On the Use of ALOS-PALSAR Mosaics to Study Ocean Surface Features of

Pakistan Coastal Region

Jibran Khan1 and Waqas A. Qazi2

1Lecturer, Dawood University of Engineering & Technology, Karachi

M.Phil. Scholar, ISPA, University of Karachi.

jibranliaquat@gmail.com

2Assistant Professor, Department of Space Science

Institute of Space Technology, Islamabad

http://grel.ist.edu.pk

International Conference on Space (ICS) – 2014, Islamabad

Contents

• Introduction

• Data

• Area of Interest

• Methodology

• Results

• Conclusions

Introduction

• Knowledge of ocean surface features is vital for coastal management applications

• Pakistan coastal region plays an important role in Asian monsoon and biological productivity

• Not many remote sensing studies describing physical oceanographic features of this region

Introduction

• Synthetic Aperture Radar (SAR) offers a unique solution to study ocean surface features due to:

all-weather observation capability (except rain)

high resolution

not affected by dust storms

Basic Mechanism of SAR Ocean Imaging (Bragg Scattering)

Illustration of Bragg Scattering; Where, λ r is the Radar wavelength, λB is the sea surface wavelength, θ is the local angle of incidence (Adapted from Martin, 2004)

The PALSAR Instrument • PALSAR is an active microwave SAR instrument that

uses L-band frequency to perform cloud-free observations

• PALSAR was onboard JAXA’s first Advanced Land Observation Satellite (ALOS-1)

ALOS – I Configuration (Source: JAXA)

Datasets Used

• Phased Array L-Band SAR (PALSAR) intensity mosaic data from 2010

– 50 m resolution

– Acquired from JAXA

• Moderate Resolution Imaging Spectrometer (MODIS) Sea Surface Temperature (SST) ocean products

– Day time SST Level 2 products from NASA

– 1 Km resolution

Area of Interest (AOI)

PALSAR HH Polarization Intensity Mosaic of Area of Interest © JAXA

Methodology

Identification of ocean surface features of PALSAR imagery

Validation of identified ocean features using MODIS data

Visual assessment of PALSAR Intensity Mosaic

Extraction of Acquisition Dates of PALSAR Intensity Mosaic

24th August 2010

Acquisition dates of 2010 PALSAR intensity mosaic i.e., 5th September 2010 (right), 1st May 2008 (center) and 24th August 2010 (left)

PALSAR intensity mosaic of 24th August 2010

Extraction of Acquisition Dates for PALSAR Mosaic Image

Front identification in 24th August 2010 PALSAR mosaic (left most part)

Identifying Ocean Surface Features in PALSAR Mosaic Imagery – SST Front

Validating SST Front using MODIS SST Products

MODIS True Color Images of respective dates showing cloud obscuration, which was a limitation in comparison process

MODIS Level-2 SST image (26th August 2010) of the study area where signature of front is clearly visible (left) Quality levels SST image of the same date and location (right) where SST Is found to be reliable (0 being most reliable and 4 being unacceptable SST)

Validating SST Front using MODIS SST Products

Location of SST front at approximately 20 Kilometers from the coast in PALSAR HH polarization intensity image of 26th August 2010

Validating SST Front using MODIS SST Products

Location of SST front at same location of approximately 20 Kilometers from the coast in MODIS Level-2 SST image of 26th August 2010

Validating SST Front using MODIS SST Products

Location of SST front at same location of approximately 20 Kilometers from the coast in both PALSAR HH polarization intensity image (top) and MODIS Level-2 SST image of 26th August 2010 (bottom)

Validating SST Front using MODIS SST Products

Identifying Ocean Surface Features in PALSAR Mosaic Imagery – Fresh Water Outflows

Identifying Ocean Surface Features in PALSAR Mosaic Imagery – Ships

Summarizing the Results

False color PALSAR intensity mosaic summarizing results of identified ocean surface features with better visualization

Conclusions

• Phased Array L-Band SAR intensity mosaicked image has been used to study ocean dynamics along Pakistan coastal region

• Fresh water outflows, SST front and some ships along Karachi coast have been identified

• Some other interesting ocean surface features were also identified that are to be explored further

Conclusions

• Study highlighted the immense potential of PALSAR to analyze ocean surface dynamical features

• This preliminary study would open news doors to further explore ocean dynamics in this important region utilizing SAR imagery

Questions / Comments?

Thank You!