Global Positioning System Reference
In-Depth Information
In the presence of measurement errors, the range rings used to compute the
user's location will be in error and result in error in the computed position. The con-
cept of dilution of precision is the idea that the position error that results from mea-
surement errors depends on the user/foghorn relative geometry. Graphically, these
ideas are illustrated in Figure 7.5. Two geometries are indicated. In Figure 7.5(a),
Variation in range ring
due to range errors:
from foghorn 1
from foghorn 2
Shaded region: Locations
using data from within
indicated error bounds
User location
Foghorn 1
Foghorn 2
(a)
Shaded region: Locations using data
from within indicated error bounds
Variation in range ring due to
range errors:
from foghorn 1
from foghorn 2
User location
Foghorn 2
Foghorn 1
(b)
Figure 7.5 Relative geometry and dilution of precision: (a) geometry with low DOP, and (b)
geometry with high DOP.
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