DAVIS PROTRACTOR TRIANGLE User 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 91/8” x 65/8” x 65/8” (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 anoth­er 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 over­lamination 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 [phone] • Fax [phone]

[e-mail] www.davisnet.com

062_Inst.pdf October 2005