Testing two GPS loggers: thumbs up and thumbs down

If you're planning to turn your UAVs (or just R/C planes) into aerial mapping machines, you're going to want a GPS data logger. What they do is give position information that you can match with each of your shots, so you can properly align them into a mosaic and place it on Google Maps. Companies such as Pict'Earth can take a GPS log file and a zip file of a few hundred shots and turn them into a beautiful orthorectified Google Earth overlay like this.

I've used two GPS loggers: the i-Blue 747 Bluetooth device from Transytems, and the Trackstick II. The first I can recommend highly; the second I can't recommend at all. Here are the facts so you can make up your own mind.

1) The i-Blue 747 can be found for $70 at Amazon. It's got 16MB of memory, tracks 32 satellites and has Bluetooth so you can use it for real-time telemetry and even have it drive an autopilot. It comes with rechargeable lithium batteries and is really small (approx 2.9" x 1.75" x 0.75"). The software does all the basics, including letting you download a saved GPS session to Google Earth or a CSV text file and let you see satellite positions and current reading in real time.

[Note: the software communicates with the device via a virtual Com port, handled by a driver. It can be a little tricky to figure out which Com port, however, so I suggest you go to your Windows device manager and see which port was assigned to the device and set the software to use that. On one of my machines it was port 5; on the other it was port 10; it depends on how many other drivers you've already loaded.)


It also saves GPS positions once per second, which is important when you're trying to match it with pictures you're taking at least that fast. In our testing, it aquired a satellite lock in less than minute and was rock-solid in keeping it, even when we just tossed the device randomly into an aircraft's instrument bay, buried under other electronics and bathed with other radio emissions. Basically, we've used this devices on dozens of flights, UAV and otherwise, and its performance has been top-notch.

2) The Trackstick II costs nearly $150 at Amazon. It only has 1MB of memory and only tracks 12 satellites. No Bluetooth, so it's just a logger with no real-time function. It requires AAA batteries, and is long and rectangular, about twice the total size of the i-Blue (4.25" x 1.25" x 0.9"). It has a built-in USB jack, so you can plug it straight into your PC (the i-Blue requires a standard USB cable). The software does essentially the same thing as the i-Blue's.

In testing, three serious problems cropped up with the Trackstick (aside from it being expensive, big, and badly underfeatured):
  1. It only records a GPS record every 15 seconds in low-power mode and every 5 seconds in high-power mode. Even at the highest, battery-draining settings, that's way too slow for aerial mapping.
  2. It takes forever to get a satellite lock. The first time, it took more than half an hour and subsequently it took more than three minutes.
  3. Keeping that satellite lock is a struggle, too. By having a terrible GPS chip that only sees 12 satellites, the Trackstick II suffers from frequent drop-outs and glitchy datapoints. We found it essentially unusable.
Basically, I can't understand why the Trackstick is even sold. It does nothing that the i-Blue747 doesn't do at half the price, and doesn't do other important things like Bluetooth, 1-second GPS sampling, and having a useful amount of memory. I'm sorry I bought it--avoid.

Views: 1315


T3
Comment by icebear on September 23, 2007 at 11:49pm
Thanks Chris!
This is what I have been looking for to replace my Garmin Geko 201 as logger.
What is the weight of this unit (the i-Blue)?
Would it work to drive the Picopilot (RS-232 levels)?
Thanks,
/Bjorn

3D Robotics
Comment by Chris Anderson on September 24, 2007 at 10:03am
Bjorn,

I don't have it front of me so I can't tell you for sure, but it's light as a feather. Maybe the weight of a regular servo?

3D Robotics
Comment by Chris Anderson on September 24, 2007 at 10:17am
Oh, and to your other question, it only has USB and BT out (although it's RS232 internally), so I don't know how you'd connect it to the Picopilot directly.

T3
Comment by icebear on September 24, 2007 at 11:00am
Thanks Chris! Just ordered one, so I'll see what can be done, but if it is so light; I might as well use it stand alone...
Bjorn
Comment by fuhan on September 24, 2007 at 11:46pm
bjorn,
U ordered a i-Blue 747 for your picopilot?

I thought the picopilot already have a GPS receiver?

Rgds,
fuhan

Moderator
Comment by Gary Mortimer on September 25, 2007 at 10:37am
Sony have a logging gadget http://www.sony.co.uk/view/ShowProduct.action?product=GPS-CS1&site=odw_en_GB&pageType=Overview

I think I'm right in saying after you use it you sync it with the camera and it derives position, I've done no more than glance at the web page so could be wrong.

I have a Nikkai bluetooth GPS which works very well with my Nokia cellphone to send position via GPRS/3G that cost about $70 from Maplin here in the UK. Its not as feature packed as the i-Blue 747 that you mention.

It captures signals very quickly and even works really well in my house, I'm very impressed its much better than my old Garmin handheld.

Cheers

G

T3
Comment by icebear on September 26, 2007 at 12:50pm
fuhan,
I already have the Picopilot GPS but I was thinking of needing only one for logging AND navigation - however the 747 might be practical as a stand-alone I think.

Gary - thanks for the link!

Cheers,
Bjorn

3D Robotics
Comment by Chris Anderson on September 28, 2007 at 2:36am
Gary,

Thanks for the pointer to the Sony unit. Like the Trackstick, however, I think it's not appropriate for UAV use. It only tracks 12 sats and saves data points every 15 seconds. When you're taking pictures twice a second and the direction vector is important in properly placing the shot on a map, you need to sample GPS at least once a second. These little planes can bounce around a lot.

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