichever's easier)

So then you know that timestamp of the last point on your track corresponds to the timestamp of that picture, with a margin of error of a second or two (how long it takes between hitting the shutter button and turning off the logging). Then I'd use exiftool to change the time all the photos by that amount (Lightroom does this too).

The unit I'm using now (which is made for cycling) only has a choice between 3.5hrs @ once per second, or a 'smart' mode that adds points when there's been some undefined yet 'significant' change to the various things it records. If I had a more variable unit, I'd probably pick something between 2-10 seconds, depending on how often I wanted to do the downloading, or how long I expected to be out. With the previous GPS I had, I'd had it set for as long as five minutes between points so that it would last for a week-long backpacking trip (you can change batteries, after all, but not memory), and even that worked out pretty well as far as accuracy goes; the only photos where it really mattered exactly where I was standing, I could move by hand from the computer's guesswork, and usually a pretty short distance.
Lawrence Junjie Lee 9 years ago
Wow, I thought you had to set the time up with the GPS unit before you leave the house. Are you using the Globatsat receiver yourself?
matt Posted 9 years ago. Edited by matt (member) 9 years ago
Nope, though it was tempting for the price, there's too much in the List Of Stuff I Want to justify the $100ish. I've got a Garmin Edge 305, which does some cycling stuff (cadence, lap times, heart rate) as well as GPS. The Globalsat would probably be more useful for general logging, but it doesn't do the cycling bits.

GPS actually works using the slight difference in time signals introduced by transmission delay, so setting the time is generally built right into the unit; the trick is to sync your camera's timestamping to that clock. Relatively simple if the GPS unit displays the time down to the second or so, but when it doesn't, you just need to jump through a couple of hoops.
Lawrence Junjie Lee 9 years ago
Do you use your Garmin Edge 305 for geotagging? Can you use the GPS data from that device on Google Earth?
matt 9 years ago
Yes to both questions.

It's got a USB interface, and you can download the data with a number of different pieces of software. LoadMyTracks (mentioned in Boris Mann's post linked up top) will export to KML (Google Earth) format directly.

For geotagging, I use GPS Photo Linker (that Proggie linked to up top), generally in the batch mode. I used to use a small script that I wrote myself, but the GUI is very nice to have when you need to fine-tune things.
Lawrence Junjie Lee Posted 9 years ago. Edited by Lawrence Junjie Lee (member) 9 years ago
Do you happen to know if an external antenna will help with the tracking if I place the GPS device inside my bag? The DG-100 has a port to add an antenna and I can get a 90 degrees angled antenna for the device for about $20. I'm not sure if it's really worth it or whether it'll aid with the tracking. What do you think? Should I get it?

Also, I would appreciate if someone with this device can comment on how well the DG-100 performs with stopping and relogging to the same file? I think someone mentioned that this can corrupt the data or confuse the device. Is there any truth to this?
matt 9 years ago
I'm not sure if it's really worth it or whether it'll aid with the tracking. What do you think? Should I get it?

Again, it depends what sort of accuracy you think you need. Try it out a few times, and check the accuracy of the fix (this is displayed in various ways by various different software). If it's consistently over ±12m or so, or regularly loses the satellites, I'd say an antenna might help. For what it's worth, my unit (the Edge 305) doesn't have any noticeable drop in accuracy as long as I keep it at the top of my bag.
Lawrence Junjie Lee 9 years ago
I plan on putting the GPS unit at the outer compartment of the bag. Though, it'll be blocked by the nylon of the bag since it's inside the bag and I"ll use a zipper to close it. You think there will be an issue with signal there?
matt 9 years ago
That's pretty much what I do, and my unit does all right, so the DG-100 will probably be OK too. At the very least, it's worth trying a few times before spending any extra money on an antenna.
Lawrence Junjie Lee 9 years ago
So I got the DG-100 and I'm having trouble exporting all of the GPS data. First, I have all of the files for each of the data ticked. Then under "File, Select All Data" is also ticked. I go to export and save it as a KML file. The problem is that Google Earth only detects data for December 29th, 2007. The rest of the data isn't being shown. The only way I can see them is from Globalsat's Data Logger utility. Does anyone here know why? Thanks!
Yeah, the export is a serious pain in the ass. I was working with a guy in Germany to write a tool that does it instead of using the one that comes with the DG-100, but I ran out of time (work is keeping me very busy these days).
I purchased one of these devices and can only echo slightly-less-random, the software it comes with really sucks. I've had problems where it exports all the data but for some reason a few hundred of the data points are identical (and I wasn't standing still either!).

From memory, I think the best success I had was to export the file not as Google Earth but a flat file, then use one of the online utilities available to convert a text file (or csv) to a google earth file. Maybe that will give you more success. For me it easily showed that I had to be very careful with the export. I was then able to check what data points I got before converting it to Google Earth.

Like I say, it's been a while since I looked at it - now it languishes in the draw, maybe waiting for better weather and a trip, but more importantly a lot more patience on my part!
Lawrence Junjie Lee 9 years ago
Argh, I've been busy doing homework so I can't test out alternative software/methods so I'll have to wait until my midterm is over next Tuesday to play with it some more. I really regret buying something like this when I could have spent $200 more and get a Garmin unit that just works. I guess I got what I paid for.
I've just found out that the most recent development tree of gpsbabel contains an import filter for the dg-100. I've tested it out and it works. It's still not packaged up so if you want the feature you have to compile it yourself, but it works and a proper package shouldn't be more than a month or two away.
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