Abstract
For many purposes it is required to k now the actual range at which an object of some definite area and shape can be recognized. If the proper value can be given to the liminal contrast (=0.02), we can compute the visual range. For this purpose it is necessary to measure the extinction coefficient a and the contrast C of two adjacent surfaces. The main concern is the characteristics of the human eye and the optical parameters of the atmosphere. The visual range can be calculated from the transmittance and the distance of 0.15 km between the projector and the telephoto meter will limit the liminal visual range up to 4-5 km, so that for the longer visual range (10 km or more) it is necessary to investigate not only the transmittance but the reduction rate of contrast between the objects and their backgrounds (by contrast meter and telephoto meter). In this paper the instruments, some experimental results and the method s of the determination of the visual range are described. An ITV camera is now largely used for monitoring the field view and the information can be telemetered through the narrow band telephone line. Usually the camera eye has different characteristics from the human eye. So that it is necessary to investigate the relation between actual view and camera image under different optical conditions by means of the measured value of the visual range.
