Corner Reflector Interferometry (CRInSAR)
revolutionises the precision movement surveying of pre-determined
locations and structures. Using in-situ radar corner reflectors,
millimetre measurements of displacement can be made from spaceborne
satellites.
Features of CRInSAR
Monitor the movement of specific structures
and locations
Obtain measurements every satellite orbit e.g.
24 days
Millimetre line of sight accuracy
No ground survey costs
CRInSAR uses conventional radar corner
reflectors secured to the feature to be monitored. NPA
can efficiently supply such units.
Corner Reflector Interferometry (CRInSAR) makes measurements
from radar satellites to point target radar corner reflectors
that are secured to the feature on the ground to be monitored.
Corner reflectors are deployed in arrays to derive relative
displacements between successive radar satellite image acquisitions
(every 24 days with RADARSAT or 35 days with ERS or ENVISAT).
CRInSAR is ideal for monitoring reservoirs, dams, pipelines,
bridges, individual buildings, or suspected areas of instability,
e.g. across faults and unstable slopes.
Radar corner reflectors are simple trihedrals of aluminium
that strongly reflect the radar signal back to the satellite.
As the feature to which the reflector is mounted moves between
successive radar acquisitions, a difference in radar signal
phase between the satellite and the corner reflector is registered.
Conventional interferometric processing then computes actual
line of sight movement.
NPA can efficiently source inexpensive corner reflector units
as required.
In a project funded by the European Space Agency,
NPA were working with Thames Water, the world's third largest
water company, using corner reflector interferometry to monitor
the displacement of retaining banks associated with water
volume in their West London reservoirs. Seven inexpensive
reflectors were deployed around the Wraysbury reservoir near
London.
