This is one of the latest releases from GlobalSat, and it certainly lives up to expectations. The results were very nice, and the unit outperforms the LeadTek CF 9534 unit I reviewed last year, mainly because of the use of the SiRFstar III chipset.
The SiRFstart III is the same chip used in the fabulous GlobalSat BT-338 I reviewed and compared around the same time as the LeadTek CF 9534. This chipset is well known for its fast "Time To Fix", with a cold start of 42 seconds, warm start of 38 seconds, hot start of 1 second and a reacquisition time of 0.1 seconds.
This unit has a single red LED which is solid when on and searching, and flashing when a fix has been obtained - valuable confirmation of the operational status of the hardware.
The unit I received for review came with a PCMCIA to CF adaptor card, for use with laptops, and a 5 metre long magnetic based external antenna which can plug into the right hand side of the receiver. These are listed as optional extras, so check when you purchase.
I didn't feel the need to use the antenna during any of my evaluation however as the unit performed well on its own, even inside my car. I did try it out, but the improvement was marginal. The antenna may be useful however in some situations with coated windscreens, in trucks, boats, etc..
Without using the external antenna, the Globalsat BC-337 was fast to pick up 3 or 4 satelintes from within my lounge within 45 seconds from a cold start. The initial fix was a bit variable, but it continued to pickup plenty of additional sattelites over the next few minutes, and the fix stabilised right on target at stayed that way, consistent with the BT-338.
The manufacturer claims 5-10 meter accuracy, which seems consistent with my observations as the unit could track me from one side of our deck to the other. They also say the unit can do single satelite updates in reduced visibility, has superior urban canyon performance, and a foliage lock for weak signal tracking.
During one drive through the urban canyon of The Terrace here in Wellington, the unit tracked reasonably well. But whilst staying stationary for a while in the thick of the tall buildings, the reflected signals still managed to play havoc with the location engine, and my reported fix moved around a fair bit. Once I started moving again, the accuracy returned.
A problem with plug-in GPS units in general is that the unit is switched off when the PDA is switched off. Not keeping the GPS unit powered doesn’t give the chipset a chance to refine, optimize, and track weaker sattelite signals, and means you have to wait for the unit to reacquire its fix each time you wish to simply check your location (say, when hiking). A rechargeable battery onboard would be an improvement, giving the ability to leave the GPS unit on and tracking even when your PDA device is switched off. The unit is stated to use about 90mA of power, so a pretty low drain on batteries, but still could reduce PDA operating times by up to 20% since the PDA itself needs to be on to power the card device.
Also, if you only have a single slot on your PDA, then you will have to rely on internal PDA memory for your actual maps, as no external card storage will be available. GlobalSat have brought out a SD slot GPS unit with onboard memory for maps, so I expect this will become more common over time. My iPAQ hx4700 has plenty of onboard memory, plus an SD slot, so this was not an issue for me (though the CF GPS unit prevented inserting/removing the SD card as they are side by side).
Overall, one of the nicer GPS receivers I have reviewed, comparable with the BT-338. Which model you choose to use will really depend on the device you want to use it with. The BT-338 will offer a bit more flexibility in this regard, but is more expensive and you need to keep it charged. This CF based unit is a no-fuss, reliable, and accurate solution, and since I have CF on my PDA, is my preferred carry-around unit currently.
