Development of Automatic Composite Processing System for NOAA/AVHRR GAC data
Cloud screening
This cloud detection scheme is to apply to one way procedure to detect t cloud. In this study, the purpose of making this procedure is to apply to selection of GCPs . therefore, this procedure is applied during the day time and sing channel 1 thresholding. in the channel 1 is corrected by cos q . q is the appropriate solar zenith angle.
Automatic selection of GCPs
At the path mapping, it is necessary to secret GCP point by path . but we success to make this process automatically by using the GCP ID number plotted image and the swath region image. they are given as follows. ( Figure 2).
Figure 2: Automatic selection of GCPs.
1) GCP ID number ploted image
GCP each have ID number. And the number was made by ploting ID number on the image. This image size is
same of latitude/longitude grid system.
2) Swath region image.
this image was made of latitude/longitude at the start and end of swath . they are included in the line header of GAC raw data. For such information. It is possible to make a swath reign image .
the method to select GCPs is shown in figure 2. the purpose of this way is to make a GCP ID number list which is used automatic GCP matching procedure. Therefore, you should compare GCP ID number plated image and swath region image. the comparing is done pixcel by pixcel, if a pixcel count on the swath region is true and a pixcel on the GCPL ploted image has count of ID number , GCP ID number is outputted to the file of the GCP ID number list.
