Add object calibration

README.md

@@ -21,7 +21,8 @@ simply skips to the freshest frame:
    configures the radar, performs the frequency sweep, and publishes raw S11/S21
    traces.
 2. **Preprocessing** — `data_preprocessor` applies through/OSL calibration,
-   reference subtraction, and optional frequency-domain notch filtering.
+   reference subtraction, optional frequency-domain notch filtering, and an
+   optional object-based MIMO correction of S21.
 3. **Processing** — `data_processor` runs the selected processing mode and emits
    results (pass-through traces, B-scan images, GPR images with detected objects,
    or 3D SAR views). Detected objects are additionally broadcast to subscribers
@@ -223,13 +224,29 @@ result count or Stop; Stop and closing the window flush accepted data. Acquisiti
 rings use latest-wins delivery, so disk recording cannot recover sweeps overwritten
 before the GUI receives them. NumPy datasets preserve both S-parameters, capture
 windows, every supported result payload, and processing time. Failed exports remove
-their staging files, leaving existing datasets intact.
+their staging files, leaving existing datasets intact. Companion profiles retain
+the radar, antenna layout and preprocessing used for acquisition, including when
+another profile is loaded after Stop.
 
 Calibration and reference sets keep their trace arrays and metadata together in one
 atomically replaced NPZ archive, with a readable JSON sidecar. Earlier NPZ/JSON pairs
 remain supported. Invalid trace shapes, duplicate combinations and non-finite
 calibration/reference values are rejected before a saved set is replaced.
 Median captures also require identical frequency axes and channel coverage.
+In **Preprocessing Panel**, create or select the ordinary S21 calibration and
+empty-scene reference first. **Create…** in the **Object Calibration** row opens a separate step:
+take fresh sweeps, then enter the measured reflector centre X/Y/Z in metres.
+Height above ground, radar pitch and sphere radius follow `mimo_calibration.py`;
+several reflector positions may contribute to one calibration. The calculation
+shows each pair's phase at the target before/after correction and its coherence.
+The selected reference is already subtracted, and the previous object correction
+is disabled while these sweeps are acquired. Saved object corrections apply on the
+next **Start**, after notch filtering and before any processor; **Off** disables
+them. Changing antenna geometry disables an incompatible correction and reloads
+acquisition without restarting the application. **Import…** in that row
+accepts the example's `cal_*.npy` / `cal_meta.json` format; the example and GUI share
+one numerical implementation.
+
 Dataset replay restores both recorded S-parameters and orders long recordings by
 their numeric index; older S21-only datasets still replay with zero S11. Offline
 JSON conversion and the GUI share the same sweep-matching code.