Designing the configuration

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Designing the configuration of the
Geodetic-Geodynamic Network in Israel
Gilad Even-Tzur Department of Mapping and
Geo-Information Engineering Faculty of Civil and
Environmental Engineering TECHNION - Israel
Institute of Technology
ISGDM-2005, 17-18 March, Jaén , Spain
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The Geodetic-Geodynamic Network (G1)
? Includes 160 points that homogeneously cover
the state of Israel (Blue circles and Red
squares) ? The location of the points was
determined mainly according to geological
considerations ? The points were built according
to very high technical specifications, to ensure
their geotechnical stability
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The goal of the Geodetic-Geodynamic Network
? A potential geodetic network for monitoring
deformations in primary and secondary known
faults ? Serves as the major geodetic control
network of Israel
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The First Measurement Campaign
? During 1996 the G1 network was measured for the
first time ? The network was measured by four
GPS receivers ? Sessions of 24 hours ? Most
network points were measured in two independent
sessions ? The data processing was carried out
using the BERNESE
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The Network Sensitivity
? Based on the first campaign, a sensitivity
analysis was performed in the northern part of
the network ? The analysis indicated that the
sensitivity of the network was too low ? The
analysis also indicated that an identical second
measurement campaign will not be sufficient to
detect possible movements and deformations
A new network design is needed
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Network Configuration of the Second Campaign
? The second campaign was held in 2002 ? Only
100 points were measured (Blue circles) ? 5 new
points were fixed in the northern part of the
network (Yellow circles ) ? 11 continuous
permanent GPS stations were operated (Green
triangles)
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Vector Configuration Design of the Network
? An effective design of the GPS measurements
decreases campaign costs and increases the
accuracy and reliability of the network ? The
goal of the design is to improve the network, so
that it would enable the detection and
measurements of expected movements and
deformations ? A method, based on sensitivity
analysis, was used for the GPS vector
configuration design ? The method uses a velocity
field of the network points, calculated from an
assumed geological model
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Geological Model
? Locked Fault model in the Dead Sea Rift the
fault is locked from the surface down to depth D,
and slips freely below this depth by V
millimeters per year
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Sensitivity Analysis
? Based on statistical test of Hypothesis
? If is true, the test statistic has a
non-central F distribution with non-centrality
parameter l given by
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Sensitivity Analysis
? We define as the boundary value of ?,
which will cause the null hypothesis to be
rejected at probability levels a and ß, the value
is an implicit function
? Our aim is designing a monitoring network,
which will enable the rejection of the null
hypothesis and the acceptance of the alternative
hypothesis ? Sensitive Network
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Sensitivity Analysis
? Since the first GPS campaign has already been
carried out in 1996 N1 has been defined ? We
create the normal matrix N2 which contains the
sessions with the most effective contribution to
the sensitivity of the network
8 sessions provide a sufficiently sensitive
network
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Configuration Design of the Network
? To increase the reliability of the network,
each point was measured in three independent
sessions ? The duration of each session was
planned for 8 hours with epoch interval of 30
sec ? The network was designed for measurements
using four receivers
92 sessions for 105 points
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The designed sessions of the northern part of the
Geodetic-Geodynamic network
Broken lines - The eight sessions that provide
sufficiently sensitive network
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The ability of the network to sense horizontal
velocity
The typical precision of the network points ?
1996 3-4 mm for the horizontal component ? 2002
2-3 mm for the horizontal component
We can roughly estimate the ability of the
network to sense horizontal velocity along the
Dead Sea rift for a velocity of two millimeters
per year