Radar Interferometry
Measurement of Land
Subsidence in Houston, Texas
SAR Data
The Houston area has been
imaged extensively by
ERS-1/2 since mid-1992.
Shown below is an ERS-2 SAR
image of Houston acquired on
January 30, 1996. The
image represents the
radiometrically uncalibrated
amplitude computed from the
complex image. Water
features readily visible are
the Gulf of Mexico in the
lower-right quadrant,
Galveston Bay and Trinity
Bay in the upper-right
quadrant, Buffalo Bayou just
above center and Lake
Houston top center.
The Houston metropolitan
area is located in the
upper-left quadrant of the
image. Houston
Intercontinental Airport can
be seen west of Lake
Houston. The fine dark
lines correspond to roads
with Interstate-610 and
Beltway-8 encircling the
bright response from
buildings in downtown
Houston. The large
industrial complexes and
urban development along
Buffalo Bayou and right of
center in Texas City appear
as bright radar responses.
The general lack of contrast
in the radar intensity over
much of the land area is due
to vegetation. Below
center, the bright radar
responses are agricultural
fields and dark areas are
shallow bodies of water.
Houston ERS radar
image
As can be seen from this
ERS-1/2 one-day tandem
geocoded interferogram,
significant portions of
Houston lie in low-relief
areas with topography
increasing slowly with
distance from the coast.
Each cycle through the color
wheel represents
approximately 30 meters of
topographic relief.
Houston geocoded
topography interferogram
This geocoded
differential interferogram,
spanning the two-year period
from December 26, 1995 to
December 30, 1997, reveals
recent subsidence activity.
The zero-deformation area is
labeled and each cycle
through the color wheel
represents an additional 3
cm of vertical deformation.
A general lack of subsidence
is observed over much of
east Houston while broad
subsidence bowls are
apparent in northwest and
west Houston.
Houston geocoded
differential interferogram
Results
