Screen Cursor - Interphase Color Twinscope Operation Manual

Important Note: One of the biggest problems encountered
with adjusting forward scanning sonars is too much gain -
especially in the vertical forward view. If there are no targets
directly in front of the boat, the natural tendency is to continue
to increase the gain. Usually this results in a noisy display and
is not necessary. In general, if you can see the bottom between
3 and 4 times the depth forward (for example in 10 feet of
water, seeing the bottom forward 30 to 40 feet) the gain is
adequate. (On forward ranges below 200 feet, it's
recommended to keep the gain below the number 10.)

Screen Cursor

The Color Twinscope has a useful screen cursor feature that
can show the approximate depth and range from the vessel to
any target on a forward scanning display.
Pressing the CURSR button will toggle the screen cursor and
it's CURSOR DATA BOX on and off. The drawing at right
shows a forward horizontal scan display with the CURSOR
activated and the CURSOR DATA BOX in the lower right
corner of the display.
To use the screen Cursor feature, press the CURSR button to
activate and then use the NAV button to move the cursor to the
desired location on the display. Wherever the cursor is placed,
the CURSOR DATA BOX will display the approximate
RANGE, DEPTH and BEARING (if in the horizontal
scanning mode) from the vessel to that location.
It is important to realize that the depth and bearing information
in the CURSOR DATA BOX is the result of a calculation
based on the angle of the acoustic beam below the surface of
the water. Because each transducer installation is unique and
the vessel may be moving up and down in the water - the angle
of the acoustic beam is only approximately known. Therefore,
the calculated depth is also only an approximation and should
not be relied upon during critical situations.
It is also important to understand that the calculated depth in the
CURSOR DATA BOX is the depth at the center of the Color
Twinscope's 12-degree acoustic beam angle as shown in the
diagram at right. Notice that the beam expands as it gets further
from the boat. For example, at 1,000 feet the beam angle has a
diameter of greater than 100 feet! However, the cursor
calculates the depth at the centerline of the beam as shown.
10 Ft
FORWARD LOOKING SONAR
FORWARD LOOKING SONAR
Cursor
FORWARD LOOKING SONAR
Use Nav Key to Move Cursor
CURSOR DEPTH AND RANGE
12-Degree
Beam Angle
27
CURSR PWR
30 to 40 Ft
VERT HORIZ
DATA
DOWN
RANGE GAIN
CURSR PWR
VERT HORIZ
DATA
DOWN
RANGE GAIN
BEARING -30deg
RANGE 65 Ft
DEPTH 12 Ft
Cursor Data Box
CURSR PWR
VERT HORIZ
DATA
DOWN
RANGE GAIN
BEARING -30deg
RANGE 65 Ft
DEPTH 12 Ft
Surface
Depth
Range