Gillian Sharer staff Oct. 10, 2013, 10:43 a.m.
The orientation of USArray Transportable Array (TA) instruments is measured when the sensor is first placed at the site using an IXSEA OCTANS (fiber optic gyroscope technology). The OCTANS has an accuracy on the order of 0.1 degrees. There may be additional errors introduced with the actual placement of the sensor that are not well known. When the station is removed, the orientation is measured again with the OCTANS and the metadata is updated as necessary.