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3DM-GX4
™
-45
™
Inertial Navigation System
User Manual
Sensor Measurements
31
4.4.2
North East Down (NED) Frame
The North, East, Down (NED) frame is a local coordinate frame which is formed by a
tangent plane located at a particular point (current coordinates) on the WGS84 reference
ellipse. The NED frame is constructed with the (true) North vector along the line of
longitude, the East vector along the line of latitude, and the Down vector normal to and
towards the tangent plane (
Figure 20 - North East Down Frame
). The assumption when
using the NED frame is that the local surface can be reasonably approximated by a flat
plane. For most applications, this assumption is valid and provides a more intuitive reference
frame for expressing velocity and attitude information than a global frame.
The 3DM-GX4-45
™
reports velocity in this frame and attitude with respect to this frame.
Figure 20 -
North East Down Frame