Problems Associated with Navigation, Continued
Knowing the direction between two positions makes it possible for the
navigator to lay a course from where he is to where he wants to go and
then to proceed to that point. Direction will be presented in greater
detail later in this chapter.
The distance between two points is the physical separation without
regard to direction. Nautical distance is measured as the international
nautical mile (nmi) of 6, 076.1 feet. The nmi is longer than the statute
mile (mi) used on land, 5, 280 feet; 1.15/1 is a simple ratio often used
to convert nmi to mi.
Time in navigation is always based on the 24-hour clock. You are
already familiar with this type of timekeeping as it is what we use in the
Speed is defined as the rate of movement. In navigation speed is
referred to as nautical miles per hours or knots (kn).
We can now put this all together. We have defined the major problems
associated with navigation. The solutions
contained in later text. We know that the
position, direction, and distance to travel. But how does speed and time
figure in this picture?
to these problems are
navigator must determine
That brings us to the time, speed, and distance triangle. If you know the
distance you need to travel and at what speed you will proceed, you can
use simple mathematics to determine how long it should take to travel
that distance. This is a triangle, because if you know any two values
(time, speed, or distance) you can solve for the unknown value. That
brings us to the next subject.
Where does this information go? How
does one actually go from one known position to another known
position safely? The answer is the nautical chart! The remainder of this
chapter will explore the nautical chart and how the QM uses it.