[FOSS-GPS] RTKPos processing options

[Felipe G. Nievinski]

>
> a) What are the differences between position modes Single,
> Static, Kinematic and DGPS/ DGNSS?
>

Basically you have two dimensions:
- with or without base station (relative or absolute positioning, AKA
baseline and point position);
- using pseudoranges only or carrier-phase too.

Then there are four combinations:
- absolute position using pseudoranges: RTKLIB's "single";
- relative position using pseudoranges: RTKLIB's "DGNSS";
- absolute position using carrier-phase & pseudoranges: RTKLIB's "PPP";
- relative position using carrier-phase and
pseudoranges: RTKLIB's "static/kinematic/moving-base".
(Confusingly, outside of RTKLIB "differential GPS" sometimes refers to
relative positioning, but I discourage that.)
"Fixed" and "PPP-fixed" are, respectively, relative and absolution
solutions where the position is not estimated as an unknown; it's useful
for atmospheric/ionospheric sensing based on observations residuals.

Both static and kinematic modes estimate a position at every observation
epoch (here RTKPLOT has no choice, as it implements a sequential filter
rather than a batch estimate), see RTKPOS Options, "Output" tab, field
"Solution for static mode" (all/final).  The effective difference is in how
much the position is allowed to vary from epoch to epoch: in kinematic
mode, some artificial position uncertainty is injected from epoch to epoch,
so as to prevent premature convergence; in contrast, in static mode,
eventually the filter will settle on a position estimate saturated with low
uncertainty, and then will stop paying attention to any new observations;
see eq.(E.7.14), p.165 in the documentation:
<http://www.rtklib.com/prog/manual_2.4.2.pdf>
Apparently there's some interplay with the "Receiver Dynamics" option, too.

See Appendix E, "Models and Algorithms", for details:
- sec. E.6, "Single Point Positioning"
- sec. E.7, "Kinematic, Static and Moving-Baseline"
- sec. E.8, "PPP (Precise Point Positioning)"


> b)  What are the differences between Integer Ambiguity Resolution options
> Continuous, Instantaneous and Fix&Hold?
>
> See Table on p.37 of the documentation:
- Continuous : Continuously static integer ambiguities are estimated and
resolved;
- Instantaneous : Integer ambiguity is estimated and resolved by
epoch‐by‐epoch basis;
- Fix and Hold : Continuously static integer ambiguities are estimated and
resolved. If the validation OK, the ambiguities are tightly constrained to
the resolved values.

T. Takasu may want to correct any misinterpretation in the above.

Best,
-Felipe.
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