Rotation Order; Geodetic Co-Ordinate System - Advanced Navigation Spatial OEM Reference Manual

Spatial OEM Reference Manual
Page 14 of 88
Version 2.7
Illustration 9: Second right hand rule
2.6.5

Rotation Order

When multiple axes are rotated, to imagine the final orientation the three rotations must be
performed in the order heading first, then pitch and then roll. To deduce the final orientation the unit
should first be considered level with the X axis pointing north and the Z axis pointing down.
Heading is applied first, then pitch is applied and finally roll is applied to give the final orientation.
This can be hard for some people to grasp at first and is often best learned experimentally by
rotating spatial with your hand whilst watching the orientation plot in real time on the computer.
2.7

Geodetic Co-ordinate System

The geodetic co-ordinate system is the most popular way of describing an absolute position on the
Earth. It is made up of the angles latitude and longitude combined with a height relative to the
ellipsoid. Latitude is the angle that specifies the north to south position of a point on the Earth's
surface. Longitude is the angle that specifies the east to west position of a point on the Earth's
surface. The line of zero latitude is the equator and the line of zero longitude is the prime meridian.
Illustration 10 shows how latitude and longitude angles are used to describe a position on the
surface of the Earth.