Measuring Deformation Through Radar Imaging

1
Measuring Deformation Through Radar Imaging
Herbert Pablo, Dr. Glen Mattioli, Dr. Pamela
Yansma
University of Arkansas, Fayetteville, Arkansas
72701
Introduction Geologists have looked a long time
for a technology good at measuring extremely
minute changes over a large area. While they have
had models for what happens to the Earths
surface after an Earthquake or before a volcano
eruption, there was absolutely no way to test
these models. That is of course until the arrival
of a new technology known as Interferometric
Synthetic Aperture Radar imaging (InSAR).
Procedure

• Getting from raw satellite data to an
  interferogram is not a easy process. Luckily,
  there is a software program known as ROI_PAC or
  Repeat Orbit Interferometric Package which helps
  a lot with this procedure. Using this software
  package there are just a few simple steps that
  must be followed.
• Acquire 2 frames of ERS Data collected at
  different times from the same location.
• Acquire orbital data for orbits in question.
• Acquire a digital elevation model for area in
  question
• Set up environment variables
• Condition the raw data
• Run through ROI_PAC

Figure 2- 3-Dimensional look at how the radio
waves are emitted.
Interferogram
The data obtained from the ERS satellite and
others is mainly used to create an interferogram
like the one showed in figure 1. An interferogram
is actually a combination of 2 images of the
exact same area with a time elapse in between.
When these images are overlaid the change in
phase shift can be color coded and will then show
the deformation of a given area.
Figure 1- interferogram of the 1992 Landers
Earthquake
What is InSAR?

• Method using an orbiting satellite that emits
  and receives radio energy in the form of waves
• Carries two types of information.
• Terrain information carried in strength and
  intensity of signal
• Changes in roundtrip distance seen through phase
  changes of the radio waves.

Application
This process will be used specifically to measure
water loss in Eastern Arkansas and Volcano
deformation in the lesser Antilles.
Acknowledgments
Henry L. Turner, Daniel Hawkins
Figure 3- shows how the colors on an
interferogram reflects changes in elevation.