Re: ??: code tracking

Yes, you are right. However, the receiver can still
give you accurate position solutions with 1/4 chip
offset in time estimates. As far as it stationary
or moving slowly, it doesn't really cause any problem.

Tak

--- [email protected] wrote:
> 
>     Thank you,Cliff,
>               
>              I'd like to continue the question:
>               Since  The prompt arm looks like a
> late arm thus the  loop will lock 1/4 chip early of
> the "real" code phase
>               then when we calculate transmit time
> from code phase,we should subtract 1/4 chip from the
> code phase we get from GP2021.
>                Right?
> 
> 
>    Zhu Di 
> 
> 
> -----????-----
> ???: Clifford Kelley [mailto:[email protected]]
> ????: 2004?5?21? 12:40
> ???: Di Zhu (Beijing); [email protected]
> ??: Re: code tracking
> 
> 
> Dear Zhu Di,
> 
> You will notice in chan_allocate() and in
> cold_allocate()
> this statement:
> 
>       ch_cntl(ch,prn_code[prnn]|0xa000);
> 
> 
> 0xa000 sets the high order bits as    15  14  13  12
>  11  10
>                                                     
>    1    0    1    0
> 0    0
> 
> bit 15 sets it for GPS
> bits 14 & 13 set the track select to late code
> bit 12 sets the update mode
> bit 11 sets the code to on
> bit 10 sets the source as sign0 and mag0
> 
> So the difference between prompt and late, not
> dithering.
> 
> 
> I hope this helps,
> 
> Cliff
> 
> ----- Original Message ----- 
> From: <[email protected]>
> To: <[email protected]>; <[email protected]>
> Sent: Thursday, May 20, 2004 9:00 PM
> Subject: ??: code tracking
> 
> 
> 
>       Hi,Tek and Cliff:
> 
>            sorry,I still cann't understand why
> that's a early-minuts-late
> discriminator
> 
>            I understand it in this way :
>            the tracking arm is set to dithering
> mode, It will output
> accumulated data as : 1/2 chip early correlation,1/2
> chip late
> correlation,1/2 chip early corrlation,.....and son
> on
>           the prompt arm will output accumulated
> data: prompt
> corrlation,prompt correlation,prompt
> correlation....and so on.
>          Then,we use "dreq=
> trk_code_k*(prompt_mag-dith_mag)"
>           we get
> dfreq=trk_code_k*(rss(prompt,prompt,prompt...
> )-rss(early
> +late+early+late,... ) );
>           so, I cann't see it's means
> early-minus-late.
> 
>           pls give me a help!
>           Thanks!
> 
>         Zhu Di
> 
> 



	
		
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