Specifications

BATS AND PORTABLE BATS PRINCIPLES OF OPERATION
4-2
source and the hydrophone is used to calculate the slant range directly. The horizontal range is
the projection of the slant range on a horizontal plane.
In PINGER mode, horizontal range (HR) is calculated by:
Z
HR =
tan 
where Z is the target depth and  is the depression angle.
Slant range (SR) is calculated by:
Z
SR =
sin 
where Z is the target depth and  the depression angle.
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 meas-
ured time (T) between transmitted pulse and received reply by:
SR = V x (T - D)
2 in transponder mode, and:
SR = V x (T - D) in responder mode.
Horizontal range (HR) is calculated by one of three methods, depending on the calculated value of
the depression angle () from the horizontal and the depth MODE.
A. In CALCULATED depth MODE and when the target is within a 90 degree cone (value of ()
greater than 45 degrees), horizontal range (HR) is calculated by:
HR = SR cos 
This is the normal situation, where the target is within a 45 degree angle from the vertical axis of
the hydrophone.
B. In CALCULATED depth MODE and outside a 90 degree cone (values of () less than 45 de-
grees), as the target moves to positions which are between the hydrophone horizon and a
45 degree depression angle, the measured accuracy degrades due to physical constraints of
the measuring hydrophone. (As the target approaches the horizon, the angle becomes un-
measurable.) In this situation, the input target depth (Z) (manual, analog or telemetry) is
used to calculate horizontal range by:
Z