Slamtec devices count their angle clockwise viewed from the top (Interface Protocol spec; the official rplidar_ros node mirrors the angles for the same reason), but the decode used the raw ascending angles as CCW for a right-side-up unit and mirrored them for an upside-down one — exactly backwards. Field-verified 2026-07-23: a right-side-up C1 produced a left-right mirrored sweep against a verified right-handed reference lidar. Now: right-side-up mirrors (angle' = 2π − raw, nodes walked backwards); upside-down uses the raw ascending angles, because the physical flip already reverses the apparent rotation. The mountedUpsideDown flag finally carries its true physical meaning. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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14 KiB