Vehicle navigation is implemented through openINS and various openSEA device interfaces. openINS provides a complete software implementation of an aided Inertial Navigation System (INS) suited primarily for unmanned underwater vehicles. The software package runs on Greensea's proprietary technology, openSEA, and is part of the foundation the Balefire control and navigation system is built upon.
openINS is the core computational engine, the true muscle, behind both commercially packaged and vehicle-integrated navigation systems. It offers a robust and scalable computational platform that utilizes the device library in openSEA to support more than 600 different devices, many of which are navigation sensors.
openINS provides a robust multi-state Kalman filter that fuses inertial measurements from the IMU with data from aiding sensors to create an accurate final solution of the vehicle's state.
The following table provides a summary of the contributions to the overall navigation estimate from each sensor.
| Sensor | DOF Data | Limits | Units | Orientation |
| GPS | X, Y, Z |
Surface only Low update rate |
lat,lon | TB gps |
| USBL | X, Y, Z |
Large errors Low update rate |
lat, lon | TB usbl
|
| Depth | Z | High-frequency noise | m | TB dpt
|
| Altimeter | Zref | High-frequency noise | m | TB dpt<
|
|
AHRS |
Φ, θ, Ψ
Φ, θ, Ψ |
Megnetometer-based |
rad rad/sec |
Rb AHRS
|
| IMU/Gyro | x, y, z
ϕ, ϴ, ψ |
High drift Entirely dependent on initial conditions |
Rb imu, TB imu
|
|
| DVL | x, y, z |
Requires bottom lock Requires stable platform |
m/s m/s m |
TB dvl
|
