82 seamanship secrets
it, too, crosses the trackline. Now you have a trackline crossed by two bearing
lines, neither which crosses the other. How do you get a fi x from this?
First, fi gure out how far you traveled from 1000 to 1100 at 4 knots. Th e
answer is 4 miles, of course. Now advance—i.e., “run”—that fi rst bearing line of
350 degrees exactly 4 miles along the trackline. Do this with parallel rulers or a
protractor. As in the old Star Trek shows, you want to transport that bearing line
from one spot to another without changing anything about it. Once you’ve done
that, extend the bearing line so that it intersects the second bearing line, and
the point where they intersect is your running fi x. A running fi x is more reliable
than a DR position but less reliable than a fi x based on two or more simultaneous
bearings. Still, when faced with a lack of charted objects for bearings, the running
fi x is a good technique to know.
A running fi x can be needlessly confusing when the bearing lines resemble
the trackline. In the accompanying illustrations you can see how easy it is to
make this mistake, and how simple marking techniques can improve the utility
of a running fi x. A quick glance at the fi rst illustration might convince you that
the boat is in any of four places. In the second illustration, however, the R Fix
is more obvious. Here’s how to improve your running fi x technique:
- Make a bold TR. Start by using a bolder TR. Make the trackline stand out
so you won’t mistake it for a bearing line. Instead of full-length lines of
position (LOP), use short segments that cross the track less than an inch on
each side. Label the fi rst bearing line (taken at 1000) as an EP. - Take the second bearing. At 1100 we take a second bearing. Write the
bearing in your log. Before plotting this second bearing, advance the fi rst
LOP 4 miles along the TR. Th is represents the distance traveled from
At fi rst glance it is diffi cult to tell the location of the 1100 running fi x.