1. Allan , J. 1992 More GPS developments Pilot 60 61
2. A video tracking system for a light aircraft;Ekin;Photogrammetric Record,1988
3. The resurvey of the six-inch maps of Scotland;Halliday;Ibid.,1960
4. Computer controlled survey flight based on a low cost GPS C/A code receiver;Heimes;Ibid.,1992