7/29/2019 RS Education1

1/16

RS Education

Part 1

7/29/2019 RS Education1

2/16

Definition

Remote Sensing is thescience and art of acquiringinformation about the Earthssurface without actually beingin contact with it.

This is done by sensing andrecording reflected or emitted

energy and processing,analyzing, and applying thatinformation.

7/29/2019 RS Education1

3/16

The Remote Sensing Process

A) Energy Source or Illumination

B) Radiation And The Atmosphere

C) Interaction With the Target

D) Recording of Energy by Sensor

E) Transmission, Reception &Processing

F) Interpretation and Analysis

G) Application

7/29/2019 RS Education1

4/16

A) Electromagnetic Radiation

Source of Energy

Electrical Field and Magnetic field of EM Radiation

Frequency and Wavelength of EM Radiation

The shorter the Wavelength

The greater the Frequency

7/29/2019 RS Education1

5/16

Electromagnetic Spectrum

7/29/2019 RS Education1

6/16

B) Radiation and the Atmosphere

Particles and gases in the Atmosphere can affect the incoming lightand radiation. These affects are scattering andAbsorption.

Rayleigh Scattering

Mie Scattering nonselective Scattering Blue+Green+Red=White

Why the Sky is Blue during day and Red at sunset & sunrise?

The Shorter the Wavelength, The Greater the Scattering

Why the clouds are present in optical images &

absent in Radar images?

7/29/2019 RS Education1

7/16

B) Radiation and the AtmosphereAbsorption

Ozone, Carbon dioxide, and Water Vapor are main radiationabsorbers.

Ozone absorbs the ultraviolet radiation from the sun.

Carbon dioxide also referred to as greenhouse gas which absorbs

radiation in the far IR (area associated with thermal heating).

Water Vapor absorbs long wave IR & shortwave microwaveradiation (between 22m and 1m).

Atmospheric Windows

Most of the sensors dont work in UV and Blue portions because ofhigh scattering and absorption.

Scattering of Blue is 4 times more than Red

7/29/2019 RS Education1

8/16

C) Interaction with the Target

Absorption, Transmission and Reflection

Why do we see Vegetables Green?

Specular and Diffuse Surfaces

Spectral Reflectance Curve

Affects by : Target Type, Time (e.g. Greenness of Leaves),

Location

By comparing the response patterns of different features we may beable to distinguish between them (but not by only 1 wavelength).

7/29/2019 RS Education1

9/16

C) Interaction with the Target

So the Spectral Reflectance can be used to distinguish objects onthe images.

Indices

Normalized Difference Vegetation Index (NDVI)

IR RNDVI

IR R

7/29/2019 RS Education1

10/16

D) Recording of Energy by Sensor

Until now we have spoken about 3 first components ofRemote Sensing Process called: Energy source, interactionwith atmosphere, interaction with surface.

Ground Based SensorsAir Based Sensor (aircraft, occasionally Helicopters, )

Space Based Sensors (Satellites, )

7/29/2019 RS Education1

11/16

Satellite Characteristics: orbits & Swaths

The Path followed by a satellite is referred to as its Orbit.

Geostationary Orbits (altitude of 36000km, Stationary, Weather & communication)

Sun-Synchronous Orbits

near-polar orbits

cover each area of the world at a constant local time of day

Cause consistent illumination conditions

7/29/2019 RS Education1

12/16

Satellite Characteristics: orbits & Swaths

Sun-Synchronous Orbits

ascending and descending passes

the ascending pass is most likely on the shadowed side of theEarth while the descending pass is on the sunlit side

Sensors recording reflected solar energy only image thesurface on a descending pass, when solar illumination isavailable.

Active sensors which provide their own illumination or passivesensors that record emitted (e.g. thermal) radiation can alsoimage the surface on ascending passes.

Swath (Earth Rotation & new area with each consecutive

pass,

Different Overlap in adjacent swaths)

7/29/2019 RS Education1

13/16

Some Terms

Aerial Images Space Images

Sensor

Platform (Satellite, airplane, )

Each Satellite can carry some sensors Imaging Band or Channel

Passive Sensors (Optical sensors, )

Active Sensors (Lasers, SAR, )

Analog Photographs

Digital Images

Nadir

Pixel

Digital Number (DN)

7/29/2019 RS Education1

14/16

Digital Images

As we said before, our eye is only able to see a narrow electromagnetic visibleBand, while sensors can provide data in a very larger extent of EM spectrum.

By showing various wavelength bands in different main colors (Blue, Green, Red),We can see various color images:

Black and White Images

True Color Composite Images

False Color Composite Images

7/29/2019 RS Education1

15/16

7/29/2019 RS Education1

16/16

Work on Erdas Software

Familiarizing with Erdas Software Interface, showingImages, speaking about Image Formats

Showing imaging Bands, black and White image views,

True Color and False Color view

Viewing image digital numbers

Displaying of spectral reflectance curve for various areas of

the images

Notice to How to Use Erdas Help