Changes between Version 3 and Version 4 of Sensors/RCD_CH39


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Timestamp:
Feb 15, 2012, 1:10:08 PM (13 years ago)
Author:
mark1
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  • Sensors/RCD_CH39

    v3 v4  
    1 == Leica RCD digital camera ==
     1= Leica RCD105 digital camera =
    22
    3 The system has a 39 megapixel digital camera, referred to as the "RCD" or "CH39", with the following characteristics:
    4  * 7216x5412 resolution, 12 bit [=~57MB raw]
    5  * 60mm lenses (changeable), with 44.2 degree x 34.0 degree FOV
    6    * fixed aperture (f-4.0)
    7  * pixel size 6.8microns (= ~15cm ground resolution at 1350m)
    8  * up to 1/4000 exposure time
    9  * Max frame rate 0.5Hz (2.02s per frame)
    10  * serial number 21
    11  * shutter is a dual curtain, one opening to start the exposure and the other closing to finish it
    12    * exposure will therefore occur at different times along the focal plane
    13    * 8ms for shutter to open and close, so there's a 4ms time difference between the top and bottom of the CCD acquiring light
    14  * lens distortion is a maximum of 2% at the edges of the FOV
    15    * distortion measurements are available
    16  * CCD is a Bayer array (raw 7162 x 5389), with a pixel layout as below.  In the final processed TIFF, these pixels are blended and interpolated to make a full RGB grid.
    17 || Blue  || Green ||
    18 || Green || Red ||
     3The RCD105 is a medium-format digital camera which is integrated together with the Leica ALS-50 Lidar system.
    194
    20 Logfiles contain various handy info, notably the image event file contains GPS time, (real time) pos/att and picture id
    215
    22 Calibration files are required and supplied by Leica (dark, gain and camera parameters).
     6== Raw data format ==
    237
    24 File name convention is: `DDHHMMSSXXXXXXGN.raw`
     8The RCD105 data are captured in compressed 12-bit .raw files of approximately 57MB size. To accompany the .raw files, various ASCII header files are generated. The most useful of these is the image events file which contains time stamp information for each photograph, including real-time aircraft position and attitude data.
     9
     10The raw file name convention is: `DDHHMMSSXXXXXXGN.raw`
    2511 * DD = day of month
    2612 * HHMMSS = timestamp
    … …  
    2814 * G = gain (1-4)
    2915
     16== Calibrations ==
    3017
    31 === Basic Image Processing ===
     18The RCD system is calibrated at Leica every 2 years. The latest calibration certificates are included here:
    3219
    33 The RCD outputs raw images which are processed to create TIFFs. There are several image processing steps that are applied to each raw image.
     20 * [raw-attachment: February 2010]
     21 * [raw-attachment: July 2008]
    3422
    35  * Bias Correction [[BR]] The XXXd.tif file is used to subtract for ‘dark’ signals. “XXX” is the name of the camera parameters file.
    36  * System Response Correction [[BR]] The XXXg.tif file is used to correct for Pixel Response Non-Uniformity (PRNU) and for a first order system falloff in light across the image frame. “XXX” is the name of the camera parameter file.
    37  * Color Processing [[BR]] The XXXp.txt camera parameter file contains information on the camera regarding the Bayer array, color response, white balancing, and flaws. It is used to correctly interpolate from a Bayer image to full color RGB TIFF image,  correct for color, white balance, and interpolate over flaws.
     23The raw calibration files include dark values, gains and camera parameters.
     24
     25== Specifications ==
     26
     27|| Detector size ||  39 Mega-pixels @ 7216x5412 resolution ||
     28|| pixel size || 6.8 microns giving ~15cm resolution at 1350m flying height ||
     29|| lenses || 60mm (changeable) with 44.2 degree x 34.0 degree FOV ||
     30|| aperture || fixed f-4.0 ||
     31|| exposure time || up to 1/4000 ||
     32|| Maximum frame rate || 0.5 Hz ||
    3833
    3934
     35The shutter is a dual curtain, one opening to start the exposure and the other closing to finish it.
     36 * exposure will therefore occur at different times along the focal plane
     37 * 8ms for shutter to open and close, so there's a 4ms time difference between the top and bottom of the CCD acquiring light
    4038
    41 === Orthophotos ===
     39Lens distortion is a maximum of 2% at the edges of the field of view.
     40 * distortion measurements are available
    4241
    43 This apparently takes another week long training course.  We do have the basic software to do it but limited knowledge.  Basic process is to determine the camera parameters, correct and overlay the images, keeping ideally only the most central parts.  You then have to manually check through, especially along seams, and manually move the seam line in some instances (e.g. when perspective effects result in odd errors due to the seam hitting a tall building).
     42The CCD is a Bayer array (raw 7162 x 5389), with a pixel layout as below.  In the final processed TIFF, these pixels are blended and interpolated to make a full RGB grid.
     43|| Blue  || Green ||
     44|| Green || Red ||
     45