Global Positioning System Reference
In-Depth Information
(a)
Hou
r
90
24
60
18
30
0
12
-30
6
-60
-90
0
-180
-120
-60
0
60
120
180
Longitude (
o
)
(b)
Ho
ur
24
90
60
18
30
12
0
-30
6
-60
-90
0
-180
-120
-60
0
60
120
180
Longitude (
o
)
Fig. 9. Time of diurnal peak values at local time (LT: hour) where at each GPS sites longitude
the Sun is at its highest elevation at 12:00 LT. (a) from global IGS GPS observations and
(b) from COADS surface pressure data
GPS-derived S1 and S2 signals in ZTD are compared with three-hour surface synoptic
pressure observations from 1997 to 2007 that are archived at the National Center for
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