ROLL is measured directly on the TMU platform (see Fig.2a) and seemingly may also be deduced from the A-frame inclinometry data using a geometrical model of the antenna. To date however, the inclinometry data has not easily yielded this function. Although the tilts of the A-frames are well-measured and the location of the top of the A-frame known by geometry w.r.t. its position in the absence of tilt, the absolute vertical displacement requires knowing whether, for example, the front leg went up or the back leg went down. Current attempts in this regard have required the intermediate step of generating the track profile from the inclinometry data, and, in software, running the antenna over the profile. The problems encountered in performing this intermediate step have so far prevented a sensible prediction of ROLL from A-frame data.