Relocation of a seafloor transponder - Sustaining the GPS-Acoustic technique

Gagnon, KL, Chadwell CD.  2007.  Relocation of a seafloor transponder - Sustaining the GPS-Acoustic technique. Earth Planets and Space. 59:327-336.


equation, GPS-Acoustic, positioning system, seafloor geodesy, sound, speed, water


Rigid seafloor arrays of three to four precision acoustic transponders have been repeatedly positioned with the GPS-Acoustic technique to measure horizontal plate motion. In the event that one transponder becomes inactive, a replacement transponder must be precisely located relative to the existing array. Here we present a technique to determine the geodetic azimuth and baseline between the inactive and replacement transponders. We include three examples of relocations between 2002 and 2003 on the Juan de Fuca plate and near the Peru-Chile trench, which add 16-29 mm uncertainty to the GPS-Acoustic estimated position. A simulation of optimal network geometry shows that the relocation's contribution to uncertainty can be as low as 10 mm.