Measurement of displacement of a beam due to motor step on the backscattermeter at LAPP

These gwf files can be read with lalsuite or Fr. Each file contains "V1:Camera_Scatter_FitPosY" and "V1:Camera_Scatter_FitPosX" channels, corresponding to the center of a gaussian fit in X and in Y respectively (camera axis are inverted). This can be used in conjunction with a public code. Each filename is formatted as follows: snail_N{number of point between the border and the center}_S{reference axis}{reference direction}{number of steps for this reference}[_old]_{id}-{GPS time}-{duration in second}.gwf Where "reference axis" can be "X" or "Y" and "reference direction" can be "p" (positive) or "n" (negative). These reference metadata is used to get the number of steps associated to each direction and axis using tables. The number of step done by the motor in one direction is given by the formula $\lfloor { { \frac { {f}_{a} } { {f}_{r} } } \cdot { n_{r} } } \rceil$ where $f_a$ is the factor associated to the wanted tuple (axis, direction), $f_r$ is the factor associated to the reference tuple (axis, direction) and $n_r$ the number of step done in the reference direction. If the [_old] part is present, the table to use is: name direction axis factor i + X 1.00 (ref) j - X 0.90 k + Y 1.95 l - Y 1.19 if the [_old] part is NOT present, the table to use is: name direction axis factor i + X 1.00 (ref) j - X 0.90 k + Y 1.95 l - Y 1.40 For Syp100, this will give $\lfloor {\frac{ 1 } {1.95} \cdot { 100} } \rceil = 51$ steps in X+, $\lfloor {\frac{0.90}{1.95} \cdot {100} } \rceil = 46$ steps in X-, 100 steps in Y+ and $\lfloor { { \frac { 1.40 } { 1.95 } } \cdot { 100 } } \rceil = 72$ steps in Y-.