High Quality Reception and Evaluation of Images from GMS
Youxin Lu, Akio Yasuda, Kohji YAMASHITA · The Journal of Japan Institute of Navigation · 1992
The images of Weather Facsimile, sent through GMS, have 64-leveled gradation, which is proportional to the amplitude of subcarrier in the transmitted wave. The authors have designed the apparatus, interconnected with a personal computer, to receive the transmitted images without any loss of the original gradation. The apparatus has received the facsimile under the condition of various values of C/N. 16-leveled gray scale appears in the upper part of the display, graduated every four grades, from 0 to 60. We have evaluated the quality of the received images by calculating the standard deviation σ of amplitude variation of 620 pixels which constitute each scale. The 64-leveled gradation, it has been found out, is ensured when difference between the average values of adjacent scales is not less than 16 times as large as σ. It is also confirmed that the reduction of C/N degrades the quality.