Global Positioning System Reference
In-Depth Information
mm
(a)
90
8
60
6
30
0
4
-30
2
-60
-90
0
-180
-120
-60
0
60
120
180
Longitude (
o
)
mm
(b)
90
8
60
6
30
0
4
-30
2
-60
-90
0
-180
-120
-60
0
60
120
180
Longitude (
o
)
Fig. 8. Diurnal variation amplitudes (mm). (a) from GPS-derived ZTD and (b) from COADS
surface pressure data adjusted by a scale factor (2.28 mm/hPa)
component ZHD accounts for approximately 90% of ZTD, ZTD is strongly correlated with
surface pressure p0 at the site. It can be seen that if subdiurnal surface pressure varies by 1
hPa, the scale factor predicts a subdiurnal ZTD variation with amplitude of 2.28 mm. The
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