Dr. Muhammad Shafique

NCE in Geology

INTRODUCTION TO REMOTE SENSING

Remote Sensing

Remote Sensing is:

The art and science of obtaining spatial information about an object or phenomenon without being in direct contact with the object (Jensen 2000).

The collection of information about Earth surfaces and phenomena using sensors not in physical contact with the surfaces and phenomena of interest.

Remote Sensing

Remote Sensing

History of Remote Sensing

The history of remote sensing began with the invention of photography. The term "photography" is derived from two Greek words meaning "light" (phos) and "writing" (graphien).

1858 - Gasper Felix Tournachon “Nadar" takes the first aerial photograph from a captive balloon from an altitude of 1,200 feet over Paris.

History of Remote Sensing

1860's - Aerial observations, and possible photography, for military purposes were acquired from balloons in the wars. Balloons were used to map forest in 1862.

History of Remote Sensing

1903 - The Bavarian Pigeon Corps uses pigeons to transmit messages and take aerial photos.

History of Remote Sensing

1914-1918 - World War I

1908 - First photos from an airplane

History of Remote Sensing

1914 - WWI provided a boost in the use of aerial photography,

but after the war, enthusiasm waned

History of Remote Sensing

1946 - First space photographs from V-2 rockets.

1954 - U-2 takes first flight.

History of Remote Sensing

1957 - Russia launches Sputnik-1, this was unexpected and encouraged the rest of the world for race of space exploration.

History of Remote Sensing

Late 1960's - Gemini and Apollo Space photography.

History of Remote Sensing

Energy Source or Illumination (A) Radiation and the Atmosphere (B) Interaction with the Target (C) Recording of Energy by the Sensor (D) Transmission, Reception, and Processing (E) Interpretation and Analysis (F) Application (G)

Source: Canadian Centre for Remote Sensing

Remote Sensing process components

1.ENERGY SOURCE (PASSIVE SYSTEM): sun, irradiance from earth’s materials; (ACTIVE SYSTEM):

irradiance from artificially-generated energy sources such as radar)

2.PLATFORMS (Vehicle to carry the sensor) (truck, aircraft, space shuttle, satellite, etc.) 3.SENSORS (Device to detect electro-magnetic radiation) (camera, scanner, etc) 4.DETECTORS (To convert electro-magnetic radiation into recorded signals) (film, silicon detectors, etc) 5.PROCESSING (Handling signal data) ( photographic, digital) 6.INSTITUTIONALISATION (Organization for execution at all stages of remote-sensing technology: international and national organizations, centers, universities, etc

Remote Sensing process components

Visual

Quantitative

(i)Users

(e) Sensing systems (f)Data products (g) Interpretation

procedures

(h) Information

products

Reference

data

Pictorial

Numerical

DATA ACQUISITION DATA ANALYSIS

( a) Sources of energy

( c)Earth’s surface features

(d) Re-transmission

through the atmosphere

(b) Propagation

through the

atmosphere

Remote Sensing process components

A technology used for obtaining information about a target through the analysis of data acquired from the target at a distance.

Applications

Remote Sensing process components

Types of Remote Sensing

There are two main types of Remote sensing: a. Passive Remote Sensing: Makes use of sensors that detect the reflected or emitted electro-magnetic radiation from natural sources. b. Active remote Sensing: Makes use of sensors that detect reflected responses from objects that are irradiated from artificially-generated energy sources, such as radar.

Remote sensing

Information extracted from remote sensing images depend on type of energy the remote sensing system detect

Energy detected by remote sensing system is electromagnetic energy

All objects with temperature above absolute zero temperature continuously emit electromagnetic radiation

Where: absolute zero on Kelvin temp scale is equivalent to -273⁰ C and -459.7⁰ F.

(E) Electric Field, (M) Magnetic Field, (C) Speed of Light

Electromagnetic radiation consists of an electrical field (E) which varies in magnitude in a direction perpendicular to the direction in which the radiation is traveling, and a magnetic field (M) oriented at right angles to the electrical field. Both these fields travel at the speed of light (c).

Electromagnetic radiation

Electromagnetic waves are produced by the motion of electrically charged particles. These waves are also called "electromagnetic radiation" because they radiate from the electrically charged particles. They travel through empty space as well as through air and other substances.

Electromagnetic radiation

Electromagnetic radiation

Wave Terminology

Wavelength - distance between two like points on the wave

Amplitude - the height of the wave compared to undisturbed state

Period - the amount of time required for one wavelength to pass

Frequency - the number of waves passing in a given amount of time

Electromagnetic Spectrum

Electromagnetic Spectrum

Resolution

Resolution determine the ability of remote sensing data to distinguishing between different objects.

Types of resolution

Spatial resolution is a measure of the smallest object that can be resolved by the sensor, or the linear dimension on the ground represented by each pixel or grid cell in the image

Spectral resolution describes the specific wavelengths that the sensor can record within the electromagnetic spectrum.

Temporal resolution is a description of how often a sensor can obtain imagery of a particular area of interest. For example, the Landsat satellite revisits an area every 16 days as it orbits the Earth, while the SPOT satellite can image an area every 1 to 4 days.

Radiometric resolution refers to the number of possible brightness values in each band of data and is determined by the number of bits into which the recorded energy is divided. In 8-bit data, the brightness values can range from 0 to 255 for each pixel (256 total possible values). In 7-bit data, the values range from 0 to 127, or half as many possible values.

Spatial resolution

I m resolution 2 m resolution 5 m resolution

10 m resolution 20 m resolution 30 m resolution

Spatial resolution refer to smallest feature differentiable on an image

ALI 30m

9 bands

Hyperion 30m

242 bands

TM 30m

6 bands

ASTER

15m VNIR, 30m SWIR

9 bands

MIVIS 8m

102 bands

IKONOS 4m

4 bands

Characteristics of different images

100 meter resolution

30 meter resolution

5 meter resolution

Spectral Resolution

Number and width of spectral bands recorded by an image

Only one band covering BGR visible range

called panchromatic

Spectral Resolution

Spectral Resolution

8-bit (0 - 255)

9-bit (0 - 511)

10-bit (0 - 1023)

0

0

0

The sensitivity of remote sensing detectors to differences in signal strength or brightness level it detects. Higher sensitivity finer the R.R. Measured in levels of data storage units

Radiometric Resolution

Radiometric resolution

8-bit quantization (256 levels) 6-bit quantization (64 levels)

4-bit quantization (16 levels) 3-bit quantization (8 levels)

2-bit quantization (4 levels) 1-bit quantization (2 levels)

Temporal Resolution

Frequency of image acquisition,

Or revisit time

Application of Temporal images

Nowshera city, 2010 Before flood After flood

Different Types of Satellite Images

LAND SAT

SPOT

KOMET

IKONOS

QUICK BIRD

LANDSAT (USA)

Bands:7

Resolution:30m

Area Covered: 185x 185 Km

SPOT (France)

Band : 3

Resolution:

Pan:10 m

XS: 20 m

Area Covered:

60 x 60 m

Kometa (Russia)

Bands: Only Panchromatic

Resolution: 2 m

Area Covered:

40 x 40 Km

IKONOS (USA)

Band : 3

Resolution:

Pan:1 m

MS: 4 m

Area Covered:

11 x 11 Km

Quick Bird (USA)

Band : 3

Resolution:

Pan:0.61 m

MS: 2.44 m

Area Covered:

13.5x13.5 m

Integration of Remote sensing and GIS

Integration of Remote sensing and GIS

Remote sensing provides a regional view It enable us to observe & measure the causes & effects of climate &

environmental changes (both natural & human-induced)

Remote sensing provides repetitive geo-referenced looks at the same area

Remote sensors “see” over a broader portion of the spectrum than the human eye

Sensors can focus in on a very specific bandwidth in an image

They can also look at a number of bandwidths simultaneously

Some remote sensors operate in all seasons, at night, and in bad weather

Advantages of Remote sensing