mdp3-remote sensing concepts

8/7/2019 MDP3-Remote Sensing Concepts

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Remote Sensing•Remote Sensing is the science of acquiring information about

the earth surface without actually being in contact with it.

•The method is commonly restricted to employ

electromagnetic energy (such as light, heat and radio waves)

as the means of detecting and measuring targets.• •Remote Sensing is an advanced form of Surveying in which

land surveying has been replaced by aerial photographs &

satellite images.

•Applications whether it is geographical, geological,

oceanographic or cartographic, Remote Sensing is the

essential tool for all application areas.



Earth Surface

Sources

of Energy Sensing

Systems

TransmissionAbsorption

Emission

Scattering

Reflection

Remote Sensing Basics

Electromagnetic Energy

Electromagnetic Energy refers to all energy that moveswith the velocity of light in a harmonic wave pattern.



V

isible

Light

n

earinf ra

red

m

idinfr a

red

thermal

infrared

U

l t r a

v i o l e t (

U V

)

m

icrowa

ve

TVand

radio

X

r a y

s

γ

r a y

s

b l u

e

g r e e n

r e

d UV near

infrared

110-110-210-310-410-510-6 10410310210 107106105

wavelength (µ m) wavelength (µ m)

0.4 0.5 0.6 0.7 µ m

Electromagnetic Spectrum

Emissions are recorded in various wavelengths of visible region.



Based on source of energy, Remote Sensing can be broadly

divided in two categories.

(i) Passive Remote Sensing(ii) Active Remote Sensing

When remote sensing instruments both generate and detect their

own source of radiation, the process is called Active remotesensing. i.e.Aerial Photography, Microwave remote sensing etc.

In case of Passive remote sensing sensors detect and recordvariation of solar or terrestrial origin in the visible, infra-red and

microwave wave bands.



Aerial Photography is the original form of remote sensing

and remains the most widely used methods. Aerial

Photography analyses have played major roles in discovery

of many oil and mineral deposits around the world.

Aerial photographs are acquired with the help of specially

designed cameras which are mounted on the aircraft. These

aircrafts fly over the ground and record the photographs of

the area.

Based on technology used, Remote Sensing can be broadly

divided in two categories.

(i) Aerial Photography(ii) Satellite Remote Sensing



In case of Satellite remote sensing, sensors are mounted on

the satellites which record the reflectance value from various

objects and forms a digital image. The satellites revolvearound the earth at several hundred kilometers from the

earth’s surface. This can be treated a form of active remote

sensing.



Aerial Photograph of Tokyo (Japan)



Portion of Ranchi Town



Sensor

IFOV

FOV



0 2 2 2 15

8 23 2 12 120

0 0 3 56 56

32 255 61 45 21

12 61 213 0 31

1 0 1 2 2 62 15

18 23 13 12 210

0 0 3 56 56

32 255 1 61 45 21

42 61 21 0 31

No. of Pixels ->

NoofLines->

Red Band

12

4

Sensors

Satellite

Green Band

3

21 65 2 62 15

18 23 13 12 210

70 20 53 56 5632 251 161 45 21

42 151 21 10 31

Blue Band3 32 52 10 2 15

18 13 100 12 120

50 30 13 156 56

42 205 161 45 21

19 61 13 0 37

Satellite Image

IR Band



Each scan line of a remotely sensed image is

a digital or numerical record of radiance

measurements made at regular intervalalong the line. A set of consecutive scan lines

thus forms an image.

Image data thus numerical in nature can be

processed with the help of computers to

derive the meaningful information.



Geo-Stationary Satellite

The satellite’s orbital velocity is just sufficient to

keep pace with the rotation of earth.

Sun-Synchronous SatelliteThey acquire the image of specific portion of the

earth at a fixed local sun time.



Satellite Data Format : BIP (Band Interleaved by Pixel)

BIL (Band Interleaved by Line)

BSQ (Band Sequential)

Histogram : A graph between the Grey-Values (intensity values)

& corresponding frequencies

Signal : Actual radiations measured in the image.

Noise : Unwanted signals recorded in the image.



Raster & Vector Data



Resolution

Spatial : Smallest possible feature that can be detected. This

area on the ground is called the resolution cell anddetermines a sensor’s maximum spatial resolution.

IRS 1C - 23.5 X 23.5 (LISS III)

5.88 X 5.88 (PAN)

Spectral : Individual images have been separately recorded in

discrete spectral bands. The term spectral resolution

refer to the width of these spectral band

Radiometric: Refers to the number of digital level used to express

the data collected by the sensors.

Temporal : The revisit period of a satellite sensor.



Multi-spectral Scanning



Panchromatic Scanning



Satellite Image of Patna as viewed By IKONOS



Satellite Image of Patna Airport as viewed By IKONOS



Digital Image Processing

• Image Pre-processing

• Image Enhancements

•Image Classification



IMAGE PRE-PROCESSING

Remote Sensing image, acquired by satellite/aircraft

have various geometric distortions.

These errors may be due to :

• the curvature and rotation of the earth• the motion of the scanning system• the motion and (in)stability of the platform



Pre-processing operation :

•Radiometric Correction [ For Sensor & Platform

specific errors]

•systematic striping or banding and dropped lines.

•Geometric Correction/Registration [ for Geo-metric

distortion of data ].



IMAGE ENHANCEMENT

Used to make it easier for visual interpretation and analysis of

imagery.

Contrast Enhancement : The visual quality of an image can be

improved if the contrast (intensity values) between the darkest and

the lightest parts of image is enhanced.

Raw Image, having contrast values between 17-80, If we map these

intensity values on 0-255 scale , the visual quality of image will

enhanced.



Raw Satellite Image

Enhanced Satellite Image



Spatial Filtering :

Spatial filters are designed to highlight or suppress

specific features in an image based on their spatialfrequency. There are two main types of filtering

techniques suited to different types of applications.

1. Low Pass Filtering or Noise Removal Filtering 2. High Pass Filtering or Edge Detection Filtering



Low Pass Filtering or Noise Removal Filtering

A Low-pass filter is designed to remove the noise/lowfrequency components from the image. These filters

are also called smoothing filters. These are :

• Mean• Mode• Median



High Pass Filtering or Edge Detection

FilteringA High-pass filter is designed to suppress high frequency

components from the image. Directional, or edge detection filtersare designed to highlight linear features, such as roads,fields or

water body boundaries.

Some of these filters are :• Laplacian• Robert• Kirsch• Sobel

• Prewitt• Highboost



IMAGE CLASSIFICATION

Image classification is used to classify the satellite imagery into

actual land classes/categories. Classification may be very useful for the identification of different kind of crops, different forest types or

tree species, different geologic units or rock type, water spread, etc.

Classification is divided into two broad categories, these are :-

Supervised classification : In this method the analyst provide/

identify representative samples (also referred to as training sample

area) of different surface cover type of interest. Based on the

training sample area the processing is done over the imagery to getthe classified image.



Unsupervised Classification :

In this method the programs, called clustering algorithms,are used to determine the natural (statistical) grouping or

structures in the data. Usually in this process the analyst

specify only the desired number of classes. In addition the

analyst may specify parameters related to the separation

distance among the clusters and the variation within each

cluster. If the image geometry is transformed so as to

match a known coordinate system, the resultant classified

image is in form of a thematic map and is suitable for

export as an input to a digital Geographical informationsystem (GIS).



Spatial Data Infrastructure for

Multi-layer GIS Planning



11. Drainage

12. Agriculture

13. Forest

14. Soil

15. Landuse/Landcover 16. Wasteland

17. Wetland

18. Geology

19. Hydrogeomorphology/Geology

20. Slope,Aspect and Relief

21. DEM

22. Watershed23. Ground Water

Extraction of thematic layers:

The core objective of this Planning Commission project is to develop 23

basic thematic layers at 1:50,000 scale for the entire country for planning process,

management of resources.

These layers are as follows:

1. Administrative Boundaries

2. Village Locations and boundaries

3. Contours

4. Elevation Height

5. Misc. Point data sets with attributes

6. Major Towns /Cities ,etc

7. Settlements

8. Railway Lines

9. Road

10. Water Bodies



Satellite data is an important source of informationabout land cover and land use. The layers extracted from it either form an end layer or an input layer for further analysis

into GIS. The data from IRS series satellites are supplied by NRSA, Hyderabad. Following datasets from different types of sensors been procured for this project:

AWIFS - Covering entire country LISS-III - Covering entire country PAN - Covering entire country Quickbird - Selective areas, covering the Distt. Hdqrs.

Cartosat-1 – Selective areas - few hilly terrains



Sensor: AWIFS

SpatialResolution: 50m

Spectral Bands(in microns) :0.52-0.590.62-0.680.77-0.861.55 - 1.70

Swath: 125 *125 K

Total All Indiatiles: 394



Sensor: LISS-III

Spatial Resolution:23.5m

Swath: 125 * 125Km

Total All India tiles:394 @ Rs. 22500

Spectral Bands:0.52 - 0.59

0.62 - 0.68

0.77 - 0.86

1.55 - 1.70



Sensor: Pan


Swath: 31.25 *

31.25 Km Total All India tiles:3491 @ Rs.12300

Spectral Band:0.50 - 0.75



Sensor: Cartosat

20-24 Distt. HQ of hilly

terrain


Spectral Band:0.5 – 0.85



Infrastructure layers for Punjab



Guidelines for Data ordering

To obtain satellite data, users have to specify their area of interest.

This may be:a city a district

a stateany contiguous area

This can also be specified in terms of:latitude / longitude of corners of a polygonpath / row number (obtained from a referencing scheme map)map sheet number (as per Survey of India SOI nomenclature)

For more information on the procedure to procure, visit the link:http://www.nrsa.gov.in/products/area_coverage.html

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