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Oleksandr Bezdieniezhnykh 64d961f60c [AZ-697] [AZ-702] tlog GPS truth + KHP20S30 factory calibration

Batch 98 (cycle 2) — first two PBIs of epic AZ-696 (real-flight
validation harness):

AZ-697: direct binary-tlog GPS-truth extractor

- New src/gps_denied_onboard/replay_input/tlog_ground_truth.py reads
  GLOBAL_POSITION_INT (with GPS_RAW_INT fallback) from a binary
  ArduPilot tlog via pymavlink.mavutil and returns a frozen+slotted
  TlogGroundTruth DTO with per-record ts_ns / lat_deg / lon_deg / alt_m
  / hdg_deg / vx_m_s / vy_m_s / vz_m_s.
- Promoted l2_horizontal_m + match_percentage + GroundTruthRow from
  tests/e2e/replay/_helpers.py into the new production module
  src/gps_denied_onboard/helpers/gps_compare.py. The e2e helper now
  re-exports the same objects (identity, not copies) so existing test
  imports continue working untouched.
- tests/e2e/replay/conftest.py prefers the real derkachi.tlog when
  present, falls back to the CSV synth path otherwise.
- 22 new unit tests cover AC-1..AC-5 (mypy --strict subprocess test
  included). All passing.

AZ-702: Topotek KHP20S30 factory-sheet camera calibration

- New _docs/00_problem/input_data/flight_derkachi/khp20s30_factory.json:
  fx = fy = 4644.444, cx = 960, cy = 540, HFOV ~ 23.3 deg, VFOV ~ 13.2
  deg, computed from the published 8.5 mm focal length + 1/2.8" sensor
  + 1920x1080 capture at lowest zoom step. Distortion zeroed,
  body_to_camera_se3 = identity with nadir convention. Acquisition
  method explicitly recorded as factory_sheet so downstream code can
  expect higher residual error than a lab calibration.
- _docs/00_problem/input_data/flight_derkachi/camera_info.md updated
  to document the assumptions, expected residual error window, and
  conftest pick-up rule.
- tests/e2e/replay/conftest.py::_calibration_path() prefers
  khp20s30_factory.json when present, falls back to adti26.json.
- 9 new unit tests cover AC-1..AC-4 (schema, intrinsics traceback,
  doc reference, conftest pick-up). All passing.

Test run: 45 new tests, all passing. Full-suite gate deferred to
Step 16 (after the last batch in cycle 2 per the implement skill).

Adjacent note (not fixed in this batch, recorded in the batch report):
auto_sync.py has the same redundant pymavlink type:ignore + a few
numpy/cv2 mypy --strict issues. None on this batch's path.

Refs: _docs/03_implementation/batch_98_cycle2_report.md
Refs: _docs/02_tasks/done/AZ-697_tlog_ground_truth_extractor.md
Refs: _docs/02_tasks/done/AZ-702_khp20s30_calibration.md

Co-authored-by: Cursor <cursoragent@cursor.com>

2026-05-20 16:09:03 +03:00

4.9 KiB

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Topotek KHP20S30 camera calibration (factory-sheet approximation)

Task: AZ-702_khp20s30_calibration Name: Provide a calibration JSON for the Topotek KHP20S30 nadir camera (factory-sheet approximation) Description: Compute and commit a CameraCalibrationArtifact JSON for the Derkachi camera (Topotek KHP20S30) from manufacturer factory data. Replaces the adti26.json placeholder that AC-3 currently uses. Documents the residual error vs a per-unit checkerboard refinement. Complexity: 1 point Dependencies: None Component: input_data / shared_helpers Tracker: AZ-702 Epic: AZ-696

Problem

_docs/00_problem/input_data/flight_derkachi/camera_info.md states the Topotek KHP20S30 intrinsics are unknown. tests/e2e/replay/conftest.py (line 50–56) substitutes tests/fixtures/calibration/adti26.json as a placeholder. AC-3 (≤ 100 m horizontal error for 80 % of ticks) is @xfail until a real calibration ships.

The cheapest reasonable starting point is a factory-sheet approximation — compute K from the manufacturer's published focal length + sensor geometry, accept the 1–3 % focal-length residual as a documented budget, and let AC-3 either PASS or honestly FAIL with the residual attributed.

Outcome

A calibration JSON khp20s30_factory.json exists in the Derkachi input directory, parses against the project's CameraCalibrationArtifact schema, and documents the acquisition method as factory_sheet.
camera_info.md is updated to reference the new calibration + the residual budget + the deferral handle (AZ-XXX_checkerboard_refinement).
AZ-699 (T3) uses this calibration as its --camera-calibration input.

Scope

Included

Source manufacturer factory data for the Topotek KHP20S30 (sensor: 1/2.8" CMOS, 2.13 MP, 1920×1080; lens focal length, FOV, pixel pitch).
Compute K = [[fx, 0, cx], [0, fy, cy], [0, 0, 1]] from fx = fy = focal_length_mm × (image_width_px / sensor_width_mm).
Set distortion to [0, 0, 0, 0, 0] (factory-sheet approximation).
Set body_to_camera_se3 to identity-down (nadir; camera-z = aircraft-down).
Set acquisition_method = "factory_sheet".
Write _docs/00_problem/input_data/flight_derkachi/khp20s30_factory.json.
Update _docs/00_problem/input_data/flight_derkachi/camera_info.md.
New unit test under tests/unit/calibration/ asserting the JSON parses and matches the documented inputs.

Excluded

Physical checkerboard calibration (needs hardware).
PnP-from-tlog back-computation (deferred follow-up).
Updating adti26.json or other test fixtures.

Acceptance Criteria

AC-1: Calibration JSON parses Given the new khp20s30_factory.json When loaded by the project's calibration parser (same schema as adti26.json) Then it parses without error and all fields are populated

AC-2: Doc updated Given camera_info.md before When the calibration is committed Then camera_info.md says "factory-sheet approximation; per-unit checkerboard refinement deferred — see " and lists the residual budget

AC-3: Unit test snapshot Given the new JSON When the unit test runs Then it asserts fx == fy (square pixels), cx ≈ width/2, cy ≈ height/2, distortion all zero

AC-4: T3 consumes this calibration Given AZ-699's test_derkachi_real_tlog.py When it runs Then it loads khp20s30_factory.json as --camera-calibration (no longer the adti26.json placeholder)

Non-Functional Requirements

Compatibility

JSON schema MUST be identical to existing calibration fixtures (adti26.json) — no schema changes in this task.

Unit Tests

AC Ref	What to Test	Required Outcome
AC-1	JSON loads via existing parser	Object populated
AC-3	Field values match factory inputs	fx == fy, cx/cy at centre, zero distortion

Blackbox Tests

AC Ref	Initial Data/Conditions	What to Test	Expected Behavior	NFR References
AC-4	T3 test pointed at new JSON	T3 launches without calibration parse error	Test starts cleanly	Compat

Constraints

MUST follow the calibration contract in _docs/02_document/contracts/shared_helpers/descriptor_normaliser.md (or wherever the camera-calibration schema lives).
MUST be a single committed JSON — no generator script with side effects.

Risks & Mitigation

Risk 1: Factory data unavailable at required precision

Risk: Topotek does not publish the exact focal length / sensor width to the precision needed.
Mitigation: Document the gap; ship with the best-available estimate; flag in camera_info.md so T3 surfaces the uncertainty in its failure message.

Risk 2: Residual error exceeds AC-3 budget

Risk: 1–3 % focal-length error may push horizontal error past 100 m at 1 km AGL.
Mitigation: That's the honest finding. T3 reports it. A follow-up task can pursue checkerboard refinement if needed.

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