Geoscience Reference
In-Depth Information
have proposed the use of low cost GPS L1-only monitoring receivers (Chen
2001
;
Roberts
2002
). The shortcoming of this approach is the fact that, unlike the dual-
frequency data, the single-frequency GNSS receivers' data cannot be corrected for
ionospheric delay (Rizos et al.
2010
). Research on the development of low-cost
RTK GPS deformation monitoring systems for landslide monitoring application
are ongoing (e.g. Aguado et al.
2006
; Brown et al.
2006
; Glabsch et al.
2009
;
Verhagen et al.
2010
;Yu
2011
).
In this chapter, a new landslide deformation monitoring concept that uses
RRTK principle is being proposed. The unique advantage of the RRTK approach
is that low-cost receiver hardware can be deployed for field data streaming since
the responsibility of complex computations is shifted from the roving receivers to
the control centre.
This chapter is organized as follows. In
Sect. 2
, the server-based processing
technique is discussed. In
Sect. 3
, an overview of GPS/GNSS Continuously
Operating Reference Stations (CORS) is presented. In
Sect. 4
, the real-time GPS
data streaming using Networked Transport of RTCM via Internet Protocol (Ntrip)
is described.
Section 5
presents the experimental data collection and processing.
The results and analyses are presented in
Sect. 6
. Finally, the summary, outlook
and field challenges are presented in
Sect. 7
.
2 The Server-Based Processing Technique
The conceptual framework of this study is based on the server-based RTK pro-
cessing concept. According to Feng et al. (
2009
), the server-based RTK processing
concept can be used in various RTK techniques (see Fig.
1
)—precise point
positioning (PPP), standard single-baseline RTK, network-RTK (NRTK), reverse
single-baseline RTK (RRTK), and reverse network RTK (RNRTK).
The last two techniques (RRTK and RNRTK) combine the server-based pro-
cessing concept and two-way communication for the computation and transmis-
sion of the user's accurate position. The reverse technique, which technically alters
the one-way communication flow in the conventional RTK technique, involves a
two-way communication (see Fig.
2
) which requires the field users to transmit
their raw observations to a control centre for the computation of the position
solution, after which the computed solution along with the quality control indi-
cators are transmitted back to the field users.
The reverse approach based on combining the server-based processing concept
and two-way communication has evolved for over 5 years now. But research
opportunities offered by this approach is still not adequately exploited. The first
practical implementation of RNRTK was made by Nippon GPS Solution in Japan
(Kanzaki
2006
). Rizos (
2007
) proposed the development of new business model
using the RNRTK approach, with the main goals of placing the control of the
products with the service providers and enhancement of commercial value on the
service. A new framework for RNRTK using distributed-computing technique was
