[Liverpool] USB GPS receivers

[Sebastian Arcus]

Hi all,

I'm not sure if there is any interest in this, but during my work to add 
gps tracking to the cctv bus system, I had to test several usb gps 
adapters because of variation in behaviour by some of them. The main 
point of my research so far seem to be that the adapters based on the 
SirfStar III chipset (which covers a good majority of models available) 
are pretty low quality. They take a long time to get a fix - specially 
if they haven't been used in the last 24 hours and have to re-download 
data from the satellites. On cloudy days - some of them can take 30-40 
minutes to obtain the first fix.

I have enquired on the gpsd mailing list (which, by the way, I wouldn't 
call "friendly" to say the least). I haven't really obtained much 
information. They mostly seem to be involved with the "embedded" market 
- not entirely sure what they mean by that. I could assume they really 
work for various gps manufacturers - which would explain the really 
abrupt attitude and at times disguised hostility towards the Linux 
kernel and tools.

To cut the story short - I am now the proud owner of 6 gps adapters. The 
bottom line (and useful conclusion) is that the BluNext BN-903S adapter, 
based on the Adopt SkyTraq Venus 6 chipset seems to be an excellent 
piece of hardware. You can just plug it in, and it gets a fix within at 
worst 2-4 minutes, if you are in between buildings, on a cloudy day, and 
it hasn't been used for few days. Otherwise, it will get a fix in a 
matter of seconds.

The funny thing is that this is the cheapest adapter of all I bought - 
£16.95 on Amazon.co.uk with free delivery. It has 65 channels (can 
listen to 65 satellites at the same time, although I doubt the current 
constellation has that many satellites anyway) - versus 20 channels for 
the SirfStar III chip. I'm not sure how much difference that makes in 
practice, but whatever the reason, it works brilliantly.

On the other hand, the SirfStar III is always referred to in glowing 
terms on all websites I've seen adapters for sale. Go figure. Either 
their marketing machine is one great contraption, or I'm the unlucky 
owner of 3 different adapters from different manufacturers with their 
chipset in them - all of them naff.


In case somebody will find the above useful.

If anybody else on the list is using usb, serial or bluetooth gps 
receivers with a computer, I'd be curious of their point of view. 
Performance of adapters in smartphones might be a little bit skewed, as 
lots of them also use AGPS over Internet, which makes the the quality of 
the actual chip more difficult to assess solely on its gps reception merits.

Hope you are all keeping well,


Sebatian