fix(gps): adapt Doppler bandwidth from board validation

hardware/external/gps/rtl/pps/README.md

@@ -57,6 +57,28 @@ This keeps quality policy and the small navigation pre-filter in software
 while the deterministic PI loop, fixed-point rate state and physical edge
 generation remain in hardware.
 
+In a conventional absolute-pseudorange model, receiver clock bias and
+receiver clock drift are the level and slope of the same physical clock:
+`b_r = c*delta_t_r` and `bdot_r = c*d(delta_t_r)/dt`. The position-WLS bias
+in this project is different: subtracting the common capture time and adding
+`STARTOFFSET` makes it a reference-satellite-relative datum, approximately
+`c*STARTOFFSET - reference_range`, rather than a pure receiver oscillator
+offset.
+
+The Doppler WLS still solves a fourth, common receiver clock/frequency-drift
+state. The PPS pre-filter does not use that state directly as the derivative
+of the position-WLS datum. Instead, it predicts that datum with:
+
+```text
+position_datum_drift =
+    -reference_geometric_range_rate
+    + c * reference_satellite_clock_drift
+```
+
+The geometric term uses the Doppler-WLS receiver velocity plus the selected
+reference satellite position and velocity. The PPS RTL sees only the
+resulting timestamped reference and loop configuration.
+
 The APB register offsets live in `pps_pkg.sv`.  Multiword input fields are
 shadow registers and must be followed by one `COMMIT` write.  A new mailbox
 must not be written while `STATUS.COMMIT_BUSY` is set.

hardware/external/gps/rtl/trck_src/README.md

@@ -89,6 +89,33 @@ observation = measured_range_rate
 H = [-u_x, -u_y, -u_z, 1]
 ```
 
+Buradaki dorduncu state, tum uydu Doppler observation'larina ortak giren
+receiver clock/frequency drift'idir. Klasik mutlak-pseudorange modelinde
+receiver zaman hatasi `delta_t_r(t)` icin:
+
+```text
+clock_bias_m        = c * delta_t_r(t)
+clock_drift_mps     = c * d(delta_t_r(t))/dt
+clock_bias_m(t+dt) ~= clock_bias_m(t) + clock_drift_mps * dt
+```
+
+`clock_drift_mps`, receiver local oscillator frequency error'inin range-rate
+birimindeki ortak etkisidir. `0.1 ppm`, yaklasik `29.98 m/s`'ye karsilik
+gelir. Bu ortak state olmadan oscillator hatasi receiver hareketinin bir
+parcasi sanilirdi.
+
+Bu projedeki position WLS bias'i ise mutlak receiver clock bias'i degildir.
+Ortak capture zamani cikarildigi ve `STARTOFFSET` eklendigi icin
+referans-uyduya bagli goreli bir datum cozer. Bu nedenle Doppler WLS
+`clock_drift_mps` state'i, position WLS `clock_bias_m` degerinin turevi olarak
+dogrudan baglanmaz.
+
+Iki WLS ayri observation ve normal equation kullanir; fakat Doppler WLS tam
+bagimsiz degildir. Uydu LOS vektorlerini kurmak icin position WLS'den gelen
+guncel receiver ECEF konumunu, ephemeristen gelen uydu ECEF konum/hiz ve clock
+drift'ini kullanir. Satellite clock drift bilinen duzeltmedir; WLS'nin
+dorduncu bilinmeyeni receiver clock drift'idir.
+
 WLS en az dort gecerli uydu ister; ECEF velocity, 3x3 covariance, receiver
 clock drift ve residual RMS uretir. Fusion adapter velocity/covariance'i ENU'ya
 dondurur ve ayri velocity NIS kapisi ile 15-state ESKF'ye verir.