Global Positioning System Reference
In-Depth Information
The position dilution of precision is defined as
σ
σ
x
1
PDOP
=
+
σ
y
+
σ
z
(
2
.
59
)
The horizontal dilution of precision is defined as
σ
σ
x
+
1
=
σ
y
HDOP
(
2
.
60
)
The vertical dilution of precision is
σ
z
σ
VDOP
=
(
2
.
61
)
The time dilution of precision is
σ
b
σ
TDOP
=
(
2
.
62
)
The smallest DOP value means the best satellite geometry for calculating user
position. It is proved in reference 8 that in order to minimize the GDOP, the
volume contained by the four satellites must be maximized. Assume that the
FIGURE 2.9
Relations to change from spherical to ellipsoidal earth.
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