Las Vegas is selected because of the
expected high spatial coherence over long time.
This enables a cross-comparison with conventional
interferometry.
The expected displacement signal is considerable
and well monitored due to the vicinity to the
Hoover Dam and the large population. The displacement
is caused by water loading and ground-water
control (withdrawal). The maximum subsidence,
located in the center of the Valley is more than
two meters since 1935. The expected atmospheric
signal is large, which has been supported
by the created differential interferograms. The
topographic signal is large for
the surroundings of Las Vegas, but the DEM errors
are expected to be relatively small for the city
area (but note that the height of the buildings
may cause DEM errors for the positions of the
PS points).
The estimated linear displacement rates correspond
well to the known features described in literature
and agrees with the mean line of sight displacement
rate for the NW bowl, estimated ca. -20 mm/year.
Figure 18: Estimated linear displacement
rate for selected pixels with test below 3.0 (92507
of 137304 estimated points, ca. 140 points per
km2). Red corresponds to 20 mm/year subsidence,
blue to +20 mm/year uplift, relative to the reference
point (the asterisk).
