Findclouds Manual 25
The first step of evaluation is equivalent map projection of the
fisheye image to a plain image, which shows the area of
zenith angle (The details of fisheye projection are explained in
appendix). Now each pixel of the image covers the same size
of sky area, so the cloudiness can be determined by count of
pixel.
Next step is generation of horizonmask and sunmask.
Horizonmask:
The horizonmask excludes parts of the image
from evaluation. Checkbox "Use" tells to use the mask.
Anyway a circular mask will be used, to exclude the parts
outside of the circular image.
Sunmask:
The sunmask masks an area around the sun position, which is determined by image
name (containing date and time) and longitude/latitude (Configuration of Cloudcam). The slider on
right hand side of sunmask sets the size of sunmask.
Three parts of evaluation are using the sunmask:
"Evaluation Sun Pixel"
always uses
the sunmask to restrict the sun pixel,
but does not restrict the bright pixel.
"Merge Underexposed"
can use the
sunmask for adjusting only the part around the sun by
underexposed image. It is possible to choose "Whole Blue Sky",
without using the sunmask.
"Evaluation BRBG"
For bright adjustment of BRBG evaluation the
sunmask can be applied to Bright Pixels if the checkbox "Use
Sunmask" is activated.
Information about visibility of sun:
"Sun Pixel" / "Bright Pixel"
The evaluation of "Sun Pixel"
and "Bright Pixel" is a separate evaluation to get informations
about visibility of sun. It can be activated by checkbox "Eval".
When active it produces several specific values (details in
"Sunpixel Evaluation") to determine, whether the sun is on
clear sky, partly cloud-covered or not visible.
