[teqc] Signal/Noise values from Z-Extreme receiver data

Lou Estey lou at unavco.org
Tue Jul 20 10:24:57 MDT 2004


Frank.Pache at leica-geosystems.com wrote:

> Hello Lou,
> 
> regarding the infos mentioned below on the Trimble sensor.
> What do you consider an 'old' and what is a "new" Trimble sensor?
> 
> Regards/Gruß,
> Frank

In order to maintain the thread, I'll reply to the list.
AFAIK:

Trimble receivers that use AMU:
	series 4000 thru SST, SSE, SSi

Trimble receivers that use dBHz:
	4700
	5700
	NetRS, R7

I don't know where the 7400, 4400, 4600, 4800, 5800, R8 fall.

--lou

> ----- Forwarded by Frank Pache/CHHER/Central/Leica on 20.07.2004 17:57
> -----
>                                                                                                                                 
>                       Lou Estey                                                                                                 
>                       <lou at unavco.org>         To:       teqc at unavco.org                                                        
>                       Sent by:                 cc:                                                                              
>                       teqc-bounces at ls.u        Subject:  Re: [teqc] Signal/Noise values from Z-Extreme receiver data            
>                       navco.org                                                                                                 
>                                                                                                                                 
>                                                                                                                                 
>                       20.07.2004 16:00                                                                                          
>                       Please respond to                                                                                         
>                       teqc support                                                                                              
>                                                                                                                                 
>                                                                                                                                 
> 
> 
> 
> 
> Dario,
> 
> 
>>I received a large set of TEQC Rinex translated files from receivers
>>ASHTECH-ZXII y Ashtech Z-Extreme.
>>
>>I found in all files that Rinex files from ASHTECH Z-XII files have
>>"normal" S/N values, but Rinex files from Z-Extreme receivers have
>>inusual low values.
>>
>>Here is an example:
>>
>>*** fragment of 0101323a.obs (ASHTECH-Z12) ***
>>
>>     2.10           OBSERVATION DATA    G (GPS)             RINEX
>>VERSION / TYPE
>>teqc  2000Feb29                         20031126 18:30:14UTCPGM / RUN BY
> 
> / DATE
> [...snip...]
> 
>>03 11 19 16 53 15.0000000  0  6G31G25G 3G20G11G14
>>    163881.32049    121992.80947  20614307.799    20614316.657
> 
> 20614307.412
> 
>>   -135169.76049    -99226.04645  23476649.000    23476663.221
> 
> 23476649.744
> 
>>    401236.84149    291232.02346  22088848.354    22088861.183
> 
> 22088848.818
> 
>>    -47342.94949    -34561.55546  22833207.043    22833219.599
> 
> 22833206.840
> 
>>   -150271.80449   -109618.26847  21851897.708    21851905.008
> 
> 21851896.847
> 
>>    352130.13149    241932.75946  22364268.146    22364278.171
> 
> 22364268.989
> 
> 
>>*** fragment of 0701322b.obs (Z-Extreme) ***
>>     2.10           OBSERVATION DATA    G (GPS)             RINEX
>>VERSION / TYPE
>>teqc  2000Feb29                         20031126 18:31:57UTCPGM / RUN BY
> 
> / DATE
> [...snip...]
> 
>>03 11 19 16 53 15.0000000  0  8G 1G31G14G11G15G 3G20G25
>>  -2727568.31443  -2054893.07342  24332321.138    24332341.154
> 
> 24332321.645
> 
>> -17569012.83643 -13641080.70642  20508584.291    20508594.406
> 
> 20508585.718
> 
>> -14182208.39943 -11007367.76742  22228090.048    22228101.811
> 
> 22228092.867
> 
>> -16590976.58643 -12893430.70842  21736040.151    21736048.901
> 
> 21736041.451
> 
>>   -169784.17243    -83278.68442  24298154.772    24298172.032
> 
> 24298154.260
> 
>> -12586189.95443  -9802697.97242  21980369.384    21980381.242
> 
> 21980370.239
> 
>> -10854547.65943  -8415804.11442  22732908.967    22732921.839
> 
> 22732909.781
> 
>>  -8885066.75443  -6887797.97942  23349973.796    23349991.605
> 
> 23349976.198
> 
> 
>>I pick for example the same epoch on both files but the same happen in
>>all files (all sites)along one month of measurements.
>>
>>Seems to be S/N from Z-extreme receivers maps to very low values in
>>(TEQC) Rinex files?.
>>Is there a way to correct this during translation?
>>Is that a problem? in TEQC or ASHTECH data?
> 
> 
> For everybody else on the list, this question is about the RINEX SNR 0-9
> flag
> on the L1 and L2 data: high values (e.g. 9 for L1, 5-7 for L2) for the Z-12
> and low values (e.g. 3 for L1, 2 for L2) for the ZXtreme in the RINEX
> fragments
> above.
> 
> The situation is that Ashtech is using the SNR slot in their binary formats
> for two different measurements of SNR depending on the receiver.  The Z-12
> outputs SNR in Ashtech's old "ireg" value, and the micro-Z and ZXtreme
> output SNR
> in dBHz.  The mapping in any official release of teqc (14 Mar 2002 or
> earlier)
> was based on the older "ireg" values only, which are numerically larger
> than
> the equivalent in dBHz.  This was resolved in the teqc development code in
> May 2003 (see http://www.unavco.org/facility/software/teqc/log.html for
> 20 May and 29 May 2003) -- but it relies on the code correctly identifying
> the receiver type first, because _there is no other reliable way_ to tell
> whether the SNRs are stored as the older "ireg" values or in dBHz.
> 
> There is also an additional piece of new code in teqc that will convert the
> "ireg" SNR to dBHz SNR if the receiver is an Ashtech Z-12 (the only case)
> if
> you are outputting S1 or S2, assuming that the code correctly identifies
> the
> receiver as a Z-12. I sent out an announcement on this topic on 22 May 2003
> to
> the old teqc email list (see
> http://www.unavco.org/facility/html_mail/teqc/msg00326.html
> -- and, BTW, no one ever responded about the HP-UX host.  hint, hint).
> 
> There is the same trouble with Trimble receivers: the older ones store SNR
> in Trimble's "AMU", and the newer ones store SNR in dBHz -- and the only
> way to tell which is which is to know what the receiver is.
> 
> This topic will continue to plague us for years.  My suggestion if you
> are using a mix of older and newer Ashtech and/or Trimble receivers is
> to minimize your dependence on the RINEX SNR 0-9 flag and instead use
> the S1 and S2 observables -- though even there you will have to know what
> the specific receiver is outputting.
> 
> BR,
> --lou
> 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Louis H. Estey, Ph.D.              office:  [+001] 303-381-7456
> UNAVCO, 6350 Nautilus Drive           FAX:  [+001] 303-381-7451
> Boulder, CO  80301-5554            e-mail:  lou  unavco.org
>     WWW:  http://www.unavco.org   http://jules.unavco.org
> 
> "If the universe is the answer, what is the question?"
>                                                 -- Leon Lederman
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
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