Precise Orbit Determination of Global Navigation Satellite System of ...

Chapter 4 Major Error Sources of Satellite Observations
Pseudorange Error(m)
Pseudorange Errors(m)
80
60
40
20
0
-20
-40
-60
-80
25
20
15
10
5
0
-5
-10
-15
-20
-25
0 50 100 150 200 250 300 350 400 450
M ultipath De lay(m )
Figure 4-2 Multipath Error Envelope for GPS Code Pseudoranges
38
C/A Code
P Code
0 50 100 150 200 250 300 350 400 450 500 550 600
M u ltip a th D e la y (m )
Figure 4-3 Periodic Function of Multipath Error
4.2.2 Influence of Multipath Errors on Range and Phase Observations
From the mathematical point-of-view, the influence of multipath delay δ on correlation time τ ′ can be directly
derived from auto-correlation function R( τ ) .
Using very simple signal equation, suppose the arrived signal from satellite is
S d
= A cosω ( t −τ
)
where
τ time delay from the satellite to the receiver
One multipath signal reflected from near object is:
S m
= αA cos[ ω(
t −τ
−δ
)]
C/A
P
(4-31)
= α A cos[ ω(
t −τ
) + θ m ]
(4-32)
where
α multipath relative amplitude coefficient < 1;