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From: JF Mezei on 28 Mar 2010 03:32
Alan Baker wrote:

> All the satellites transmit on the same frequency.

But are not received at the same frequency.


> Complete and utter nonsense. Compared to the speed of light, *nothing*
> in the system is moving "at a significant speed".

doppler effect is significant at speeds the satellites travel in orbit,
and are amplified at walking speeds (because you may be walking towards
one satellite while walking away from another).

Read on on real GPS. Doppler is a very significant portion of
calculations and what frequency a signal is received at is a large part
of how a GPS calculates not only your position but your speed and
direction of travel.



> The GPS system uses code division multiple access to receive information
> from all satellites in the system on two frequencies. The doppler shift
> plays no role in picking up a particular satellites transmissions.

I suggest you read up on it. It does.
From: Alan Baker on 28 Mar 2010 03:39
In article <4baf0615$0$1485$c3e8da3(a)news.astraweb.com>,
JF Mezei <jfmezei.spamnot(a)vaxination.ca> wrote:

> Alan Baker wrote:
>
> > All the satellites transmit on the same frequency.
>
> But are not received at the same frequency.
>
>
> > Complete and utter nonsense. Compared to the speed of light, *nothing*
> > in the system is moving "at a significant speed".
>
> doppler effect is significant at speeds the satellites travel in orbit,
> and are amplified at walking speeds (because you may be walking towards
> one satellite while walking away from another).
>
> Read on on real GPS. Doppler is a very significant portion of
> calculations and what frequency a signal is received at is a large part
> of how a GPS calculates not only your position but your speed and
> direction of travel.
>
>
>
> > The GPS system uses code division multiple access to receive information
> > from all satellites in the system on two frequencies. The doppler shift
> > plays no role in picking up a particular satellites transmissions.
>
> I suggest you read up on it. It does.

Let's see some quotes and references....

--
"The iPhone doesn't have a speaker phone" -- "I checked very carefully" --
"I checked Apple's web pages" -- Edwin on the iPhone
"It is Mac OS X, not BSD.' -- 'From Mac OS to BSD Unix." -- "It's BSD Unix with Apple's APIs and GUI on top of it' -- 'nothing but BSD Unix' (Edwin on Mac OS X)
'[The IBM PC] could boot multiple OS, such as DOS, C/PM, GEM, etc.' --
'I claimed nothing about GEM other than it was available software for the
IBM PC. (Edwin on GEM)
'Solaris is just a marketing rename of Sun OS.' -- 'Sun OS is not included
on the timeline of Solaris because it's a different OS.' (Edwin on Sun)
From: JF Mezei on 28 Mar 2010 03:56
Alan Baker wrote:
The doppler shift
>> > plays no role in picking up a particular satellites transmissions.
>>
>> I suggest you read up on it. It does.
>
> Let's see some quotes and references....
>

I tell you what, you can find out by yourself. There is this neat web
site operated by Mr Google:

http://www.google.com and you type in the word GPS and the word DOPPLER
with a space in between the two and press "GOOGLE SEARCH" button


Here is a hint of things you will find:
Doppler Shift of Satellite Frequency Correction
The GPS receiver must shift tuning by the calculated doppler shift
to detect the satellite signal. The amount is from 0 to about 2400 Hz.
From: Alan Baker on 28 Mar 2010 04:02
In article <4baf0bbe$0$13661$c3e8da3(a)news.astraweb.com>,
JF Mezei <jfmezei.spamnot(a)vaxination.ca> wrote:

> Alan Baker wrote:
> The doppler shift
> >> > plays no role in picking up a particular satellites transmissions.
> >>
> >> I suggest you read up on it. It does.
> >
> > Let's see some quotes and references....
> >
>
> I tell you what, you can find out by yourself. There is this neat web
> site operated by Mr Google:
>
> http://www.google.com and you type in the word GPS and the word DOPPLER
> with a space in between the two and press "GOOGLE SEARCH" button

Sorry. Not my job to support your claims for you...

>
>
> Here is a hint of things you will find:
> Doppler Shift of Satellite Frequency Correction
> The GPS receiver must shift tuning by the calculated doppler shift
> to detect the satellite signal. The amount is from 0 to about 2400 Hz.

What you haven't proven is that it needs any help from knowing its
location to do this...

It almost looks like you're the one who decided what is what just by
typing "GPS DOPPLER" in Google...

--
"The iPhone doesn't have a speaker phone" -- "I checked very carefully" --
"I checked Apple's web pages" -- Edwin on the iPhone
"It is Mac OS X, not BSD.' -- 'From Mac OS to BSD Unix." -- "It's BSD Unix with Apple's APIs and GUI on top of it' -- 'nothing but BSD Unix' (Edwin on Mac OS X)
'[The IBM PC] could boot multiple OS, such as DOS, C/PM, GEM, etc.' --
'I claimed nothing about GEM other than it was available software for the
IBM PC. (Edwin on GEM)
'Solaris is just a marketing rename of Sun OS.' -- 'Sun OS is not included
on the timeline of Solaris because it's a different OS.' (Edwin on Sun)
From: JF Mezei on 28 Mar 2010 04:48
Alan Baker wrote:

> What you haven't proven is that it needs any help from knowing its
> location to do this...

Given its approximate location and time, the GPS receiver uses its
stored almanach to determine which satellites SHOULD be overhead right
now, and more importantly, which ones are approaching and which ones are
moving away to calculate the doppler shift so it knows at what frequency
to listen to to see whether it gets a signal from that satellite.

This is why position acquisition is very rapid when you turn on the unit
and it hears satellites it expected to hear, and at the frequencies it
had calculated they would be.

But when this doesn't happen, the GPS receiver listens for any satellite
on the full range of frequencies where it could expect signals (aka, the
2400hz doppler shift on either side of the main frequency). And this
takes longer to happen.

> It almost looks like you're the one who decided what is what just by
> typing "GPS DOPPLER" in Google...

Many years ago, while learning GPS on my GPS II+, (you appear young
enough that perhaps you weren't born 12 years ago), I also didn't quite
believe about doppler, but is is a significant portion of GPS
calculations. The GPS satellites are NOt geostationary. So they are in
constant relative movement versus any one point on the planet. Don't
remember what their obital frequency is (but is many hours), their
orbital altitude is about half of a geosynchronous orbit.

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