Ceril

Hi all,

I received a recommendation to get a GPS receiver based on the MTK chipset as opposed to the MTK one. I found very little in the way of reviews on the net (Google didn't help me too much this time).

I understand that it uses less battery power and supposedly is accurate to 5m as opposed to the SiRF III which is accurate to 10m. At least that is the line.

I am specifically looking at the globalsat BT-821 (or is it 812?) and I cannot find reviews. Equally in my neck of the woods it is half the price of the globalsat SiRF III model (i forgot the number), so it makes me wonder if indeed it is a good buy......

I found a suggestion by the folks at buygpsnow.com that MTK and SiRF III are generally the same plus minus the battery life and a slightly quicker cold pick up for the MTK - but they mention the 51 channel version specifically. The BT821 is 32 channels but the globaltop G66 is 51 channels. Is there really a difference?

Any and all recommendations are very very welcome.

And links to reviews if *YOU* find them! :)

Thanks

JakeRich

Accuracy has little to do with channels. Accuracy is determined by the constellation of satellites (DOP or Dilution of Position) and whether or not you receive any differential GPS signals (DGPS, or WAAS). Most of the time the constellation is good enough to get a good fix, although when a satellite sets or rises the long atmospheric path can induce some pretty wild swings as the signal degrades. DGPS or WAAS is a mechanism that reduces error by computing the error at a known fixed location and then communicating that error as a correction to GPS receivers in the area. Any receiver with the capability for WAAS and who is actually receiving valid WAAS data will have the error cut from 12-15M to 3-5M 95% of the time.

Ceril

Thanks for the info (X2). I was having difficulties finding any good information (from a non-commercial source) about the MTK chip set and its performance. I found some places in general. I ended up going for the G66 because I found a sale which lowered it to price levels similar to the US (usually we are quite a bit above). I will report back what happened.

deeinlondon

so Ceril - can we have an update on the GPS you bought

Ceril

oops. indeed I forgot to report back.
ok, well the g66 is a sexy little device. Very sleek. Really thin and light. I mean really.

First I will start with the package. You get a car lighter outlet to miniusb cord, a CD with trial software, and the unit itself. What was lacking is some kind of protective case/carrying case. I have a couple cases lying around at home, but nothing that I can say "fits it like a glove". It does have a lanyard loop, so if that's your thing....

The unit charged quickly (though I used a regular usb to mini-usb associated with my computer to do the first charging.)

The lights in the day light are a bit hard to see. It is not always clear if the satellite signal is operating (it blinks once per 20-30 seconds when it is connected) and it is a pale white color. The power button is a bit funky and not so easy to turn on and off. Though it writes that it is a "touch" i find it is more of a long press. and it is not once or even twice that i found it "on" after I had turned it "off".

The connection on a subjective basis is very fast - at least as fast as the sirf III that I used earlier (OnCourse BT - if forgot the number) if not faster. I never had a problem with losing the signal with my sirf and not with this. I don't know how to measure these things and I don't know of any utilities which can meaure it. I also expect that if you live in singapore, upstate new york, london or someplace else, that the avaliability of the satellites can change a bit, so my measure here might not exactly be right for you where you live.

Every forum i chacked in regards to the 51 channels vs. fewer always critisized the availability of the greater number of channels. I don't see the need for this critique. It is true that there isn't a way that you will fill even half of the channels, but it also doesn't cost more or bother the function of the channels that exist. In my view, it is just a description which doesn't affect function.

In regards to battery - I haven't really challenged it. The official stats are 6 hours. I always have the charger with me in the car, so it is hard for me to consider that I will have a problem. Sorry that I cannot be more fo help here.

Overall, I think that no one loses from using an MTK based receiver, and can even benefit. I am not sure that this specific receiver is the best one, but it certainly is a good one to very good.

Ceril

oh, i forgot. I am not sure if the unit actually does run at 5hz (checks and changes position 5 times per minute as opposed to 1 time per minute) and my mails to igo (the software I am currently using) have gone unanswered in regards to compatibility. I'd be interested to hear from others how to solve the question.

deeinlondon

The only things I've found on the internet are that Sirf III may be better for walking whilst the MTK is a bit better for driving

But also that the MTK uses a lot less power so you can find a lot of very small unit that use this chipset as they require a much smaller battery to last as long as a Sirf III unit.

I mainly want a tiny BlueTooth GPS Unit I can have in my pocket and navigate using my Nokia Mobile with Google Maps or Nokia Maps whilst walking in cities.

Ceril

if small is what you want, then i think the g66 would fit. it is about the size of a credit card in width and length...maybe a slight bit more. it is thinner than a pack of trident gum. it is also very light - so the fact that you would put it in your shirt pocket indeed fits the use to a "t". I don't walk with the gps or do geocaching, so i don't have a lot to add in those regards. i think the unit could fit your needs.