Triton TargetPro - Manual (Page 35)

June 2004 TargetPro™ User's Manual
3.3 Height
Such objects cast an acoustic shadow on the side facing away from the towfish.
The length (or across-track width) of this shadow can be used in combination
with the fish altitude and horizontal distance from the fish to derive height
information.
Height is the magnitude to which an object stands above
the seabed. The Measurement Tool’s Object Shadow
function (shown here at the side of the page) is used to
draw a line in imagery.
The computational method assumes that the target is a thin, vertical object. As
such, the height formula is:
Height = FishAlt * L1/(L1 + L2)
Figure 11. Height from fish altitude, shadow lengths and distances
Note: The shadow occurs on the left of the contact for a port channel and on the
right of the contact for a starboard channel.
A negative range in the Cursor Status window indicates a port-side image, and a
positive range indicates a starboard-side image. A separation of the shadow
from the contact indicates that the contact is moored (that is, not in contact with
the seabed).
Chapter 3: Measuring a Contact 26