Subject: Naming of biases

Dear colleagues,

It would make sense to use in the Bias-SINEX format description
adequate, unambiguous names (and acronyms) for the various type of
biases (or bias values) to be included in SINEX_BIAS files.

Note that the acronyms will also be used in the "BIAS" field for
identification of each included bias value. Example:

*-------------------------------------------------------------------------------
+BIAS/SOLUTION
*BIAS SVN_ PRN STATION__ OBS1 OBS2 BIAS_START__ BIAS_END____ UNIT __ESTIMATED_VALUE____ _STD_DEV___ __ESTIMATED_SLOPE____ _STD_DEV___
 ISB  G    G   GIEN      C1W  C2W  11:113:86385 11:115:00285 ns   0.000000000000000E+00 .000000E+00
...
-BIAS/SOLUTION
*-------------------------------------------------------------------------------

The following three kind of biases have to be distinguished:

(A)  B =     B_1
(B)  B =     B_1 -     B_2  (difference, conforming to
(B)  B = K_1*B_1 + K_2*B_2   geometry-free linear combination)
       with K_1=+1.00, K_2=-1.00 (geometry-free)
(C)  B = K_1*B_1 + K_2*B_2  (ionosphere-free linear combination)
       with K_1=+2.55, K_2=-1.55 (first-order ionosphere-free for GPS)

where B_1=B(OBS1), B_2=B(OBS2).

Variant  Type  Acronym  Name
----------------------------------------------------------------------
(1)      (A)   OCB      Observable Code Bias
(1)      (B)   DCB      Differential Code Bias
(1)      (C)   LCB      ionosphere-free LC Code Bias
----------------------------------------------------------------------
(2a)     (A)   PAB      Pseudo-Absolute Bias
(2a)     (B)   GFB      Geometry-Free Bias
(2a)     (C)   IFB      Ionosphere-Free Bias (not InterFrequency Bias)
----------------------------------------------------------------------
(2b)     (A)   B_AB     Pseudo-Absolute Bias
(2b)     (B)   B_GF     Geometry-Free Bias
(2b)     (C)   B_IF     Ionosphere-Free Bias
----------------------------------------------------------------------
(3a)     (A)   OCB      Observable-specific Code Bias
(3a)     (B)   DCB      Differential Code Bias
(3a)     (C)   ICB      Ionosphere-free (linear combination) Code Bias
----------------------------------------------------------------------
(3b)     (A)   ACB      pseudo-Absolute Code Bias
(3b)     (B)   DCB      Differential Code Bias
(3b)     (C)   ICB      Ionosphere-free (linear combination) Code Bias
----------------------------------------------------------------------
(4a)     (A)   OSB      Observable(-specific) Signal Bias
(4a)     (B)   DSB      Differential Signal Bias
(4a)     (C)   ISB      Ionosphere-free (linear combination) Signal Bias
                        (not InterSystem Bias)
----------------------------------------------------------------------
(4b)     (A)   ASB      pseudo-Absolute Signal Bias
(4b)     (B)   DSB      Differential Signal Bias
(4b)     (C)   ISB      Ionosphere-free (linear combination) Signal Bias
                        (not InterSystem Bias)
----------------------------------------------------------------------

Variant (1) is that one used in the draft format version 1.00 (Nov. 4).

Variants (2a) and (2b) were found during the bias workshop discussions.

Variants (3a) and (3b) were presented in a first message.

Variants (4a) and (4b) are more suitable (general). The term "Code" was
replaced by "Signal" (as suggested by Simon Banville from NRCan).

We would be in favor of considering variant (4a) for the Bias-SINEX
Format Version 1.00 (and document).

GENERAL REMARKS:
- An "observable" signal bias is not necessarily an observable
  quantity.
- When referring to code biases in text, one might use OCB, DCB, ICB
  (and accordingly OPB, DPB, IPB for phase biases).
- If a certain bias value should be applied to both code and phase then
  this specific bias value had to be given twice, for both the code and
  the phase observables.
- A so-called DCPB (Differential Code-Phase Bias) may be described by
  specifying a consistent pair of differing bias values for the code
  and the phase observables, or, if appropriate, by specifying a
  (sign-compatible) bias value for just one sort of observables).

Please let us know whether you have other ideas, proposals,
preferences.

Please send your feedback to biasws2015@aiub.unibe.ch.

Best regards,

Stefan


OPEN QUESTIONS:

- Extended name for ISB: Ionosphere-free and clock-coupled Signal Bias?

- BIAS MODE may be either
  o DIFFERENTIAL or
  o OBSERVABLE-SPECIFIC or PSEUDO-ABSOLUTE?

NOTES:

- Use the first character (D or I) to identify a bias (value) for
  naming in bias equations (in text): B_O (or simply B), B_D, B_I.
  Example: B_D(G,C1W,C1C)
  D: K_1=+1.00, K_2=-1.00 (geometry-free)
  I: K_1=+2.55, K_2=-1.55 (first-order ionosphere-free for GPS)