Applanix POS MV V5, Инструкция по установке и эксплуатации

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POS MV V5 Installation and Operation Guide
Theory
of Operation
Copyright © Applanix Corporation, 2017
B-2
direction and time of travel from a known starting point. The errors inherent in this form of navigation arise
from two sources:
• Uncertainty in determining the position of the starting point. This contributes a fixed error in the
dead reckoning position. The magnitude of this error is the same as the error in determining the
position of the starting point.
• Inevitable inaccuracies in the measurement of speed and heading. Errors in the dead reckoning
position will increase with time as the effects of these inaccuracies accumulate.
Dead reckoning requires no external support from radio navigation aids. It can be reasonably accurate if
the system compensates for errors in the measurement of speed and heading, and for the effects of wind,
tide and current.
To implement dead reckoning an INS contains sensitive components that include:
• Accelerometers to sense the specific forces of gravity, plus the forces that accelerate the INS with
respect to the Earth.
• Gyros to sense all angular rates of rotation experienced by the INS with respect to an inertial
frame of reference.
Fro m the inertial measurements delivered by these components the INS solves Newton’s equations of
angular and translational motion on the approximately spherical surface of the Earth, and computes a full
range of motion parameters:
• The orientation of the IMU (roll and pitch) with respect to a locally level reference plane.
• The heading of the IMU with respect to geographical north.
• The latitude, longitude and altitude of the IMU on the surface of the Earth.
In addition to these, appropriate calculations will also deliver measurements of velocity and track over the
ground.
How INS Navigates
The accelerometers and gyros sense specific forces and angular rates relative to an inertial frame of
reference. An inertial frame of reference is one that experiences no accelerations or angular rates of its
own. Therefore, in such a reference frame, Newton’s laws of motion apply without requiring corrections
for accelerations or rotations of the frame.
Navigation on the Earth introduces forces and angular rates due to gravity and the rotation of the Earth.
The accelerometers and gyros will sense these forces and movements, even when the INS is stationary
relative to the Earth: Any object on the surface of the Earth experiences the force due to gravity. It also