I recently found some interesting articles concerning AIR Glide S and it's inertial platform in particular. Enjoy:

http://www.how2soar.de/index.php/584...ut-frustration

http://www.how2soar.de/images/H2S_me...sch%20V2.1.pdf

http://www.asl.ethz.ch/people/lestef...l/icra2012.pdf

Latter one has some heavy math in it, but worth reading anyway (incl. references for further study). They measured AIR Glide ISU accuracy with GPS signal switched off. Position error was 600 meter after 30 mins flight. Not bad.