Edgetech USBL BROADBAND ACOUSTIC TRACKING SYSTEM, User Hardware Manual, Page: 91 / 102

5-1
5.0
OPERATION
In either Pinger or Transponder/Responder mode, the relative bearing and Depression Angle of the
tracked target(s) are determined by measuring the phase differences of the sound waves for each
hydrophone element. The Target Bearing, measured in degrees, is relative to Hydrophone Heading. The
Depression Angle is formed by the intersection of a Horizontal Plane and a line drawn from the Vessel
Reference Point to the target. Once these values are determined, other positioning parameters can be
calculated.
NOTE: ‘Vessel Reference Point’ is the relative point from which all
measurements are calculated. The position of the Vessel Reference Point
is determined by hydrophone offsets entered into the Tracking System,
illustrated in
Figure 5-1
.
If no offsets are entered, the hydrophone becomes the Vessel Reference
Point.
Figure 5-2 illustrates the system’s calculated positioning
parameters.
The slant range is the straight-line distance from the Vessel Reference Point to the target. When a sound
source other than a pinger is used, the travel time of the sound wave between the sound source and the
hydrophone is used to calculate the slant range directly. The Horizontal Range (HR) is the projection of
the slant range on a horizontal plane.
In PINGER mode, (HR) is calculated by:
(where Z is target depth and
β
is Depression Angle)
𝐻𝐻𝐻𝐻 =
𝑍𝑍
𝑚𝑚𝑡𝑡𝑡𝑡
β
Equation 2
Slant range (SR) is calculated by:
(where Z is target depth and
β
Depression Angle)
𝑆𝑆𝐻𝐻 =
𝑍𝑍
𝑠𝑠𝑠𝑠𝑡𝑡
β
Equation 3
In TRANSPONDER or RESPONDER mode, slant range (SR) is calculated from the known speed of sound in
the water column (V), the transponder or responder turnaround time (D) and the measured time (T)
between transmitted pulse and received reply by: