Changeset 10942 in ntrip for trunk/BNC/src/bnchelp.html

Timestamp:

Jun 22, 2026, 12:48:31 PM (4 months ago)

Author:

stuerze

Message:

handling of ionospheric constraints descrived/updated

File:

• trunk/BNC/src/bnchelp.html (modified) (3 diffs)

trunk/BNC/src/bnchelp.html

@@ -201 +201 @@
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 2.13.2.8 <a href=#pppseeding>Seeding</a><br>
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 2.13.2.9 <a href=#pppconstraints>Constraints</a><br>
-&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 2.13.2.9.1 <a href=#ppppseudogimobs>GIM Pseudo Observations</a><br>
+&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 2.13.2.9.0 <a href=#ppppseudogimobs>GIM Pseudo Observations - How it works</a><br>
+&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 2.13.2.9.1 <a href=#ppppseudogimobssigma>GIM Pseudo Observations Sigma</a><br>
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 2.13.2.10 <a href=#pppar>PPP-AR</a><br>
 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 2.13.2.10.0 <a href=#ppparmethod>Algorithm Description</a><br>
@@ -4501 +4502 @@
 <p><h4 id="pppconstraints">2.13.2.9 Constraints - optional</h4></p>
 <p>
-Specify, whether ionospheric constraints in form of pseudo-observations shall be added.
-Please note, this is only valid, if no ionosphere-free linear-combination is used and VTEC informations is part of the SSR stream.
-Furthermore, it would be only helpful as soon as the ionosphere information is more accurate than the code data accuracy.
-Hence, currently this option is not recommended to use!
-</p>
-
-<p><h4 id="ppppseudogimobs">2.13.2.9.2 GIM Pseudo Observations - optional</h4></p>
+Specify, whether ionospheric constraints in form of pseudo-observations shall be added to an uncombined PPP
+solution ('Pi&amp;Li', 'Pi', 'P1&amp;L1' or 'P1', see <a href=#pppobs>Section 2.13.2.1</a>). This is sometimes
+called 'PPP with pseudo-observations for STEC'.
+</p>
+<p><h4 id="ppppseudogimobs">2.13.2.9.0 GIM Pseudo Observations - How it works</h4></p>
+<p>
+When ionospheric constraints are activated, BNC derives a slant ionospheric delay (STEC) for every satellite from VTEC informations - taken
+from an Ionosphere stream/file (<a href=#pppionostream>Section 2.13.1.6</a>, <a href=#pppionofile>Section
+2.13.1.7</a>) or from the Corrections stream/file if no dedicated Ionosphere source is specified. For each GNSS
+system, one satellite is chosen as 'reference satellite' (initially the one with the highest elevation), and one
+satellite-differenced pseudo-observation per remaining satellite is added to the Kalman filter:
+</p>
+<p>
+&nbsp; &nbsp; STEC(reference satellite) &minus; STEC(satellite) = ION(reference satellite) &minus; ION(satellite)
+</p>
+<p>
+where ION(satellite) is the per-satellite ionospheric delay state already estimated by the uncombined PPP filter.
+This single difference constrains the relative ionospheric delay between satellites without removing the
+receiver's own freedom to estimate it from code and phase data. The reference satellite is kept as long as it
+stays in view; a new one is selected only once the previous reference satellite disappears from the
+observations, which avoids spurious jumps in the constraint from one epoch to the next.
+</p>
+<p>
+Pseudo-observations are treated as a soft constraint: they contribute to the solution with a weight derived from
+'Sigma GIM' (see below) but are never rejected as outliers, regardless of their residual size. They are also
+fully independent of ambiguity resolution (<a href=#pppar>Section 2.13.2.10</a>), which only ever resolves
+carrier-phase ambiguities.
+</p>
+<p>
+Please note that this option is only valid if no ionosphere-free linear combination is used and VTEC informations
+are actually available. Without VTEC data, no pseudo-observations are added and the PPP solution falls back to
+estimating per-satellite ionospheric delays from code and phase data alone. The pseudo-observations are only
+helpful once the ionosphere information is more accurate than the code data accuracy.
+</p>
+
+<p><h4 id="ppppseudogimobssigma">2.13.2.9.1 GIM Pseudo Observations Sigma - optional</h4></p>
 <p>
 Enter a 'Sigma GIM' for pseudo observations regarding the Ionosphere in meters.
 The bigger the sigma you enter, the less the contribution of GIM Pseudo observations to a PPP solutions
 based on a combination of code and phase data. '5.0' meters is likely to be an appropriate choice.
-</p>
-<p>
-Specify a maximum for residuals 'Max Res GIM' for pseudo observations regarding the Ionosphere in a PPP solution.
-'5.0' meters may be an appropriate choice for that.
-If the maximum is exceeded, contributions from the corresponding observation will be ignored in the PPP solution.
 </p>
 <p><h4 id="pppar">2.13.2.10 PPP-AR - optional</h4></p>
@@ -6742 +6767 @@
    PPP/constraints  {Specify, whether ionospheric constraints in form of pseudo-observations shall be added [character string: no|Ionosphere: pseudo-obs]}
    PPP/sigmaGIM     {Sigma for GIM pseudo observations in meters [floating-point number]}
-   PPP/maxResGIM    {Maximal residuum for GIM pseudo observations in meters [floating-point number]}
    PPP/arGPS        {Ambiguities for GPS should be resolved: [integer number: 0=no,2=yes]}
    PPP/arGalileo    {Ambiguities for Galileo should be resolved: [integer number: 0=no,2=yes]}