Global Positioning System Reference
In-Depth Information
FIGURE 3.20.
Triangulation error. A baseline
AB
is formed by two forest ranger sta-
tions. The location of a forest fire can be determined by triangulation, but an error
e
in
estimating the angles leads to an uncertainty in the fire location, represented by the
shaded quadrilateral boxes
C
,
D
, and
E
. The size and shape of these boxes depends
upon the size and shape of the triangles. Let us say that a hiking trail (thick line) runs
parallel to the baseline, and so
C
and
D
are both the same distance from the baseline,
yet the uncertainty of their positions is different. A detailed statistical analysis re-
places the ''uncertainty boxes'' by ellipses, as shown surrounding
E
, which illustrate
that we are, say, 50% confident that the fire is within the inner ellipse and 90% con-
fident that it is within the outer ellipse.