Changes between Version 1 and Version 2 of Sensors/Hawk


Ignore:
Timestamp:
Feb 14, 2012 12:10:03 PM (8 years ago)
Author:
mark1
Comment:

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  • Sensors/Hawk

    v1 v2  
    1010
    1111The .nav files are a collection of different 'messages'. These contain the real-time position and attitude of the aircraft as well as periodic time stamps marking the start of the flight line capture.
     12
     13=== Timing ===
     14
     15The Eagle instrument is connected to a nav-sync box that timestamps the start of acquisition against GPS time.  This measures the time to the next GPS pulse-per-second, from the first start of integration pulse from the camera that occurs after the start of acquisition pulse from the recording system.
     16
     17The frame grabber lag time is unknown.  Previously it was thought to be 55ms regardless of frame rate (i.e. a frame is captured 55ms before the nav sync pulse), but this was actually a once-off correction applied by Specim for a single dataset.  What was called the frame grabber lag time is actually an unknown timing error in the system.  Further work is underway to isolate this.
     18
     19Consequently the timing of a start of acquisition is `next_GPS_PPS - navsync_time - <unknown and variable error>ms`.
    1220
    1321== Specifications ==