Data Processing

Abstract

The methods developed in this book are used to calculate high rate position and orientation states of a moving body relative to the earth using a comprehensive sensor suite. Unfortunately, the different sensors move relative to each other and measure quantities along different, uncoupled axes. For example, the MotionPack’s accelerometers measure acceleration and its rate gyros measure angular velocity along three perpendicular directions that move with the ship with the acceleration signals contaminated by gravitational acceleration, which is always orientated towards the center of the earth. Similarly, the TCM2 compass measures the heading of the moving body with respect to the magnetic North, and the tilt sensor measures the roll and pitch angles with respect to the ship. Conversely, the GPS computes geodetic latitude, longitude and height above sea level relative to the rotating earth. Therefore, the data measured from each one of the sensors need to be rotated into a common frame of reference. The first section of this chapter, section 3.1.1, defines the different reference frames used. The second section, section 3.2, derives the transformations necessary to convert vectors between the reference frames and into a common reference frame. The third section, section 3.3, describes the data fusion algorithm and its implementation. Finally, the last section, section 3.4, defines the method used to process the ADCP data.