80 seamanship secrets
- Measure 32.2 miles on the chart’s right- or left -hand latitude scale with your
plotting compass. Stick the compass needle point into the mark at the top
of Angel Island and sweep an arc at 32.2 miles across the TR. If the distance
is too long for the compass, measure a convenient number of miles and walk
the compass back along the TR. For instance, if you measure 5 miles, you
would walk the compass back 6 full segments (30 miles), plus an additional
2.2 miles. - Estimate your time to that intersection point, label the chart, and set the
GPS alarm. When the alarm sounds, scan the horizon with binoculars for
Angel Island. In clear weather, Angel Island should appear nearly dead
ahead on the horizon.
Secrets of the Most Accurate LOP on Earth
When two charted objects line up as viewed from your boat—say a church spire
behind a tank—you have a range (also known as a transit). A range provides a
fl awless line of position (LOP). When planning a cruise, look ahead, behind,
and to the sides of your track for pairs of charted objects that will line up as you
proceed. Natural ranges help you stay on track, show your boat’s speed of advance,
and strengthen the quality of any position fi x. You can use any combination
of landform tangents, landmarks, beacons, and buoys as a range. You needn’t
Th e mountains of Angel Island, which the chart shows to be 300 and 500 feet above sea
level, could be used as a prominent landfall.