DAVIS Hand Bearing Compass - Manual

INSTRUCTIONS
Davis Hand Bearing Compasses are excellent for yachtsmen, racers, and fishermen as
an aid to position finding and steering. The instruments let you easily obtain quick mag-
netic bearings on shore or floating objects. Simply align front and rear sights on an object
and read off bearing. Use to take a quick bearing or position set, determine angular gain
or loss on the competition while racing, check distance offshore, establish lee-bow set
while cruising or racing in currents, determine drift vector, and plot a line of position.
All Hand Bearing Compasses feature stable, liquid-damped compass card graduated in
5° segments. Bold graduations every 15° for easy reading. Lightweight design for easier
bearing. High impact plastic housing. Lanyard included.
The Illuminated model has solid-state LED ( Light Emitting Diode) illumination system
which floods the compass capsule and sight vane with soft light. The LED will last for the
lifetime of the compass. Batteries, which are included, will last up to 10 times longer than
with regular bulbs. Average LED “half-life” is approximately 10 years if operated continu-
ously. The compass has a positive “push-on” switching action, with vinyl boot water pro-
tection. Battery housing has high watertight integrity.
Compasses are designed for Northern Hemisphere only.
Sighting Objects. Hold the compass in a relaxed position at
arms length, with the yellow cursor line facing you. With the com-
pass slightly tipped so both pointers are visible, rotate your arm and
upper body until both pointers are in-line with the object being sight-
ed (figure 1). Read the magnetic bearing as it appears at the yellow
cursor line.
Note: Standing near large metal objects will affect the accuracy of
your magnetic bearing.
Navigating Using Your Sightings. A line of position (LOP)
is simple to obtain (figure 2). Find an object that is easy to identify
on a chart and take a sighting to determine its magnetic bearing.
Draw a line from the object using its magnetic bearing and you know
that you are somewhere along that line of position. Take a sighting of
another object and plot its line of position. Your position is where the
two lines cross (figure 3). Tip: Three sightings plotted on the chart
(three LOP's) is even more accurate and these sighting form a trian-
gle when plotted; you are somewhere inside that triangle.
Plotting Distance Offshore. This is easiest and most accu-
rate when your compass course is roughly parallel to the shoreline.
You must also know your speed over ground. Note the exact time
that you are abeam of (perpendicular to) or 45
° off a prominent
object on shore like a lighthouse, smoke stack or radio tower. Take
the exact time again when you are perpendicular to or 45 ° off the
object. Plot these sightings on the chart and, with your distance run
as one leg, you have a right triangle (figure 4). Your speed multiplied
#211 Standard
#215 Illuminated