[IGSSTATION-4215] Re: [IGS-ACS-485] Possible 0.25 cycle offset in TPS NETG3 measurements

Mon Jan 31 00:53:25 PST 2011

Brian,

Thank you for your message, and the clarifications on teqc parameters.
It is interesting to have the C2 observable for new studies, so I hope 
you will find a solution to have consistent data for the different users.

Best regards,

Flavien

Donahue, Brian a écrit :
> Flavien, 
>
> Many thanks for pointing out this problem with NRCan topcon files (see below).  As Flavien pointed out we upgraded to teqc version 2010Oct21 on day 296 of 2010.  In this version of teqc the default way in which L2 data from C2 capable receivers was changed.
>
> Here is a snippet that Lou passed along from the release notes:
> ----------
> 2009 Aug 3: current plan for implementing L2 from L2C:
>
>      * using +C2 or -O.obs with C2: +L2C_L2 and -L2C_L2 are ignored;
>       the L2 (and S2, D2) are based on L2(L2C) if present, based on
>       L2(P2) otherwise
>      * using -C2 and -O.obs w/o C2: +L2C_L2 or -L2C_L2 takes effect,
>        allowing pure L2(L2C) or pure L2(P2), respectively; default would
>        continue to be -L2C_L2, i.e. RINEX L2 (and S2, D2) based on L2(P2)
>
> implemented for reading Leica MDB record 0x77 (119)
> ---------- 
>
> So to summarize:
> prior to day 296/2010 we were generating rinex files that reported:
> Non Block IIR-M's L1P,L2P,P1,P2,C1  
> Block IIR-M's L1P,L2P,P1,P2,C1,C2
>
> After 296/2010 our files contained 
> Non Block IIR-M's L1P,L2P,P1,P2,C1
> Block IIR-M's L1P,(L2C),P1,P2,C1,C2
>
> Lou also mentioned (and I'll summarize):
> ----------
> In our Topcon (and some other) receivers the 90º phase shift between
> L2C and L2P transmitted phases has not been removed.  
> Teqc gives the phases as reported in the raw data.  
> You can distinguish between RINEX L2 from L2C vs. from L2P by the antispoofing flag value:
> an L2 from L2P will have the antispoofing bit 2 set, i.e.:
>
>   125883546.170 7  98091067.49144  23954840.465
>                                ^
>                              note!
>
> whereas an L2 from L2C will not have the antispoofing bit 2 set, i.e.:
>
>   112613189.324 8  87750536.440 8  21429576.155    21429573.930
>                                ^
>                              note!
>
> So the processing software has to deal with the 90º phase shifts
> with this type of RINEX.
> ----------
>
> Having said that, it wasn't our intention to force the processing software to check for the antispoofing bit and I will go ahead and revert back to our old way of handling the topcon data where we always report L2P phases.
>
> I will also try to recreate as much older rinex files as I can.  We have about 1 month of raw files available online.  I will follow up with another IGS station message at that time.
>
> Sorry for any inconvenience this has caused and a big thanks to Lou Estey for clarifying things.
>
> Regards,
> Brian
>
>
> Brian Donahue 
> bdonahue at NRCan.gc.ca, 613-947-4246, facsimile / télécopieur 613-995-3215 
> Geodetic Survey Division 
> Natural Resources Canada, 615 Booth Street, Ottawa, Ontario K1A 0E9 
> Ressources naturelles Canada, 615 rue Booth, Ottawa, Ontario K1A 0E9 
> Government of Canada / Gouvernement du Canada 
>
>
> -----Original Message-----
> From: igs-acs-bounces at igscb.jpl.nasa.gov [mailto:igs-acs-bounces at igscb.jpl.nasa.gov] On Behalf Of Flavien Mercier
> Sent: January 28, 2011 04:24
> To: jim.ray at noaa.gov; igs-acs at igscb.jpl.nasa.gov
> Cc: Loyer Sylvain; felix perosanz
> Subject: [IGS-ACS-485] Possible 0.25 cycle offset in TPS NETG3 measurements
>
> Dear all
>
>
> When investigating anomalies in our widelane processing, I observed that 
> the TPS NETG3 receiver on WHIT has systematic 0.25 cycles offsets in the 
> zero difference widelane ambiguity on day 300 year 2010 on some 
> satellites. These satellites are the IIRM (PRN 5,7,12,15,17,29,31).
> After investigation, it appears that this is also the case on other TPS 
> NETG3 receivers.
>
> So I checked this systematically on a longer duration :
>
> - days 250-331, receiver WHIT : the change in the L2 observables occurs 
> after19 h for day 295. I noticed in the header that the version of teqc 
> changed day 296 :
>
> -------- whit2940.10d.Z -------------
> teqc  2009Mar23                         20101021 01:05:03UTCPGM / RUN BY 
> / DATE
> 01545               TPS NETG3           3.4                 REC # / TYPE 
> / VERS
> -------- whit2950.10d.Z -------------
> teqc  2009Mar23                         20101022 01:05:03UTCPGM / RUN BY 
> / DATE
> 01545               TPS NETG3           3.4                 REC # / TYPE 
> / VERS
> -------- whit2960.10d.Z -------------
> teqc  2010Oct21                         20101023 01:05:02UTCPGM / RUN BY 
> / DATE
> 01545               TPS NETG3           3.4                 REC # / TYPE 
> / VERS
> -------- whit2970.10d.Z -------------
> teqc  2010Oct21                         20101024 01:05:03UTCPGM / RUN BY 
> / DATE
> 01545               TPS NETG3           3.4                 REC # / TYPE 
> / VERS
>
>
> - day 252, receivers BAKE, DUBO,SCH2, VALD and WHIT : no offset at all, 
> the teqc version are 2009Mar23 for these files.
>
> - day 300, receivers BAKE, DUBO,SCH2, VALD and WHIT : offsets are 
> present on all receivers, these offsets are removed by subtracting 0.25 
> cycles on the L2 measurements corresponding to the passes where C2 is 
> also measured (the IIRM satellites). The teqc versions are 2010Oct21.
>
> I am not familiar with the teqc use for these receivers, perhaps it is 
> not the origin of the offsets. Also we have to confirm that these 
> offsets are really on L2 (which is likely the case if L2 is related to 
> the C2 observable now), or if they are on other observables (the 
> widelane combination we process uses the P1,P2,L1,L2 data as named in 
> the rinex header).
>
> Best regards
>
> Flavien Mercier
>
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