IEEE Instrumentation & Measurement - September 2023 - 45

Table 2 - Detailed information of time links receivers
Station/ID Organization
NTTS
Receiver
NTSC
NT07
TLM2
USUD
CUSV
NTSC
TL
IGS
IGS
SEPT
POLARX5
SEPT
POLARX5
SEPT
POLARX5
SEPT
POLARX5
JAVAD TRE_3
DELTA
Clock
External
External
External
External
H-Maser
Internal
3
6
9
086
12
-22
-20
-18
-16
-14
-12
086
088
090
092
DoY
Fig. 3. NTTS clock offset using the GBM product for 11 days from DoY 86 to
96 in 2022.
PPP-B2b tracking stations are only in the territory of China. As
a result, it is apparent that the time comparison of BDS-3 and
BDS-3 + GPS PPP-B2b is better than that of a single GPS system.
The content of this study is mainly based on BDS-3 and
BDS-3 + GPS.
The zero-baseline CCD result is displayed in Fig. 5.
The CCD result sequence of SF PPP-B2b fluctuates within
0.2 ns. The STD value of the CCD result residuals was
calculated, and results showed that the addition of GPS
system failed to improve the accuracy of SF PPP-B2b time
transfer.
Long-baseline PPP-B2b Time Comparison
Taking the DF GBM time comparison as a reference, the differences
among the long-baseline time comparison results are
shown in Fig. 6 and Fig. 7. Meanwhile, Table 3 lists the STD
values of the residuals. Combining Fig. 6, Fig. 7 and Table 3,
two conclusions have been drawn. First, taking the GBM time
comparison as a reference, the PPP-B2b time comparison residual
for all three links fluctuated within 2 ns. Furthermore,
the receiver clock offset introduces the hardware delay which
led to a constant deviation in different time links. The STD
values of the time comparison residual of SF PPP-B2b were
September 2023
094
096
-3
3
6
9
086
-20
-16
-12
-8
-24
-28
-32
086
088
090
092
DoY
Fig. 4. PPP-B2b NTTS clock offset (GPS + BDS-3, BDS-3, GPS from top to
bottom) for 11 days from DoY 86 to 96 in 2022.
concentrated at 0.5 ns. Second, regardless of the three-time
comparison long-baseline links of PPP-B2b, it could be observed
that the addition of GPS system did not improve the
accuracy of time comparison.
Conclusions
The emergence of the PPP-B2b product promotes the application
of real-time PPP in positioning in a networkless
occasion. Meanwhile, the PPP-B2b product broadcast by
three GEO satellites solves the problem of interruption
caused by network fluctuation in the field of real-time PPP
time comparison. The treatment of ionospheric delay of SF
PPP-B2b is crucial, and a GRAPHIC SF PPP-B2b model is proposed
and validated to keep PPP-B2b network-independent.
Considering that the PPP-B2b product serves GPS and BDS
users in the Asia-Pacific area, two TAI laboratories (NTSC,
TL), an external atomic clock station (USUD) and an IGS
IEEE Instrumentation & Measurement Magazine
45
094
096
088
090
092
094
096
088
090
092
094
096
12
15
Clock offset (ns)
Clock offset (ns)
Clock offset (ns)
Clock offset (ns)
IEEE Instrumentation & Measurement - September 2023

Table of Contents for the Digital Edition of IEEE Instrumentation & Measurement - September 2023
