Module imu mod IOBMA

Overview

This module computes the initial camera frame orientation on the base of the GPS track and assuming the camera is oriented such that the z vector of its IMU sensor is aligned against the gravity vector. This allows to compute initial conditions for the inertial frame time integration. This procedure is typically used when the considered IMU is not able to align itself to earth.

Module nomenclature

The module waits a physical stream that contains the geopositions provided by the considered GPS reciever.

The module initiates three physical streams that contain each the three components of the three unit vectors that are used as camera frame initial conditions for time integration. The three streams contain only two elements that stores the initial conditions values twice in order to give the initial and final timestamps through the synchronization component.

Module interface

This section gives a summary of the module interface in terms of streams and devices. The order of devices and streams is given as waited by the module. The devices interface is given by :

device( Physical ) IMU sensor
device( Physical ) GPS reviever

The stream input interface is :

stream( Physical | GPS ) Geopositions

and the stream output interface is :

stream( Physical | IMU ) Frame initial x-vector
stream( Physical | IMU ) Frame initial y-vector
stream( Physical | IMU ) Frame initial z-vector

The three output streams are attached.

Module operation

Assuming the IMU provided to the module has it z axis aligned against local gravity vector, the module searches the widest motion amplitude in latitude and longitude displacement and keep the largest. It interpretes the direction of motion as the inertial frame x axis at that time. Knowing x and z axis, the y axis in computed through a cross product in order to obtain a direct frame.