Application of Remote Sensing in the

Monitoring of Marine pollution

By

Atif Shahzad

Institute of Environmental Studies

University of Karachi

Remote Sensing

"Remote sensing is the science

(and to some extent, art) of

acquiring information about the

Earth's surface without actually

being in contact with it. This is

done by sensing and recording

reflected or emitted energy and

processing, analyzing, and applying

that information.’’

The term, “remote sensing,” was

coined by Evelyn L. Pruitt (U.S.

Office of Naval Research) in 1960.

Evelyn Pruitt

Energy Source

The Sun

The first requirement for remote sensing is to have an energy source which

illuminates or provides electromagnetic energy to the target of interest.

From Lillesand & Kiefer, 2001

Electromagnetic Radiations

Long wave

Radio wave, Micro wave, IR

Visible

Red-VioletShort wave

UV, X-ray

The Electromagnetic Spectrum

Long wave

Visible

Short wave

Atmospheric interaction

As the energy travels from its

source to the target, it will

come in contact with the

atmosphere it passes through.

This interaction may take

place a second time as the

energy travels back from the

target to the sensor.

There are three types of

interactions.

Reflection

Absorption

Scattering

Atmospheric interaction

Platform

Platform is the place where sensors

are mounted on.

1. Balloon

2. Kite

3. Pigeon

4. Airplane

5. Satellite

Platforms

Balloon photography, 1858The first known aerial photograph is obtained by aeronaut Gaspard Felix

Tournachon, also known as Nadar, was a famous French photographer and

balloonist whose goal was to make land surveys from aerial photographs.

NADAR

Nadar’s 1868 photo of Paris

Platforms

Kite Photography, 1890Arthur Batut pioneered the development of kite aerial photography and took a

photograph of Labruguiere, France in 1890.

Labruguiere, France

Arthur Batut

One of Lawrence's 1906 photographs of San Francisco.

Platforms

In 1906, George R. Lawrence took oblique aerial pictures of San Francisco after the

earthquake and fires

Platforms

Pigeons Photography, 1903

In 1903, Julius Neubranner, photography enthusiast, designed and patented a breast-

mounted aerial camera for carrier pigeons

Platforms

Aerial Photography, 1909The first photographs from an aircraft were taken by L. P. Bonvillain, a passenger ofWilbur Wright, during a demonstration flight in France.

Aerial photographer during World War I, and a French air field

Satellite Imagery, 19721972 - Launch of ERTS-1, the first Earth

Resources Technology Satellite (later

renamed Landsat 1). Carried return beam

vidicon (RBV) and multispectral scanner

(MSS).

Platforms

Brazil Deforestation

Landsat mss June, 19 1975 vs

Landsat TM August 19, 1986Landsat 1

Sensor

After the energy has been reflected by, or emitted

from the target, we require a sensor (remote - not

in contact with the target) to collect and record

the electromagnetic radiation.

The sensor acquires several images (bands) at

once, each recording a specific color or range of

colors. When viewed, each individual band looks

like a black and white photograph

Types of Sensors

There are two types of sensors with respect to

illumination source.

Passive sensors measure natural radiation emitted by the

target material or/and radiation energy from other sources

reflected from the target.

Active sensors transmit their own signal and measure the

energy that is reflected (or scattered back) from the target

material.

Today, we will be focusing on passive remote sensing!

Passive Sensor (Landsat TM)

Karachi

A satellite view of Karachi from Landsat a passive remote sensing satellite

Active Sensor (Radarsat)

Karachi

Interaction with the feature

When electro-magnetic energy is incident on any given earth

surface feature, three fundamental energy interactions with the

feature are possible depending on the properties of both the

target and the radiation.

Transmission

Reflection

Absorption

Interaction with the feature

Basic interactions between electromagnetic energy and an earth

surface feature

The incident energy on an earth surface feature is a function of reflected, transmitted and

absorbed energy.

From Avery &

Berlin, 1977

Reflectance from a leafAn earth surface feature behaves differently against different spectral bands. As we

can see that a leaf absorbs incident energy in blue and red bands while it reflect

energy in green and near infra red bands.

Spectral Reflectance Curve

Spectral reflectance curve reveals that vegetation (leaves) has maximum reflectance in

NIR than green band.

Reflectance in different bands

Applications

On the basis of spectral reflectance

and field measurements we can

find parameters that are important

in the monitoring of plant diversity

1. Chlorophyll (a & b)

2. Vegetation density (NDVI)

3. Species Richness (No. of

Species)

Chlorophyll-a

This paper focused on developing and applying remote sensing

algorithms to determine the chlorophyll-a content of mesotrophic to

highly eutrophic lake waters, using Lake Taihu, China as a case study.

Statistical techniques have been the most commonly used approach to

derive a correlation between spectral data and chlorophyll

concentration values (Zhou yi et al., 2004). Such techniques were also

adopted in this study.

1. Weiqi Zhou, Shixin Wang, Yi Zhou. Determination of Chlorophyll a Content of the

Lake Taihu, China using Landsat-5 TM data. Institute of Remote Sensing Applications,

Chinese Academy of Sciences P O Box, 9718, Beijing 100101, P R. China.

2. Zhou yi, Zhou Weiqi, Wang shixin et al. Applications of Remote Sensing Techniques to

Inland Water Quality Monitoring. Advances in Water Science, 2004, 15(3), 312-317. (In

Chinese)

Field measurement

Water was sampled at 0.5m depths using a bottle and was laterfiltered and stored in liquid nitrogen to break the algae cells.Chlorophyll concentrations were retrieved from filtered waterusing the hot ethanol method, which use 90% hot ethanol as thechlorophyll-a extraction agent (Chen and Gao, 2000). 25 chl-aconcentration measurements were collected on October 27th and28th, 2003, which were used as the dependent variable in theregression analysis with corresponding satellite-derived watersurface reflectance. The values of chl-a concentration variedfrom 2.2 mgm-3 to 230.59 mgm-3.

Chen yuwei, Gao xiyun. Comparison of Two Methods for Phytoplankton Chlorophyll-a

Concentration Measurement. Journal of Lake Sciences, 2000, 12(2): 186-188. (In Chinese)

Numerical modelBased on the correlation analysis between chl-a and various

bands and bands combinations, the multiple regressions were

performed using the 22 chl-a concentration values and selected

bands combinations. Closeness of fit (r2 values) and mean Std.

Error of the Estimate (SEE) were used to assess the regression

models. A four-coefficient regression model using TM4/TM3

ratio and TM1, TM2 was a reliable predicator of chl-a (r2 =

0.837). The equation of this model is:

Where R1, R2 were the reflectance of TM1 and TM2; R43 was the reflectance ratio of

TM4 to TM3.

Remote Sensing Analysis

Map of chl-a concentrations (in mgm-3), by applying numerical

model to Landsat TM reflectance data from October 28th, 2003.