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.
 
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