Changes between Version 8 and Version 9 of Sensors/LeicaLIDAR/FWMikesNotes


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Timestamp:
Feb 8, 2010 2:29:01 PM (10 years ago)
Author:
mggr
Comment:

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  • Sensors/LeicaLIDAR/FWMikesNotes

    v8 v9  
    2222Processing note: the trigger from the discrete system appears to have a small delay (order of 7ns?), that is different for the two possible laser pulse rates and also may be dependent on temperature (unproven).  This delay manifests as an offset between the discrete returns and the matching waveform peaks.  At the time of writing, it is corrected by a manual / statistical approach (see below).
    2323
    24 Some other important points:
    25  - normal lidar returns based on threshold, then look for peaks
    26   - requires a non-peak gap after a peak is found, so double peaks not spottable without  fwd
    2724
    2825FWD filestructure:
     
    3835   
    3936
    40 
    41 things one can detect.. maybe..
    42  - pulse stretching (return pulse longer than laser pulse
    43   - slopes
    44   - low vegetation (ie. may need to adjust "ground" peak downwards a little)
    45  - indication of biomass by evaluating area under peak
    46  - better vertical resolution/distinction of objects
    47 
    48 angle of laser may make a difference  (flat ground at nadir is a slope at edge of fov, or cutting through vegetation)
     37== Benefits of full waveform ==
     38
     39Things one can detect.. maybe..:
     40 * pulse stretching (return pulse longer than laser pulse), indicating:
     41   * slopes (angle of slope means a longer return than a flat bounce)
     42   * detection of low vegetation (i.e. the discrete return may need to adjust "ground" peak downwards a little)
     43   * note the angle of the laser makes a difference (flat ground at nadir is a slope at edge of fov, or cutting through vegetation)
     44 * indication of biomass by evaluating area under peak curve
     45 * better vertical distinction of objects
     46   * discrete returns are based on the intensity exceeding a threshold then finding a peak ; after this peak there is a fairly long period where no secondary peaks can be detected
     47   * FWD allows you to implement your own peak finding algorithm that can distinguish these
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