test(e2e): add SyntheticAdapter for harness self-tests

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/gps_denied/testing/datasets/synthetic.py

@@ -0,0 +1,93 @@
+"""Synthetic dataset — straight-line eastward flight at constant altitude.
+
+Used for harness self-tests. No image files; image_path is empty so the harness
+can substitute a generated checkerboard so existing OpenCV readers can open them.
+"""
+
+from __future__ import annotations
+
+from typing import Iterator
+
+import numpy as np
+
+from gps_denied.testing.datasets.base import (
+    DatasetAdapter,
+    DatasetCapabilities,
+    DatasetFrame,
+    DatasetIMU,
+    DatasetPose,
+    PlatformClass,
+)
+
+GRAVITY = 9.81
+EARTH_R = 6_378_137.0  # WGS84 semi-major axis, metres
+
+
+class SyntheticAdapter(DatasetAdapter):
+    """Deterministic straight-line eastward flight for harness smoke-tests."""
+
+    def __init__(
+        self,
+        num_frames: int = 100,
+        fps: float = 5.0,
+        imu_rate_hz: float = 100.0,
+        speed_m_s: float = 10.0,
+        altitude_m: float = 100.0,
+        origin_lat: float = 49.0,
+        origin_lon: float = 32.0,
+    ) -> None:
+        self._num_frames = num_frames
+        self._fps = fps
+        self._imu_rate_hz = imu_rate_hz
+        self._speed = speed_m_s
+        self._altitude = altitude_m
+        self._origin_lat = origin_lat
+        self._origin_lon = origin_lon
+
+    @property
+    def name(self) -> str:
+        return "synthetic"
+
+    @property
+    def capabilities(self) -> DatasetCapabilities:
+        return DatasetCapabilities(
+            has_raw_imu=True,
+            has_rtk_gt=True,
+            has_loop_closures=False,
+            platform_class=PlatformClass.SYNTHETIC,
+        )
+
+    def iter_frames(self) -> Iterator[DatasetFrame]:
+        period_ns = int(1e9 / self._fps)
+        for i in range(self._num_frames):
+            yield DatasetFrame(
+                frame_idx=i,
+                timestamp_ns=i * period_ns,
+                image_path="",  # harness fills from generator
+            )
+
+    def iter_imu(self) -> Iterator[DatasetIMU]:
+        duration_s = self._num_frames / self._fps
+        n_samples = int(duration_s * self._imu_rate_hz)
+        period_ns = int(1e9 / self._imu_rate_hz)
+        for i in range(n_samples):
+            yield DatasetIMU(
+                timestamp_ns=i * period_ns,
+                accel=(0.0, 0.0, -GRAVITY),  # gravity only; constant velocity
+                gyro=(0.0, 0.0, 0.0),
+            )
+
+    def iter_ground_truth(self) -> Iterator[DatasetPose]:
+        period_ns = int(1e9 / self._fps)
+        for i in range(self._num_frames):
+            t_s = i / self._fps
+            east_m = self._speed * t_s
+            # Local tangent plane approximation (small distance)
+            dlon = np.degrees(east_m / (EARTH_R * np.cos(np.radians(self._origin_lat))))
+            yield DatasetPose(
+                timestamp_ns=i * period_ns,
+                lat=self._origin_lat,
+                lon=self._origin_lon + dlon,
+                alt=self._altitude,
+                qx=0.0, qy=0.0, qz=0.0, qw=1.0,
+            )