Compares COLMAP camera centers (images.txt) with three imagej-elphel position
columns (ERS x/y/z, IMS imsX/Y/Z, PIMU pimuX-C/Y-C/Z-C) using 7-DOF Sim(3)
alignment (Umeyama 1991).  Reports scale, rotation (Euler angles), per-frame
residuals in both COLMAP units and physical meters, and saves a CSV.

Key results for water-tower scene (1763233718_057205, rect/PINHOLE, 378 frames):
  Scale ~0.054 (1 COLMAP unit ≈ 18.5 m; flight spans 225 m → 12.2 COLMAP units)
  ERS RMSE=8.3 m, max=19.6 m at trajectory endpoints
  Worst frames are at both ends of the 378-frame sequence — consistent with the
  SfM nadir doming artifact (camera orientations rotate outward from center)
  Two near-zero crossings at frames ~74 and ~296 confirm dome vs straight-line fit
Co-authored-by: Claude <claude@elphel.com>