Quote:
Originally Posted by ahhbeebee
From what I gather, the newer technology (SiRF Star III) is the best available for the USB/Bluetooth type units. Is reception very good? Will there be 'blindspots' in certain areas/terrain?
SirfstarIII is the minimum you would wish to purchase today. There is a newer technology just beginning to appear but there isn't enough experience in the field to demonstrate whether it's really better or enough better to be worth looking for.
We are talking about radio signals that are extremely weak to begin with. So there are always going to be situations where even the best combination of antenna and receiver chipset and placement will fail to get a fix.
I have a five year old handheld (Garmin iQue 3600), the Pharos 500 USB receiver that comes with Microsoft Streets&Trips and the i.Trek M7 combo Bluetooth/USB receiver. Both of the standalone receivers have SirfStarIII receivers in them. In the field they will both get a fix in situations where the older technology of my handheld (unaided) will not. If I connect an external antenna to my handheld, it will normally get as good a fix in those same situations, but it will still take longer, sometimes much longer, to get a lock on enough satellites to get a fix.
I use my handheld in a dash mount for navigation in the car. I don't have room for my laptop so I have not used it very much for in-car navigation. It happens that today I took a trip out of town about an hour or so each way and since I was running solo I decided to fire up the laptop on the seat beside me as well as the handheld in its usual mount. I ran the laptop with the i.Trek M7 in Bluetooth mode and Garmin's Mobile PC on the laptop going out, and the M7 with Garmin's nroute on the laptop coming home.
I didn't bother to try the Pharos USB receiver because the only place I could put my laptop was on the seat beside me and the cable on the Pharos was not quite long enough to let me put it on the dash.
Based on today's experience, I know that my personal choice, if I was going to be able to use my laptop in the vehicle, would be to get a nice Bluetooth unit, no contest at all. They are not expensive and they give you complete flexibility of placement of both the receiver and laptop, independently from one another. I especially like the M7 combo unit because you don't need any special battery charging arrangements. You can just plug it into the USB port on the laptop any time you are on the computer and the M7 will charge right up.
As for the on-road experience, the M7 got a lock quicker than my older technology handheld. But that turned out to be academic because the time it took to get the laptop booted and the nav software running was orders of magnitude longer. With the handheld I can just start driving and it will soon enough get a lock so it doesn't delay me at all. With the laptop it is not reasonable to do anything with the vehicle at all until the laptop is booted and the nav software is running.
The satellite signals were much stronger on the M7 with its newer technology but that turns out to be mostly academic in my situation. As long as the signal is good enough for a lock on enough satellites to give you a good fix, any stronger signal strength is mostly irrelevant. I say "mostly" because I live out on the prairies where satellite visibility is rarely an issue. In situations where satellite visibility is an issue, the stronger signal reception gives a wider margin for dealing with more difficult situations. It will also usually mean you can get a lock on more satellites in more difficult situations. That normally means better accuracy.
It turns out that, in normal road navigation, accuracy is also a somewhat overrated issue, within reasonable limits. As long as the device is able to keep you on the correct roadway and gets you within visual distance of your destination you don't need any more accuracy than that. However, if you are going to do serious geocaching, accuracy is a much bigger issue. Handhelds are great for geocaching; laptops not so much.
Sorry for rambling. I hope some of that is useful, or at least interesting. It's mostly obfuscation to hide the fact that although I'm keenly interested in laptop navigation software I really don't find the laptop very useful for on-road navigation in my personal situation, so I don't have a lot of practical usage experience. Don't get me wrong; I would dearly love to be able to have Garmin Mobile PC's drop-dead gorgeous nav display on that gigantic 15" screen hanging somewhere in easy view. It's just not going to happen in my mini-SUV or my wife's Mazda3. So I'll keep nursing the iQue 3600 along until it dies, in hopes that someone will get around to building something equally competent before it does.
...ken...