Edgetech 2000-CSS, Руководство пользователя

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2-7
a. Vertical resolution is the smallest distinguishable distance between the peaks of two reflections that can be
displayed on the screen as separate reflectors. Sound energy is reflected back to the sonar system when the
transmitted pulse encounters a change in density. The resolution of a sonar system is measured by its ability to
distinguish between two adjacent targets. The vertical resolution is dependent on the transmitted chirp pulse
bandwidth. It is theoretically calculated by the product of the transmitted pulse length (inverse of the bandwidth)
and half the speed of sound in water (approximately 750 m/s). For example, a full bandwidth pulse from an SB-
424 Towfish has a vertical resolution of 3.75 cm (1/20,000 x 750).
b. The value for sub-bottom penetration is the maximum distance beneath the sea floor that a step change of 10%
in density can be seen on the sub-bottom display. This assumes that the sediment is gas free (no organic materials),
that the lowest frequency of the pulse spectrum is transmitted and that the vehicle is within 5 meters of the seabed
(range for maximum penetration). Lower frequencies reduce attenuation (absorption of sound). Towing the
vehicle close to the sea floor reduces the acoustic footprint thereby reducing scattering (interfering reflections)
from the sea floor and within the sediments.
c. At the -3 dB points, depending on the center frequency.