Is the sirf starlll chip really a 20 channel

[+EraSeek]

Is the sirf chip really a 20 channel chip in a 12 channel unit, and do the use static navigation as talked about in this article?

http://www.pocketgpsworld.com/bt338.php

[+Steel City Seekers]

Apologies I offer, but I only breezed through the article you posted. I've used a different SirfIII than you cited. That is, I've used a Haicom HI-303III instead of the 338 featured in this article.

 

It is my understanding that my Haicom does indeed use static navigation and that it is a 16 channel. In fact, I thought all Sirf III receivers were minimum 16 channel.

 

I've experienced some of the attributes mentioned in the article, such as an extraordinarily fast acquistion time. On the order of one second is not unusual for me.

 

But I'm not sure what you're asking. Are you asking if they're all static navigation? I don't know the answer to that. Are you asking if they are all 20 channel? Again, I thought the min. was 16, and I'm pretty sure mine is a 16 channel.

[+EraSeek]

I have a Garmin 60cx. It has the sirf chip. In this article it states that the chip is 20 channel. My unit is listed as the normal 12 channel reciever. How do I understand the difference in this information.

The article also states that the chip uses static navigation (this could be a problem), but it is disable in some units. Is it used in the Garmins or not? "Static navigation" is "not" navigating!

[+Train_Man]

I think the chip is 20 channel so the chip tracks 20 but the unit can only actually calculate 12 channels so it uses the strongest 12 that it has. This means it is slightly better than a standard 12 channel unit but not a lot better.

 

Don't quote me on this one but that is my understanding.

[+EraSeek]

Bump.

[MrMullen]

I think the chip is 20 channel so the chip tracks 20 but the unit can only actually calculate 12 channels so it uses the strongest 12 that it has. This means it is slightly better than a standard 12 channel unit but not a lot better.

 

Don't quote me on this one but that is my understanding.

 

Is it pointless that a Sirf chip can support 20 satellites at once? If GPS has 24 (21 in services and 3 spares) satellites, then that means only 12 are on your side of the planet at once and probably only 10 of those are viewable. If this is true, then what is the point of being able to process data for something that is not even possible?

[+budd-rdc]

I agree that having support for 20 channels might be unnecessary. I have a Lowrance iFinder GO with 16 channels, and most satellites it has seen at one time was 13 non-WAAS satellites (14 total) so far. I keep wishing this unit has a SiRF III, but no one has any definitive information on that.

 

It would be nice if Garmin and others can tell us why they don't use all the channels available. Conserving processing power seems like a logical reason.

[+Train_Man]

I think the reason they don't is this: You could track 16 sats while making the gps refresh rate 1/2 second lower while getting maybe 6" better accuracy 25% of the time or you can have the response of the unit faster.

 

I'd rather have a fast unit.

[+jotne]

SiRF Star III support using 20 satellites, but you will not get so many at the sky at one time.

 

More info here:

http://www.sirf.com/Downloads/Collateral/GSC3(f)_6.20.05.pdf

[+Boardslider]

SiRF Star III support using 20 satellites, but you will not get so many at the sky at one time.

 

 

Perhaps a rare case of forward compatibility?

[+jotne]

Galileo will be fully operational in 2010. I do not know if today’s GPS can see these satellites, or if we need new hardware.

[ossumguywill]

This could be two things. Either SirfIII is compatible with satellites planned for the future (like Galileo) or it is just a hoax to get you to think it is better than other units. However, I would like to mention that North america usually has at least 12 satellites over it and sometimes around 16.

[capt caper]

Is the sirf chip really a 20 channel chip in a 12 channel unit, and do the use static navigation as talked about in this article?

http://www.pocketgpsworld.com/bt338.php

 

I'd like to know if the 60CSX uses the static navigation as well.

 

I read that one way it effects us is that if you stop then go slowly it won't show you moving for a time. I would assume you would notice delays in the compass arrow,etc. as well when you stop and go alot in your using the gpsr.

 

They do that I guess so it keeps it jumping all over the place as the chipset is sensitive

[kerecsen]

I'd like to know if the 60CSX uses the static navigation as well.

 

I read that one way it effects us is that if you stop then go slowly it won't show you moving for a time. I would assume you would notice delays in the compass arrow,etc. as well when you stop and go alot in your using the gpsr.

 

They do that I guess so it keeps it jumping all over the place as the chipset is sensitive

 

Yes, that is indeed the case. For car navigation, and in the case of the Sirf II chipset, it was a better compromise to sacrifice low-speed behavior to reduce jumpiness. In fact, many of the 60c(s)x owners complain about how the GPS "wanders" while they are standing still (but would also object to a loss of low-speed resolution, I'm sure )

 

In general the Sirf III is good enough that static navigation is not worth using; in fact hardly any manufacturer has it enabled by default.

 

As for the 20 channel thing: the Sirf III is built on the principle of trying to grab as much signal data as possible, even if those signals are reflected or they don't fit with the current speed/position assumption, and then using a massively parallel calculation unit to try to figure out the most likely solution based on all that data. The "extra" channels that aren't actively tracking satellites are used to search for other potential signals that may it be doppler-shifted, reflected or coming from a barely visible satellite.

The biggest benefit of the extra channels is realized during a cold start, where the GPS has to experiment a lot before it comes up with an initial speed/position/time assumption.