Remote Sensing

Platforms with Sensor on board 

Illumination 

GMS 

(Geostationary Satellite) 

LANDSAT, MOS, 

SPOT 

SPACE SHUTTLE 

atmosphere 

HIGH ALTITUDE 

JETPLANE 

emission 

reflection 

LOW&MIDDLE 

ALTITUDE AIRPLANE 

GROUND TRUTH 

object 

Remote Sensing - Introduction

Contents - Introduction to RS 

• Principles of Remote Sensing 

– electromagnetic radiation 

– atmospheric interaction 

– surface reflection 

• Remote Sensing systems 

– Platforms 

– Sensors 

– Resolution: spatial, spectral, temporal 

• Applications of Remote Sensing 


Definition of Remote Sensing 

Remote Sensing is a method to acquire 

information about material objects, areas, or 

phenomenon through the analysis of data 

acquired by a device from measurements made 

at a distance, without coming into physical 

contact with the objects, areas, or phenomena 

under investigation. 


Why Remote Sensing 





• To recognize macro-patterns which may not 

be visible from ground 

• To gain an OVERVIEW of an area 

• To gather information on large areas in short 

time 

• To gather information cost-effectively 

• To gather information on inaccessible places 

• To replace conventional sources of 

information (topo sheets, census data etc.) 


What is Remote Sensing 

We acquire much information about our surrounding through the 

senses of sight and hearing which do not require close contact 

between the sensing organs and the external objects. In another word, 

we are performing Remote Sensing all the time. 

Generally, Remote sensing refers to the 

activities of recording/ observing/ 

perceiving (sensing) objects or events at 

far away (remote) places. 

Remote Sensing - Introduction 

Earth from Space

How does Remote Sensing Work 

Electro-magnetic radiation which is reflected or emitted from an object 

is the usual source of remote sensing data. A device to detect the 

electro-magnetic radiation reflected or emitted from an object is called a 

"remote sensor" or "sensor". Cameras or scanners are examples of 

remote sensors. A vehicle to carry the sensor is called a "platform". 

Aircraft or satellites are used as platforms. 

The characteristics of an object 

can be determined, using 

reflected or emitted electromagnetic 

radiation, from the 

object. Each object has a unique 

and different characteristics of 

reflection or emission if the type 

of object or the environmental 

condition is different. . 


Principles of RS: EMR 

• The definition of RS implies the use of 

medium which carries the information from 

the object to the sensor 

• Usually, electro-magnetic radiation (EMR) is 

being used as medium 

• In passive RS, the radiation emitted by some 

other source is being used 

• In active RS, the radiation is being emitted by 

the system itself 


Electro-Magnetic Radiation (EMR) / 2 

electric field 

magnetic field 

travelling direction 

λ (wave length) 


The Electro-Magnetic Spectrum 

0.3 (cm) 1 3 10 30 100 

Microwave bands W V O Ka K Ku X C S L P 

Wavelength: 

Microwaves 

0.1nm 10nm 1µm 100µm 10mm 1m 100m 10km 

γ -ray X-ray UV Vis. Infrared EHF SHF UHF VHF MF LF VLF 

Radio waves 

Ultra Violet 

v 

I 

o 

l 

e 

t 

Visible Light 

b 

l 

u 

e 

g 

r 

e 

e 

n 

y 

e 

l 

l 

o 

w 

o 

r 

a 

n 

g 

e 

r 

e 

d 

Near Infra-red 

Short 

Wave 

Infra-red 

Intermediate 

Infra-red 

Thermal 

Infra-red 

wavelength (µm) 0.4 0.6 0.8 1 5 7 10 


Characteristics of spectral regions 

Region Wavelength Remarks 

Gamma Ray 30 cm Longest wavelength portion of the electro-magnetic spectrum. Some 

classified radar with very long wavelength operate in this region. 


• Makes use of sensors that detect the reflected or 

emitted electro-magnetic radiation from natural 

sources, most notably the sun. 

• Due to its surface temperature of 5800K, the sun 

emits most of its energy in the visible part of the 

spectrum. 

• The earth with a surface temperature of 300K emits 

most of its energy in the thermal part of the 

spectrum. 


Spectral emission, atmospheric 

transmittance and sensor sensitivity 

Figure (3a) 

Energy Source 

Figure (3b) 

Atmospheric 

Transmittance 

Thermal Scanners 

Figure (3c) 

Common Remote 

Sensing Systems 


Atmospheric Transmittance 


Interaction between EMR and surfaces 


Spectral Reflectance Curves 


Vegetation reflectance curves 

Chlorophyll 

absorption 

Water 

absorption 


Mineral Reflectance curves 


Remote Sensing Systems 

DATA ACQUISITION 

DATA ANALYSIS 

Reference 

data 

Pictorial 

Visual 

Numerical 

Quantitative 

Users 

Sources of 

energy 

Propagation 

through 

atmosphere 

Sensor systems Data products Interpretation 

procedures 

Re-transmission 

through atmosphere 

Information 

products 

Reflection on surface features 


Platforms 

Platform Altitude Observation Remarks 

geostationary satellite 36,000km fixed point observation GMS 

circular orbit satellite 

(earth observation) 

500km - 

1,000km 

regular observation 

LANDSAT, SPOT, 

MOS, etc 

space shuttle 240km - 350km irregular observations 

radio - sound 100m - 100km various investigations 

(meteorological, etc) 

high altitude jet-plane 10km -12km reconnaissance, wide area 

investigations 

low or mid altitude plane 500m - 8,000m various aero investigation surveys 

helicopter 100m- 2,000m various aero investigation surveys 

radio-controlled plane below 500m various aero investigation surveys aeroplane, 

hang-plane 50 - 500m various aero investigation surveys hangglider 

hang-balloon 800m - various investigations 

cable 10 - 40m archaeological investigations 

crane car 5 - 50m close range surveys 

ground measurement 

car 

0 - 30m ground truth cherry picker 


Earth Observation Satellite Orbits 

GROUND TRACK 

ALTITUDE = 705 KM 

(Nominal) 

INCLINATION = 98.2 O 

Equator crossing: 9:45am 

(Local time) 

DIRECTION OF TRAVEL 

ORBIT PERIOD = 98.9 MINUTES 


Earth Observation Satellite Orbits / 2 


Sensors 

A sensor or ‘remote sensor’ is a device 

to detect the electro-magnetic radiation 

reflected or emitted from an object. 

Cameras or scanners are examples of 

remote sensing-sensors. 


Sensors: Solid State Scanners 


Sensors: Opto-Mechanical Scanner 


Characteristics of RS systems: Resolution 

In general, resolution is defined as the ability of an entire 

remote-sensing system, including lens, antennae, 

display, exposure, processing, and other factors, to 

render a sharply-defined image. Resolution of a remotesensing 

system is of different types. 

(1) Spectral Resolution 

(2) Radiometric Resolution 

(3) Spatial Resolution 

(4) Temporal Resolution 


Spectral Resolution 

Detectors 

Incoming light 

(mix of different 

wavelengths) 

Prism or 

Spectrometer 


Spectral Resolution / 2 

coarse spectral resolution: only 1 value, 

same for soil and turbid water 

finer spectral resolution: 3 values, 

each is different for soil / water 


Spectral resolution of some RS systems 

0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 2.10 3.10 4.20 6.20 8.20 10.20 12.20 

SPOT Pan SPOT XS Landsat TM 

NOAA AVHRR IRS LISS IRS WiFS 

ADEOS AVNIR 


Spectral Band Range (µm) used in Thematic Mapper (TM) onboard 

Landsat's 4 and 5 sensor system and their potential application 

Band Band Range 

Number (µm) 

Potential applications 

1 0.45 to 0.52 coastal water mapping; soil/vegetation differentiation; 

deciduous/coniferous differentiation (sensitive to chlorophyll 

concentration); etc. 

2 0.52 to 0.62 green reflectance by healthy vegetation; etc. 

3 0.63 to 0.69 chlorophyll absorption for plant species differentiation; 

4 0.78 to 0.90 bio-mass surveys; water body delineation; 

5 1.55 to 1.75 vegetation moisture measurement; snow/cloud differentiation; 

6 10.4 to 12.5 plant heat stress management; other thermal mapping; soil moisture 

discrimination; 

7 2.08 to 2.35 hydrothermal mapping; discrimination of mineral and rock types; 


Spectral Band Range (µm) used in Advance Very High Resolution Radiometer 

(AVHRR) sensor onboard NOAA Satellite system and their potential application. 

CHANNEL WAVE LENGTH) USES 

NUMBER 

(µm) 

CHANNEL 1 0.58 - 0.68 cloud delineation, weather snow and ice mapping and monitoring, etc. 

CHANNEL 2 0.73 - 1.1 surface water delineation, vegetation and agriculture assessment, 

range surveys, etc. 

CHANNEL 3 3.53- 3.93 land/water distinction, sea surface temperature, hot spot detection 

(forest fires and volcanic activity),etc. 

CHANNEL 4 10.3 - 11.3 day/night cloud mapping, sea and land surface temperature, soil 

moisture, volcanic eruption, etc. 

CHANNEL 5 11.5 12.5 sea surface temperature measurement, soil moisture, weather, etc. 


Multispectral images: Landsat TM 

TM6 (10.4 - 

12.5) 



Spatial resolution / 2 

Landsat MSS (80m) 

SPOT XS (20m) 

IRS Pan (6m) 

KVR (2m) 

SPOT Pan (10m) Landsat TM (30m) IRS WiFS (188m) NOAA AVHRR (1.1km) 


Spatial Resolution 

SATELLITE 

SYSTEM 

SOME 

OPTICAL SENSOR 

SYSTEM 

LANDSAT 4/5 

MSS 

LANDSAT 4/5 

TM 

SPOT 

XS 

NOAA 

AVHRR 

MOS 

MESSR 

JERS 

OPS 

VINR 

and 

SWIR 

ADEOS 

AVNIR 

IRS-1C 

LISS-III 

IRS-1C 

WiFS 

Spatial Resolution 80 m 30 m 20 m 1.1 km (LAC) 50 m 18 m X 24 

m 

Off-nadir viewing 

SPOT PAN 

JERS 

(side-look) 

(10m 

OPS 

capability for the 

resolution) 

VINR 

(PAN) 

0.51- 0.73 µm 

(18m X 

Panchromatic 

3 days revisit 

24m) 

mode for stereo 

capability 

Bands 3 & 

image data 

4 

acquisition) 

0.76 - 0.86 

µm 

16 m 24 m 188 m (200 

m) 

ADEOS IRS-1C PAN 

AVNIR (6 m 

PAN resolution) 

(8 m (70 km swath 

Resolution) width) 

0.52 - 0.50 - 0.70 µm 

0.72 µm (6-bit) 


Spatial resolution: TM and SPOT Pan 


Temporal resolution 

SATELLITE LANDSAT LANDSAT SPOT NOAA MOS JERS ADEOS IRS-1C IRS-1C 

SYSTEM MSS TM XS AVHRR MESSR OPS AVNIR LISS-III WiFS 

VINR 

AND 

SWIR 

Revisit Cycle 16 16 20 (nadir) 1 image/day 17 44 41 (nadir) 24 (nadir) 

(in days) 


Quantization level of remote-sensing data 

Sensor Satellite Level (bit) Descriptions 

MSS LANDSAT 6 8 bits data after radiometric correction 

TM LANDSAT 8 

HRV (XS) SPOT 8 

HRV (PA) SPOT 6 

AVHRR NOAA 10 both 10 and 16 bits’ data are available at distribution 

SAR JERS-1 3 real 3 bits, imaginary 3 bits

Remote Sensing Satellite 

The remote sensing satellites are 

equipped with sensors looking down 

to the earth. They are the "eyes in the 

sky" constantly observing the earth as 

they move around the earth. 

Remote Sensing Satellite 

Remote Sensing satellite images gives a synoptic (bird’s eye) view of 

any places of the Earth surface, which helps to study, map, and 

monitor the Earth’s surface at local and/or regional/global scales. It is 

cost effective and gives better spatial coverage as compared to 

ground sampling. 


Types of Remote Sensing Images 

There are several remote sensing satellite series in operation. 

Different satellite systems have different characteristics, e.g. resolutions, 

number of bands, and have their own importance for different 

application. 

Satellite Systems Spatial Resolution Type Number of Bands Launched by 

LANDSAT-ETM+ 

LANDSAT-TM 

LANDSAT-MSS 

SPOT-XS 

SPOT-PAN 

IRS-1C PAN 

IRS-LISS-III 

IRS-WiFS 

Cosmos -KVR1000 

IKONOS 

IKONOS 

ADEOS-AVNIR M 

NOAA AVHRR 

MOS MESSR 

15,30,50 

30m 

80m 

20m 

10m 

6m 

24m 

188m 

2m 

1m 

4m 

16m 

1.1Km 

50m 

Multi-spectral 




Panchromatic 

Panchromatic 



Panchromatic 

Panchromatic 





8 

7 

4 

3 

1 

1 

4 

2 

1 

1 

4 

4 

5 

4 

USA 

USA 

USA 

France, Sweden 

France, Sweden 

India 

India 

India 

Russia/USA 

Canada 

Canada 

Japan 

USA 

Japan 



SATELLITE LANDSAT LANDSAT4/5 SPOT NOAA MOS JERS ADEOS IRS-1C IRS-1C 

SYSTEM 

4/5 

TM 

XS AVHRR 

MESSR 

OPS AVNIR LISS-III WiFS 

SOME 

VINR 

MSS 

OPTICAL 

and 

SENSOR 

SWIR 

SYSTEM 

Spectral 

Resolution Four Seven Three Five Four Seven Four Four Two 

(Number of 

Bands) 

Spectral ranges (wave-length portion of EMR) in µm (micrometers) 

Blue 0.45 - 0.52 0.40 - 0.50 

Green 0.50 - 0.60 0.53 - 0.61 0.50 - 0.59 0.51 - 0.59 0.52 - 0.60 0.52 - 0.62 0.52 - 0.59 

Red 0.60 - 0.70 0.62 - 0.69 0.62 - 0.68 0.58 - 0.68 0.61 - 0.69 0.63 - 0.69 0.62 - 0.72 0.62 - 0.68 0.62 - 0.68 

NIR 0.70 - 0.80 0.78 - 0.90 0.78 - 0.88 0.73 - 1.10 0.72 - 0.82 0.76 - 0.86 0.77 - 0.86 0.77 - 0.86 

NIR 0.80 - 1.10 0.80 - 1.10 0.82 - 0.92 

IIR 1.57 - 1.78 1.60 - 1.71 1.55 - 1.75 

IIR 2.10 - 2.35 3.55 - 3.93 2.01 - 2.12 

IIR (MIR) 2.13 - 2.15 

IIR (MIR) 2.27 - 2.40 

ThIR 10.45 - 11.66 10.3 - 11.2 

FIR 11.5-12.5 


Remote Sensing Images 

Remote sensing images are normally in the form of digital images. 

Image processing techniques are applied to enhance the image to help 

visual interpretation, information extraction and to correct or restore 

the image if the image has been subjected to geometric distortion, blurring 

or degradation by other factors. There are many image analysis techniques 

available and the methods used depending upon the requirements of the 

specific problem concerned. 

Satellite Image of Kathmandu

Remote Sensing

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