| # Scene calibration configurations | |
| ## Files and source keys | |
| | Configuration | Source keys | Master source | | |
| | --- | --- | --- | | |
| | `WS1_2.json` | video1-video6 | video4 | | |
| | `WS3.json` | video1-video3 | video2 | | |
| | `WS4_5.json` | video1-video4 | video1 | | |
| | `WS6_7.json` | video1-video3 | video2 | | |
| Use the scene JSON and the `--source videoN` value associated with the raw CSV in `configs/source_manifest.csv`. Pixel centers and bounding-box corners must use the same image coordinate view as the control points. Source-image coordinates are mapped into the scene's master-image frame before metric conversion. | |
| ## Configuration fields | |
| | Field | Meaning and units | | |
| | --- | --- | | |
| | `template_only` | `false` for the supplied actual scene configurations | | |
| | `scene_id` | Observation-group identifier | | |
| | `master_source` | Source key defining the master-image coordinate frame | | |
| | `origin_px` | Two-element `[x,y]` origin in master-image pixels | | |
| | `rotation_rad` | Zero for the supplied road-aligned workflow | | |
| | `reference_segments` | Measured segments expressed in master-image pixels and meters | | |
| | `reference_segments[].point_a`, `point_b` | Two-element pixel endpoints in the master image | | |
| | `reference_segments[].real_distance_m` | Positive measured length in meters | | |
| | `sources.videoN.src_points` | Nx2 source-image fitting control points, in pixels | | |
| | `sources.videoN.master_points` | Matched Nx2 master-image fitting control points, in pixels | | |
| The master source has an empty source entry because its image frame is already the master frame. Non-master fitting arrays must have equal lengths, at least four point pairs and noncollinear finite coordinates. | |
| ## Transformation | |
| For each measured reference segment, calculate its real length divided by its pixel length. The metric scale is the arithmetic mean of these ratios, in meters per pixel. | |
| For a non-master source, `coordinate_transform.py` estimates the source-to-master homography from the matched fitting points using RANSAC with a 3-pixel threshold and RNG seed 0. For a master source, the source-to-master transform is the identity. After mapping a pixel point to master coordinates `(u,v)`, the output is: | |
| ```text | |
| x = (u - origin_px[0]) * scale | |
| y = (origin_px[1] - v) * scale | |
| ``` | |
| Image coordinates follow the pixel convention, with y increasing downwards. Metric x follows the aligned road axis and metric y increases upwards. Both output coordinates are in meters. Vehicle centers and all four bounding-box corners use this same transformation. | |
| ## Usage | |
| ```bash | |
| python coordinate_transform.py --input data/raw/WS3_raw_detection_data_2.csv --calibration calibrations/WS3.json --source video2 --output runs/ws3_video2_metric.csv | |
| python estimate_vehicle_length.py --input data/raw/WS3_raw_detection_data_2.csv --calibration calibrations/WS3.json --source video2 --output runs/ws3_video2_lengths.csv | |
| ``` | |
| Malformed endpoints, nonpositive reference distances, unmatched point arrays, degenerate homographies and points on a homography horizon produce explicit errors. The supplied scene JSONs provide the fitting values used by the processing commands. | |