Global Positioning System Reference
In-Depth Information
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[23
Fi
gure 7.3 Relative vertical antenna phase variation calibration at NGS.
(Data Source:
Gerry Mader, NGS.)
Lin
—
1
——
Lon
PgE
an
d azimuth. This real-time calibration uses undifferenced observations from the
te
st antenna that are differenced over very short time intervals. The intervals are
su
fficiently short so that multipath is eliminated in the differencing. This calibration
te
chnique therefore becomes site-independent. Rapid changes of orientation of the
ca
libration robot allow the separation of PCV and any residual multipath effects.
Se
veral thousand observations are taken at different robot positions. The calibration
ta
kes only a few hours. Figure 7.4 shows the results of the absolute calibration for the
A
OAD/M T choke ring antenna.
[23
Absolute PCV of AOAD/M T antenna.
The PO are
n
PO
=
0
.
6
,e
PO
=−
Fi
gure 7.4
0
.
5
,
u
PO
=
91
.
2, and
(
−
0
.
1
,
−
0
.
6
,
120
.
1
)
millimeters for L1 and L2, respectively. (Data from
NGS, 2002.)
