This is due to the bookkeeping of data bits which is handled in two places. The chan[ch].meas_bit_time is the data bit into the week the measurement was made. It is unambiguous but since it is on the user side of the interface it could be off by 1 bit. The other value "bit" comes from the data bit counter in the GP2021 and is accurate but ambiguous since it only counts up to 50 data bits and then rolls over. This part of the code resolves the ambiguity and corrects the meas_bit_time for later construction of the pseudorange.
>From: 姜毅 <
jiangyigirl@...>
>Sent: May 16, 2008 3:02 AM
>To:
opensource_gps@...
>Subject: [OpenSource_GPS] why tr_bit_time is different from 20ms epoch
>
> Dear Sir,
> In the function NavFix(), there is the program as follow:
> meas_bit_time_rem = chan[ch].meas_bit_time%50;
> if ( meas_bit_time_rem == bit+1 ) meas_bit_time_offset = -1;
> if ( meas_bit_time_rem == bit-1 ) meas_bit_time_offset = +1;
> if ( meas_bit_time_rem == 0 && bit == 49 ) meas_bit_time_offset = -1;
>
>I think transmit bit time is the same with 20ms epoch's value. However, sometime I found them are different. I wanna know why? Why meas_bit_time_offset is not equal zero? Why it shoud be -1,0,or 1? Is it can be more than -1,0,or 1, e.g 4,-4?
>
>I'm looking forward for your reply.
>Best Regards!
>
> Yours
>----- Original Message -----
>From: <
opensource_gps-request@...>
>To: <
opensource_gps@...>
>Sent: Friday, May 16, 2008 3:00 AM
>Subject: opensource_gps Digest, Vol 49, Issue 4
>
>
>> Send opensource_gps mailing list submissions to
>>
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>>
>> To subscribe or unsubscribe via the World Wide Web, visit
>>
http://lists.psas.pdx.edu/cgi-bin/mailman/listinfo/opensource_gps>> or, via email, send a message with subject or body 'help' to
>>
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>>
>> When replying, please edit your Subject line so it is more specific
>> than "Re: Contents of opensource_gps digest..."
>>
>>
>> Today's Topics:
>>
>> 1. Re: About pull_in state Parameter (??)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Thu, 15 May 2008 17:58:40 +0800
>> From: ?? <
jiangyigirl@...>
>> Subject: Re: [OpenSource_GPS] About pull_in state Parameter
>> To: <
opensource_gps@...>
>> Message-ID: <003501c8b672$4763d0f0$7001a8c0@dlmu7657b7f615>
>> Content-Type: text/plain; charset="gb2312"
>>
>> Dear Sir,
>>
>> I still wonder why we choose 45 deg as the threshold ?
>>
>> And I have another question. According to what ,you decide the bandwide of the code loop and carrier loop? Did you do some simulation? Would you send me something about the simulation?
>>
>> Thanks.
>>
>> Looking forward for your reply.
>>
>> Best regards
>>
>> Yours,
>> Jiang Yi
>>
>> ----- Original Message -----
>> From: "Clifford Kelley" <
cwkelley@...>
>> To: "??" <
jiangyigirl@...>
>> Sent: Tuesday, May 13, 2008 8:56 AM
>> Subject: Re: [OpenSource_GPS] About pull_in state Parameter
>>
>>
>>> The threshold for power is set at the sqrt of 2 times the rms value. To approximate this with integer values it was multiplied by 14 first and then divided by 10.
>>>
>>> 1200 was chosen as an approximate value of 45 deg based on the scaling used in the 4 quadrant arc tangent function.
>>>
>>> I hope this helps,
>>>
>>> Cliff
>>>
>>> -----Original Message-----
>>>>From: ?? <
jiangyigirl@...>
>>>>Sent: May 8, 2008 7:41 PM
>>>>To:
opensource_gps@...
>>>>Subject: [OpenSource_GPS] About pull_in state Parameter
>>>>
>>>>Dear Sir:
>>>>
>>>> I'm a graduate student. I'm very interested in OSGPS. I wanna know the detail about OSGPS.
>>>>
>>>>In the end of pull_in state, the software use if (c->avg > 14 * rms / 10 && c->th_rms < 12000 && c->ms_set) as the condition for track state.
>>>>
>>>>My problem :
>>>>1 avg > 14 * rms / 10 ,what's the meaning of 14 and 10
>>>>2 c->th_rms < 12000 why should we choose 12000 as the the threshold
>>>>
>>>>Looking forward for your reply!
>>>>Best Regard!
>>>>
>>>>
>>>>----- Original Message -----
>>>>From: <
opensource_gps-request@...>
>>>>To: <
opensource_gps@...>
>>>>Sent: Friday, May 09, 2008 3:00 AM
>>>>Subject: opensource_gps Digest, Vol 49, Issue 2
>>>>
>>>>
>>>>> Send opensource_gps mailing list submissions to
>>>>>
opensource_gps@...
>>>>>
>>>>> To subscribe or unsubscribe via the World Wide Web, visit
>>>>>
http://lists.psas.pdx.edu/cgi-bin/mailman/listinfo/opensource_gps>>>>> or, via email, send a message with subject or body 'help' to
>>>>>
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>>>>>
>>>>> You can reach the person managing the list at
>>>>>
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>>>>>
>>>>> When replying, please edit your Subject line so it is more specific
>>>>> than "Re: Contents of opensource_gps digest..."
>>>>>
>>>>>
>>>>> Today's Topics:
>>>>>
>>>>> 1. ???? (
shuaihan@...)
>>>>> 2. Re: Why add 0.5 in pull_in and track parameter (??)
>>>>>
>>>>>
>>>>> ----------------------------------------------------------------------
>>>>>
>>>>> Message: 1
>>>>> Date: Wed, 7 May 2008 12:00:42 -0700
>>>>> From: <
shuaihan@...>
>>>>> Subject: [OpenSource_GPS] ????
>>>>> To:
opensource_gps@...
>>>>> Message-ID: <
BAY0-MC10-F1057EBD7F68494E7B6E0E3A2D10@...>
>>>>> Content-Type: text/plain; charset="us-ascii"
>>>>>
>>>>> An HTML attachment was scrubbed...
>>>>> URL:
http://lists.psas.pdx.edu/pipermail/opensource_gps/attachments/20080507/78933d21/attachment.html
>>>>>
>>>>> ------------------------------
>>>>>
>>>>> Message: 2
>>>>> Date: Thu, 8 May 2008 09:55:09 +0800
>>>>> From: "??" <
jiangyigirl@...>
>>>>> Subject: Re: [OpenSource_GPS] Why add 0.5 in pull_in and track
>>>>> parameter
>>>>> To: <
opensource_gps@...>
>>>>> Message-ID: <000b01c8b0ae$8e56a420$7001a8c0@dlmu7657b7f615>
>>>>> Content-Type: text/plain; charset="iso-8859-1"
>>>>>
>>>>> Dear Sir:
>>>>>
>>>>> I found Open Source software is :
>>>>>
>>>>> pull_carr_C1=(int) (1.69852*Bnpullcarr/Carrier_DCO_Delta/(4.0+5.333*Bnpullcarr/1000.0+(1.8856*Bnpullcarr/1000.0)*
>>>>> (1.8856*Bnpullcarr/1000.0))+0.5);
>>>>>
>>>>> pull_carr_C2=(int) (0.6369183/Carrier_DCO_Delta*(1.8856*Bnpullcarr/1000.0)*(1.8856*Bnpullcarr/1000.0)*1000.0/
>>>>> (4.0+5.333*Bnpullcarr/1000.0+(1.8856*Bnpullcarr/1000.0)*(1.8856*Bnpullcarr/1000.0))+0.5);
>>>>>
>>>>> pull_code_C1=(int) (10.598/Code_DCO_Delta*Bnpullcode/(4.0+5.333*Bnpullcode/1000.0+(1.8856*Bnpullcode/1000.0)*
>>>>> (1.8856*Bnpullcode/1000.0))+0.5);
>>>>>
>>>>> pull_code_C2=(int) (4.028/Code_DCO_Delta*(1.8856*Bnpullcode/1000.0)*(1.8856*Bnpullcode/1000.0)*1000.0/
>>>>> (4.0+5.333*Bnpullcode/1000.0+(1.8856*Bnpullcode/1000.0)*(1.8856*Bnpullcode/1000.0))+0.5);
>>>>>
>>>>> I know C1 C2 is
>>>>> pull_carr_C1 = 1/(Ko*Kn)*8*zeta*On*Ts/(4+4*zeta*On*Ts+(On*Ts)^2);
>>>>> pull_carr_C2 = 1/(Ko*Kn)*4*(On*Ts)^2/(4+4*zeta*On*Ts+(On*Ts)^2);
>>>>>
>>>>> By compared, I wonder why add 0.5 to C1 and C2
>>>>>
>>>>>
>>>>> ----- Original Message -----
>>>>> From: <
opensource_gps-request@...>
>>>>> To: <
opensource_gps@...>
>>>>> Sent: Thursday, May 08, 2008 3:00 AM
>>>>> Subject: opensource_gps Digest, Vol 49, Issue 1
>>>>>
>>>>>
>>>>>> Send opensource_gps mailing list submissions to
>>>>>>
opensource_gps@...
>>>>>>
>>>>>> To subscribe or unsubscribe via the World Wide Web, visit
>>>>>>
http://lists.psas.pdx.edu/cgi-bin/mailman/listinfo/opensource_gps>>>>>> or, via email, send a message with subject or body 'help' to
>>>>>>
opensource_gps-request@...
>>>>>>
>>>>>> You can reach the person managing the list at
>>>>>>
opensource_gps-owner@...
>>>>>>
>>>>>> When replying, please edit your Subject line so it is more specific
>>>>>> than "Re: Contents of opensource_gps digest..."
>>>>>>
>>>>>>
>>>>>> Today's Topics:
>>>>>>
>>>>>> 1. osgps run under windows xp (yuguangzhan)
>>>>>>
>>>>>>
>>>>>> ----------------------------------------------------------------------
>>>>>>
>>>>>> Message: 1
>>>>>> Date: Wed, 7 May 2008 12:05:10 +0000 (UTC)
>>>>>> From: yuguangzhan <
yuguang.zhan@...>
>>>>>> Subject: [OpenSource_GPS] osgps run under windows xp
>>>>>> To:
opensource_gps@...
>>>>>> Message-ID: <
loom.20080507T120323-538@...>
>>>>>> Content-Type: text/plain; charset=us-ascii
>>>>>>
>>>>>> Hi, Cliff:
>>>>>>
>>>>>>
>>>>>> I purchased a GPS1005 PCI bus board on year 2007 from GPS Creations. Now we
>>>>>> want to run it under windows xp.So we wonder if the opensource_gps code can
>>>>>> run in windows xp and if there is a windows WDM driver available.
>>>>>>
>>>>>> Could you please advise how could I proceed in order to find
>>>>>> such driver? Do you know anyone else who could have it available?
>>>>>>
>>>>>> Sincerely,
>>>>>>
>>>>>> yuguang.
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> ------------------------------
>>>>>>
>>>>>> _______________________________________________
>>>>>> opensource_gps mailing list
>>>>>>
opensource_gps@...
>>>>>>
http://lists.psas.pdx.edu/cgi-bin/mailman/listinfo/opensource_gps>>>>>>
>>>>>>
>>>>>> End of opensource_gps Digest, Vol 49, Issue 1
>>>>>> *********************************************
>>>>>
>>>>> ------------------------------
>>>>>
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>>>>>
>>>>> End of opensource_gps Digest, Vol 49, Issue 2
>>>>> *********************************************
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