DAVIS PROTRACTOR TRIANGLE - Manual

#062
The Davis Protractor Triangle includes a protractor
scale for use in tight places (such as the chart tables
on small boats). Combined with a parallel rule, the tri-
angle allows you to plot courses accurately. Essential
for easily measuring right angles, celestial azimuth
angles, and lines of position. The base edge has inch
(1/10th) and centimeter scales. The protractor scale
reads in accurate 1 degree increments or a 32-point
compass scale. Made of durable, flexible and nearly
unbreakable plastic for use on uneven surfaces.
Measures 9 1 / 8 ” x 6 5 / 8 ” x 6 5 / 8 ” (23 x 17 x 17 cm).
TO MEASURE COURSE BEARING:
1) Extend the course line so that it intersects either a
meridian of longitude or a parallel of latitude.
2) If course line intersects a meridian, place the
180° line of the triangle along the course line. Slide
the 180° line along the course line until the center
point of the triangle is at the intersection of the
meridian and course lines. Read the angle at the
meridian. Use the outer scale if you are traveling in
an easterly direction, and the inner scale if you are
traveling in a westerly direction.
3) If course line intersects a parallel, place the 90°
line of the triangle along the course line. Slide the
90° line along the course line until the center point
of the triangle is at the intersection of the parallel
and course lines. Read the angle at the parallel.
Use the outer scale if you are traveling in a
southerly direction, and the inner scale if you are
traveling in a northerly direction.
4) To find magnetic course, add or subtract the local
variation given for your area in the center of the
compass rose on your chart.
OTHER USES OF PROTRACTOR TRIANGLE:
1) Extend a line by sliding one triangle against anoth-
er or against other plotting tools.
2) Lay off bow or beam bearings.
3) Measure distance using handy inch and centimeter
scales on base edge.
Highest quality printing: features sharp printing
process, high gloss finish on front and back, and over-
lamination for durability.
PROTRACTOR TRIANGLE
INSTRUCTIONS
Note: This product was discontinued as a separate
offering in 2005, but may still be purchased as part
of the Davis Charting Kit #083.
3465 Diablo Ave., Hayward, CA 94545 U.S.A.
Phone (510) 732-9229 • Fax (510) 732-9188
[email protected] www.davisnet.com
062_Inst.pdf October 2005