Changes between Version 10 and Version 11 of Sensors/LeicaLIDAR/MikesNotes


Ignore:
Timestamp:
Aug 26, 2008 6:39:40 PM (11 years ago)
Author:
mggr
Comment:

--

Legend:

Unmodified
Added
Removed
Modified
  • Sensors/LeicaLIDAR/MikesNotes

    v10 v11  
    2828
    2929Most Leica systems are mounted "laser backwards" (cables will be at the rear if this is so) - ensure that z=180 in the IPAS Pro aircraft tab.
     30
     31=== Other error sources ===
     32
     33Atmospheric effects; the light path may bend due to atmospheric refraction, density effects, etc causing the laser to hit the ground earlier or later than expected, or in a different position.  This will be most noticeable at the edges of the swath where there are longer path lengths (and more atmosphere to pass through) and may look like the swath curls up or down at the edges (path length error), or may look like compression or stretching of the edges (if there is horizontal divergence).  The error was claimed to be a fraction of a meter at 6km altitude (i.e. not well bounded).  Measurement of temperature may help with this effect, but was said to be a minor value.
     34
     35Range correction error; if the range correction is wrong, the electronics will measure the path length incorrectly.  Points at nadir will be in error vertically only and points at the edge will have a vertical and horizontal error.  The error will make a flat piece of land look like a smile (one can only get "late" measurements?).
     36
    3037
    3138== Mission planning considerations ==
     
    7077 * ... pulse frequency, scan angle, etc [TBD]
    7178
    72 Required measurements for processing:
    73  * GPS and IMU data (including a basestation if not using PPP)
    74  * Pressure and temperature measurements at the plane position above the site [this affects how long it takes the laser light to move through the air]
    75 
    7679== Recommendations ==
    7780
     
    8184
    8285Items required from every flight:
    83  * GPS/IMU data
     86 * GPS and IMU data (including a basestation if not using PPP)
    8487 * Raw laser data
    8588 * Logfiles from LIDAR
    8689   * Flight logfiles are useful too, if the LIDAR flight planning software is used
    8790 * RCD & webcam images
     91 * Pressure and temperature measurements at the plane position above the site [this affects how long it takes the laser light to move through the air]
    8892
    8993Items required in general:
     
    148152
    149153Encoder Offset (scan angle correction).
    150  * The rotating mirror has
     154 * The rotating mirror has a (optical?) shaft encoder attached that tells it the position of the mirror.  The mirror will not be mounted exactly at nadir relative to the shaft encode and this value measures the offset between the centre of the scan pattern and the centre point of the encoder.  The value is measured in "ticks" and will appear quite high as the shaft encoder has a high resolution (order of millions of ticks).
     155 * Measured in factory and provided by Leica.
    151156
    152157== Calibration site requirements ==