Changes between Version 35 and Version 36 of Processing/LeverArmOffset


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Timestamp:
Aug 10, 2012 3:23:12 PM (7 years ago)
Author:
knpa
Comment:

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  • Processing/LeverArmOffset

    v35 v36  
    11== Lever arm offset details ==
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    3 This page gives details of how the lever arm offset is calculated.
    4 
    5 All nav is transformed back to the master antenna on the rear of the cabin roof, and then [wiki:Processing/Flow/aznav aznav] transforms nav from there to each sensor as required when the individual sensor data is processed. AT4 nav is already wrt this antenna, and the IMU data is transformed back to the antenna during Applanix processing.
    6 
    7 The distance is from the phase centre of the master (rear) antenna to each sensor's "prime" point; so for the ATM it is the scan mirror centre, for the Eagle, Hawk and CASI ideally the focus point of the lens.
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    9 The angles (as used in aznav) are:  gamma is the positive angle from the vertical through the antenna to the sensor prime point and delta is positive to starboard from the centre line direction of the aircraft.
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    11 Initially it is necessary to make sure you have the correct sensor prime point coords as observed.
    12 
    13 Then aznav sorts out what axis system has been used by the surveyors and swaps the coordinates around until it gets it in the NASA Standard Aircraft system  [ Y+ port, X+ tail to nose, Z+ up ]. Then do the angle calcs.
     3This page gives details of the lever arms used when processing data collected from the sensors.
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     5Surveys are undertaken by an external company, usually once a year.
     6
     7Where possible, the lever arms use precise prime points, e.g. the phase centre of the master (rear) antenna, the centre of the IMU, the scan mirror centre for the LiDAR and the focus point of the lens for the Eagle, Hawk and CASI.
     8
     9Since 2011, nav data is transformed from the IMU/GPS to an imaginary reference point below the plane (the PAV80). The relevant sensor processing software will then transform from this point to the correct sensor.
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