| | 1 | == Leica RCD digital camera == |
| | 2 | |
| | 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 | * 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 || |
| | 19 | |
| | 20 | Logfiles contain various handy info, notably the image event file contains GPS time, (real time) pos/att and picture id |
| | 21 | |
| | 22 | Calibration files are required and supplied by Leica (dark, gain and camera parameters). |
| | 23 | |
| | 24 | File name convention is: `DDHHMMSSXXXXXXGN.raw` |
| | 25 | * DD = day of month |
| | 26 | * HHMMSS = timestamp |
| | 27 | * XXXXXX = incrementing picture id |
| | 28 | * G = gain (1-4) |
| | 29 | |
| | 30 | === Orthophotos === |
| | 31 | |
| | 32 | 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). |