The spatially calibrated coordinates of line mean position is returned as a length-2 array, X followed by Y. The Value for N lines is exposed as a 2-dimensional array of 2 by N.
For a polyline (mLnSegmentCount greater than 1), the mean position will usually not fall on the polyline.
The mean position coordinate is computed as the mean of the coordinates of the center of each line segment, weighted by segment length.