6
TAC
-
100A Revision 6
USING A TAC
-
100A DIVER
NAVIGATION BOARD
Navigating with the TAC
-
100A is simple once you understand the prin-
ciple
“
elapsed time
”
as a method of underwater navigation. The key to
using
“
elapsed time
”
is knowing how long it takes to swim a known dis-
tance in a set frame of time. For example, if you consistently travel 30
ft.(10M) in 20 seconds, then you can estimate the distance you travel
by timing the length of your swim over a given compass heading. To be
fairly accurate, you must set this
“
benchmark
”
by swimming in a normal
relaxed pace.
Once you have established this
“
benchmark
”,
the TAC
-
100 allows you
to plot and follow a predetermined pattern or course for your dive in-
stead of randomly swimming around. To understand how to plot a
course, you must understand how the components of the TAC
-
100A
work together.
Depth and time are tracked on the TAC
-
DG depth gauge and the TAC
-
CHRON Chronometer. Course heading is monitored by the large un-
derwater compass mounted in the center of the TAC100
-
1 navigation
board. The compass card has white luminous digits on a black back-
ground for better contrast in poor visibility, and the three compass rose
points, North, East, and West, are highlighted. An adjustable chem
-
light holder is provided to illuminate the compass for night dives.
Now let
’
s plot a dive to see how the TAC
-
100A really works. We are
able to cover a distance of 30 ft. (10m) in 20 seconds, which is our
benchmark. Using this benchmark, let
’
s plot a dive to a reef that is lo-
cated north of the shoreline, 270 ft.(82m) offshore in 40 ft.(12m) of wa-
ter. In planning this dive, we will explore the reef in a westerly direction
and then return to our entry point.
For the first leg of the dive we will plot a course along a heading of 0°
north for 3 minutes. We should cover a distance of 270 ft. and be on
the reef. Now for leg 2, we will plot a course on a heading 270° west for
10 minutes. This means we cover a distance of 900 ft. while exploring
the reef. After the end of leg 2, it
’
s time to start planning our return to
the entry point. But first, let
’
s plan on exploiting the area between the
reef and shoreline. To do this, we plot our next course heading for leg
3 on a heading of 180° south for 1 minute. This means we will trans-
verse 90 ft (27m) along the bottom toward the shore. Here, we will turn
to a heading of 90° east for 10 minutes which places us back in the
middle of leg 1. Now, all we do is turn to a heading of 180° south and
head for shore.
TAC
-
100A Revision 6
7
By plotting your dives this way, you become much more efficient
underwater and can truly optimize your bottom time. If you have to map
an underwater site, the TAC
-
100A becomes an effective tool for the
job.
TAC100
-
1 NAVIGATION BOARD
The TAC100
-
1 Navigation Board is a rugged high impact plastic board
that is the base for the TAC
-
100A Navigation System. The TAC100
-
2
Underwater Compass, TAC
-
CHRON, and TAC
-
DG/80I or TAC
-
DG/25M are all mounted onto the TAC100
-
1 to complete the system.
The hardware used to mount the TAC100
-
2 Underwater Compass is
made out of non
-
corrosive material and should provide you with many
years of service.
ADJUSTABLE CHEM
-
LIGHT HOLDER
The TAC100
-
1 has an adjustable chem
-
light holder (p/n TAC100
-
1
-
4)
installed above the TAC100
-
2 Underwater Compass. The holder
requires a standard green 6 inch chemical light stick or chem
-
light to
illuminate the compass during night diving. The holder is adjustable
and allows you to control the amount of light that illuminates the
compass. Installation of the chem
-
light is simple.
•
Remove the light tube holder from the round black housing mount-
ed over the compass. Bend the chem
-
light stick until the glass cap-
sule is broken and shake.
•
Now load the chem
-
light stick into the light tube holder and slide the
holder with the chem
-
light back into the housing. To adjust the
amount of light, simply rotate the light tube holder.
