polarimetric implications of incidence angle variability for uavsar

Rick GuritzIGARSS Meeting, July 28 2011 1

Rick Guritz, Don Atwood1

Bruce Chapman, and Scott Hensley2

1) Alaska Satellite Facility

2) NASA Jet Propulsion Laboratory

POLARIMETRIC IMPLICATIONS OF INCIDENCE

ANGLE VARIABILITY FOR UAVSAR


UAVSAR

The UAVSAR L-band radar is housed in a pod flown on the NASA G-3

platform, shown here in flight over Edwards Air Force Base, California.


NASA Jet Propulsion Lab’s UAVSAR Instrument

• Reconfigurable L-band, quad-polarimetric SAR

• Developed specifically for repeat track differential interferometry

• Designed to be flown aboard a UAV (Uninhabited Aerial Vehicle)

• Currently being flown aboard a Gulfstream III

• Mission-based data acquisition

UAVSAR


NASA Jet Propulsion Lab’s UAVSAR Instrument

• Reconfigurable L-band, quad-polarimetric SAR

• Developed specifically for repeat track differential interferometry

• Designed to be flown aboard a UAV (Uninhabited Aerial Vehicle)

• Currently being flown aboard a Gulfstream III

• Mission-based data acquisition

• Lacks coverage of spaceborne SAR, but offers higher resolution

and better noise floor. Great data for PolSAR research.

• However airborne platform presents broad range of look angles,

possibly making classification more challenging

UAVSAR


Motivation

• Investigate the affects of incidence angle

variation on polarimetric scattering mechanisms

– As noted by Dr. Lee in his summary talk Tuesday

• Ideal Radiometric Terrain Correction will require

knowledge of terrain type – No current RTC

algorithms address this

• Assess possible implications for polarimetric

classification


Presentation Overview

• Introduce Project Study Area

• Show ellipsoidal and local incidence angle ranges

• Introduce statistical method for investigating scattering mechanisms

• Characterize impact of incidence angle on scattering mechanisms

• Analyze trends


Land Cover Classificationof Yellowstone

ylwstn_26903_10067

Aug 10, 2010


Ellipsoidal Incidence Angle

Ranges from 12 to 64 degrees

Incidence Angle Variability

70 degrees

0 degrees


Hillshade DEM



Local Incidence Angle


90 degrees

0 degrees


Segmentation of Local Incidence Angle



Reference DataUSGS NLCD 2006


Use PolSARpro and GIS to create a statistical characterization of

polarimetric scattering for individual land cover classes

Use to:

• Investigate the physics of scattering for specific classes

• Explore impact of varying the local incidence angle

Statistical Analysis of

Scattering Mechanisms

Surface

Double Bounce

Volume


3x3 Multilooked C3 VanZyl Decomposition Convert to GeoTIFF

POA compensation Compute Class PDFs

in GIS

Polarimetric Processing


Extracting Scattering

Strengths from Land Cover

GIS Procedure:

• Normalize the polarimetric decomposition components

(Surface, Double, Volume) for each resolution cell

• Determine Probability Distribution Function of Scattering

Strengths for each Land Cover Class


Extracting Scattering

Strengths from Land Cover

GIS Procedure:

• Normalize the polarimetric decomposition components

(Surface, Double, Volume) for each resolution cell

• Determine Probability Distribution Function of Scattering

Strength for each Land Cover Class

Surface

Double Bounce

Volume


VanZyl Decomposition

(all Incidence Angles)

Surface

Double Bounce

Volume


Pixel Count per Incidence Angle


Incidence Angle Analysis

Surface

Double Bounce

Volume



Surface

Double Bounce

Volume


Trend Analysis

Surface

Double Bounce

Volume


Class: Evergreen

Surface

Double Bounce

Volume


Class: Woody Wetlands

Surface

Double Bounce

Volume


Class: Shrub/Scrub

Surface

Double Bounce

Volume


Class: Herb/Grassland

Surface

Double Bounce

Volume


Class: Emergent Herb Wetlands

Surface

Double Bounce

Volume


Class: Barren Ground

Surface

Double Bounce

Volume


Comparison:

• Scattering power of surface scattering drops off as function of angle

• Corresponding growth of volume and double bounce

• Barren ground exhibits strong specular reflection effect

Comparison:

Barren Ground vs Evergreen Forest

Surface

Double Bounce

Volume

Surface

Double Bounce

Volume


Comparison:

Herb Wetlands vs Woody Wetlands

Comparison:

• Herb wetlands and woody wetlands differ in magnitude of surface

scattering

• Herb wetland exhibits rapid fall-off of surface scattering, similar to

barren ground

Surface

Double Bounce

Volume

Surface

Double Bounce

Volume


Comparison:

Herb/Grassland vs Shrub/Scrub

Comparison:

• Trends for Herb/Grassland and Shrub/Scrub are remarkably

similar making it hard to distinguish these two vegetation classes

Surface

Double Bounce

Volume

Surface

Double Bounce

Volume


Summary

• Introduced methodology for characterizing scattering mechanisms

using VanZyl decomposition

• VanZyl scattering mechanism vary strongly as a function of local

incidence angle for all classes

• Trend across classes included diminishing surface scattering and

increasing volume and double bounce scattering as incidence angle

increases

• This effect is most pronounced for smooth surfaced (e.g. barren

ground and emergent wetlands)


Questions?

Rick Guritz

[email protected]

(907) 474-7886

Photo Credit: Don Atwood

polarimetric implications of incidence angle variability for uavsar

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