Home' Position : Position Apl May 2016 Contents height, the CORSnet-NSW Adjustable
Antenna Mount (CAAM) was developed
and patented by LPI specifically for use
All Tier 3 CORSnet-NSW CORS
installations since March 2011 use the
CAAM, which has proven to be very
effective and particularly invaluable when
replacing or upgrading GNSS antennas
because a zero antenna height is always
maintained. This design is freely available
to other CORS operators.
CORSnet-NSW uses a mix of modern
Leica and Trimble GNSS receivers,
tracking both GPS and GLONASS
satellites. LPI has specifically avoided the
exclusive use of only one type of receiver
to minimise risks and increase business/
service continuity. Diversification has
been limited to two brands in order to
simplify fleet management.
The NSW Foundation Spatial Data
Framework (FSDF) 2020 Strategy directs
CORSnet-NSW to support new GNSS
constellations and signals. More than half
of all CORS are hardware-ready for (or
at least capable of) tracking additional
GNSS constellations such as Galileo and
BeiDou in the future.
This functionality will be activated by
CORSnet-NSW only when each system
officially reaches its Initial Operational
Capability (IOC), system reliability has
been proven and there is sufficient user
demand. In the meantime, BeiDou
satellites are currently tracked at six Tier 2
CORS and 62 Tier 3 CORS for research and
evaluation purposes. This is particularly
important given Australia’s strategic
geographic position on the globe, resulting
in a multitude of satellite constellations
being available in this region (see Figure 4).
CORSnet-NSW infrastructure has
recently been used in proven trials of
Precise Point Positioning (PPP) solutions
delivered by the Japanese Quasi-Zenith
Satellite System (QZSS) for precision
agriculture applications in rural NSW.
This was a small but significant first
milestone in NSW’s desire to introduce
satellite-based delivery (through either
premium resellers, National Positioning
Infrastructure – NPI, international
coordination or other mechanisms) to
service new and emerging market sectors
and realise LPI’s aspiration to improve
service delivery through new technologies.
CORSnet-NSW uses a mix of high-
precision survey antennas (69%) and
Dorne Margolin choke ring antennas
(31%), generally with radomes installed.
LPI intends to have future antennas
individually calibrated by Geoscience
Australia at its new test facility in Canberra.
The majority of CORS feature dual
communications (main and backup, e.g.
ADSL and Next G) to ensure the highest
possible standard in regards to data
availability and data completeness. Installs
are equipped with a variety of auxiliary
devices such as industrial-strength modems,
remote reboot relays, digital cameras with
selective motion detection, door alarms,
automatic cooling fans, solar power (on
selected sites) and Uninterruptible Power
Supply (UPS) units that last up to 30 days.
This is complemented by two mirror-
image Network Control Centres (NCCs),
located in Sydney and Bathurst, that
utilise Commercial-Off-The-Shelf (COTS)
CORS management software with full
redundancy. ICT architecture allows for
immediate failover between the two NCCs
to ensure continuous data supply to users.
The data centres employ server
virtualisation technology to maximise
hardware utilisation, flexibility and
scalability while at the same time
minimising power consumption, space
requirements and carbon footprint.
Network connectivity and availability is
constantly monitored using external service
providers. A third, ad-hoc development
system is used for internal system testing.
Quality control and integrity monitoring
of CORS infrastructure is becoming
increasingly important for legal traceability
of data and measurements as well as
for long-term stability studies of station
coordinates. CORSnet-NSW operation
and performance is monitored by LPI staff
in real-time using Trimble’s Pivot CORS
network management software, which
also has the ability to detect abrupt station
movement in real-time.
Long-term, multi-year station stability
monitoring based on daily 24-hour
RINEX files is performed in-house using
the scientific Bernese software in an
automated process. Station coordinates
are calculated with millimetre-level
precision, and the resulting time series
are made available on the CORSnet-NSW
website (see Figure 5 for an example).
System performance and station stability
are also independently monitored by third
parties, including premium resellers and
the APREF analysis centres.
The stability of all Tier 2 CORSnet-NSW
pillars is monitored by LPI at suitable
intervals through high-precision Reference
Mark (RM) surveys. These terrestrial
surveys determine the horizontal position
of the pillar relative to three surrounding
reference marks with an accuracy of better
than 1 mm (95% confidence interval) and
the vertical position of the pillar plate to
within class L2A specifications (maximum
misclose 2√d mm - see Position 44,
Figure 3: Typical CORSnet-NSW
monumentation and auxiliaries
at (a) Tier 2 and (b) Tier 3 sites.
Figure 4: Number of visible
GNSS satellites above 30o
elevation expected in 2020
(courtesy Prof. Chris Rizos).
36 position April/May 2016
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