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    Re: camera sextant?
    From: Marcel Tschudin
    Date: 2010 Jul 6, 15:17 +0300

    Greg's calibrations are based on calculated positions of the sun above
    the horizon. The procedure he uses for calibration would lead very
    likely to larger errors at small angles (refraction). This is a
    drawback of this calibration technique. It's for this reason that he
    didn't calibrate his lenses for small angles but only for a "useful"
    pixel/angle range. Depending on the angle to measure he selects the
    appropriate lens. It doesn't really make sense to extrapolate his
    calibration data to pixel/angle ranges which haven't been considered
    when performing the calibration. The calibration procedure adopted in
    SAMT doesn't have this drawback. With SAMT a lens can be calibrated
    for all of its pixel/angle range.
    Regarding again the conversion function: After some additional
    thoughts I gained the impression that the transformation of the second
    order polynomial calibration function into the conversion function is
    likely to result in the conversion function also to be a second order
    polynomial. I'm however not in a position to prove this

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