After thinking about it for a longer time I finally decided to try GPS together with the D300. A cable based solution was out of the question. Not only would it be bulky to use but the choice of GPS devices with serial connectivity is very limited too. By far the most GPS receivers use bluetooth and the others USB connections. Today I am aware of two bluetooth solutions for the Nikon. One is the blue2can, a device built by a professional company with support and the like, the other is this: Foolography Unleashed built by a one-person company, the one I settled for.
Let me first introduce how all of that works before going into the details.
The Unleashed module comes with a special usb-to-serial cable which is used to program it. As usual the first thing is to install the device driver - done in a minute - then you plugin the cable to the computer, the installed drivers will be recongnized and you end up with an additional com port. Now you plug in the Unleashed module to the other end of the cable and start the Unleashed configuration program to search for all available Bluetooth devices and pair it with the GPS device. Once this step is done, you unplug the module and insert it to the 10 pin port of the camera. Turn on the camera, and two seconds later the GPS symbol is shown telling that a GPS device was found and is sending correct positional data.
This ease of use is really something that I was amazed a lot. I expected that ... I don't know, you have to turn on the GPS receiver first and then the camera or nonsense like that. Or that it takes a minute until the camera is ready. Nothing like that!
The next step was to go to the GPS menu of the camera and tell it to enable the "auto meter off". When you click on AF-S or press the shutter halfway, the 10 pin port gets power, and....if you don't give the GPS unit its five seconds to connect, you will get a picture but without the GPS coordinates. To prevent that, this menu item keeps the exposure meter "On" all the time the camera is turned on and(!) a GPS unit is connected. The second menu item is to view the live GPS coordinates the camera receives. So I was able to see I am 50° North, 0° 23' E and 60m high. Excuse me? 0° 23' East? Very unlikely. By connecting the GPS mouse to the computer and running an excellent tool called GPSDiag (e.g. found here) I could validate that the GPS receiver is working fine and tells we are 007°. Just to make sure, the degrees are wrong, not the minutes & seconds! It was when I started to add pictures to google maps and wanted to correct them manually that I figured, the problem was with viewing the GPS coordinates. The values inside the EXIF GPS fields have been correct anyway! Oh dear. I could even see from which position of the tennis court the picture was taken! I would give it an accurancy of about 2 meters? Reporting this problem to Foolography we had been able to confirm that this bug in the D300 View GPS Coordinates screen is common to all GPS receivers, it was just overlooked by now. So don't get scared if the coords are off, it is just the viewing. The one place where it really matters are the EXIF fields and there all is in order. Nevertheless I have reported the bug to Nikon.
What is particularily neat about the Skytraq100+ GPS receiver is its power management. If you turn off the camera (the bluetooth connection), it will go into a standby mode five minutes later. Turn on the camera again and it will take 5 seconds until the camera is connected to the GPS receiver, and then another n-seconds until it receives a valid GPS position - the TimeToFirstFix (short TTFF) which is between 1 second and 10 seconds from what I have seen. Depends on your GPS receiver obviously but all modern ones should be similar.
Why spend that much money? Doesn't a GPS Logger do the same job?
GPS Loogers are devices that contiously record the current position in memory and later you can read that file(s) and given the timestamp of the GPS signal and the time value the camera stored in the EXIF and some software you can merge the two pieces into a geotagged jpeg. Those GPS loggers are cheap, they record the position either every n seconds or whenever moved a certain distance. They have enough memory to store a lot of records and the software that merges the information is supposed to be easy to use too. It is the handling and the numerous things that could go wrong. You plugin the logger and download the location files via some software. Then you disconnect, connect the camera, download its images. Then you start the software to merge the two. You won't see if the GPS logger stopped working for whatever reason, whereas at the camera display you will look whenever you turn it on. The camera time might be off a few seconds or even a minute (or an hour because of daylight saving time?) and you will have no chance to correct that, whereas the bluetooth solution has all at once, it even shows the camera time plus the GPS time with atomic clock precision in the EXIF data.
When I put all that together, how many hours of manual work it will take to sync that data over the months and years, and assign labor "costs" to that, I'd say the bluetooth solution is cheaper. Might not be worth it but cheaper.
What are the differences between the two bluetooth products?
Bluetooth supports multiple pairing methods, methods to make sure that e.g. your headphone doesn't suddenly receive somebody else's calls. The Blue2Can device pairs with the next available bluetooth device supporting the SPP (serial line protocol) which very likely will be a GPS unit. Of course you could say that "stealing" the coordinates information from somebody else's GPS unit who is 10m away is no big deal. But now imagine that GPS device you are connected is moving out of range. You end up with no GPS data until you turn off the camera and turn it on again. Not too nice, is it? Another issue could be, you connect to the GPS receiver but it is used by some other computer, e.g. your handheld is using one GPS mouse, the camera is supposed to use the other. You cannot control which device the camera connects to and if it is the used one, the bluetooth error "cannot open serial port" is returned as it is used by the other device already. And that's it - no GPS data. No reconnect. Just no data and no clue why.
With the Unleashed module the GPS device is really bound to it. Yes, you can choose the other connection mode also but why would you? And this was really the key reason for myself - less troubles. Just turn on the camera and you are ready.
The concern I had however was, can you trust a one man shop? What if the programming cable has no driver for Longhorn or whatever operating system I will use in five years? Or the configuration software? Actually, the Unleashed module is using components from well established companies, just tied those together and made it work. So both software components will likely have full support, more support than a small company somewhere. The downside of this approach are higher costs. That bluetooth to serial converter used is likely this one http://www.sena.com/products/industrial_bluetooth/esd.php and it costs 50EUR already. Add the programming cable, the housing etc and just the material costs get to 150EUR or more I guess. So the price is okay, I'd say. And both products cost about the same anyway.
One concern raised often is the battery drain caused by the bluetooth plug. I do not want to argue that it does not consume much according to the specs, I rather say: First, if you turn off the camera the module gets disconnected from power and hence does not change anything from before. And second, the battery of the camera still lasts for four to five days usage. Actually, I can't see any difference compared to before.
The other thing I have read was the question how tight the plug sits. The camera would have a screw thread, but the Unleashed module does not. It just plugs in. And frankly, I would have no idea how to use the screw thread given the small dimensions of the device. It sits tight, it cannot fall off by itself, it is well protected by the camera body so no way it can dangle itself and get ripped off. And still you can unplug it with some force but without the fear of breaking something. So in that respect it is really well balanced.
And before I forget, the flash popup button is fully accessible, its control button below good enough. Given I never changed the flash setting via this lower button I wouldn't even care.
It seems to be sort of a personal thing, maybe my German attitude, but everything should be made perfect. No matter what it costs, no matter if there is not even reasoning behind. It is just a philosophy. Same thing with the Unleashed module - I would love to see it getting perfect. The one thing I can certainly not live with is, the camera is no longer resistant to spray water. Geotagging just sounds like synonym to exposing the camera to not-so-good weather. The plug body itself is sealed, however it has the mini-USB and the remote shutter connectors open, what makes it worse they are on the upper side. Fixing that is simple, in worst case an adhesive tape will do the trick. Or I find some plastic pieces from other devices to seal them. But the 10-pin connector to the camera is exposed. I will put some gasket around, the module will create enough pressure on to seal it without sliding slowly out over the time I am sure.
And then there are more features one can think of. I considered if having the compass heading would be important to me. Not the GPS heading which is generated by the direction the GPS receiver was being moved but the real magnetic compass heading. There are a few GPS receivers out there, one I found neat is the Wintec WSG-1000 (note, no SIRF III chip so if it works or not is unknown at the time!). But thinking about it, the heading only makes sense if the GPS receiver points into the same direction as the camera does. But that forfeits the entire idea of putting the GPS in the pocket and never look at it. So I had to say, given that restriction, what good for is the compass heading then? On the other hand, if the Unleashed module would have a magnetic sensor and mix its information into the GPS stream of data,......yeah, yeah, just dreaming. Sounds like a hell of development work, might get jammed by the camera electronics anyway and for this feature I would not spend a lot of money. But...dreaming...making something perfect.... But actually, who cares.
The other thing is the remote shutter. You have something that connects to the pins that operate the remote shutter, that thing has a wireless connection, so, can't that be used then? Would be kind of cool to open an application on the cell phone and operate the shutter from there, wouldn't it? I am not particularily sure it would make a lot of sense, certainly not for my needs but, well, you guessed it probably, ...making things perfect...philosophy...just for the sake of it. Development wise again I would guess it is rather difficult. The chip used right now is a serial to bluetooth converter. It will not support two bluetooth devices at the same time so you would need to build the bluetooth converter yourself, add some microcontroller, the module would probably grow in dimensions and price. Or we build a GPS unit with a release button, but then the advantage of using any new GPS module is gone.
Both features would be nice to have but for me, no thank you, not worth any additional costs.
Right now I am absolutely happy with the money spent, next thing I will look at is the XAiOX iTrackU DATALOGGER SiRF III. And hopefully even the GPS display on the camera will be perfect soon.