Navigation sensors
For positioning, the Otter relies upon a Hemisphere V104s. Using dual integrated GPS antennas, both GPS positioning and compass functions are achieved. It also comes with support for Space Based Augmentation Systems (SBAS) in addition to a single axis gyro and tilt sensors for x- and y-axis. This results in making a position accuracy of better than 1.0 m available 95% of the time. Communication with the v104s is done through two full-duplex RS-232. For the Otter, only one of these connections is used, RS-232-A, while RS-232-B is unused. This connection goes through a RS-232-USB adapter, to the controlling computer. There is also a PPS output for time synchronization present.
The format of the messages sent over RS-232 is NMEA 0183, with the addition of some of Hemispheres custom messages.