====== Navigation sensors ======
For positioning, the Otter relies upon a [[https://www.hemispheregnss.com/product/vector-v104-gps-smart-antenna/| 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.

===== Useful links =====
  * [[https://www.hemispheregnss.com/wp-content/uploads/2019/06/hemispheregnss_v104s_userguide_875-0346-000_a3.pdf|V104s User Guide]]
  * [[https://www.hemispheregnss.com/technical-documentation/|Hemisphere GNSS Technical Documentation]]