Kerala State Syllabus 10th Standard Social Science Chapter 6 Eyes in the Sky and Data Analysis Important Questions

Answer the following. Score 1 each

Choose the correct answer.

Question 1.
Remote sensing generally used to gather clear – information about comparatively small areas.
Terrestrial photography
Aerial remote sensing
Satellite remote sensing
Answer:
Aerial remote sensing

Question 2.
Which of the following is related to sun-synchronous satellites?
Helps in continuous data collection.
Move-in accordance with earth’s rotation.
Repetitive data collection is possible.
Answer:
Repetitive data collection is possible.

Question 3.
Which of the following indicates high spatial resolution? ,
5 m spatial resolution
1 km spatial resolution
1 m spatial resolution
Answer:
1 m spatial resolution

Question 4.
The system developed by USA to understand about the latitude, longitude and elevation of objects on earth’s surface.
GIS
GPS
IRNSS
Answer:
GPS

Question 5.
Analytical capability used for analyzing the activities around a point feature or at a definite distance along a linear feature.
Network analysis
Buffer analysis
Overlay analysis
Answer:
Buffer analysis

Question 6.
A sensor with high spatial resolution can distinguish
features of land and sea
multistoreyed buildings
small vehicles
Answer:
small vehicles

Question 7.
The Social Science Club of your school has decided to prepare a sketch of your school and to give it to the Panchayat authorities. Which instrument can be used to display the latitude of the school used for telecommunication?
Global Positioning System
Scanner
Satellite
Answer:
Global Positioning System

Question 8.
Which among the following is not related to Geographic Information System?
Overlay analysis
Buffer analysis
Overlap
Answer:
Overlap

Question 9.
The size of the smallest object on the earth’s surface that a satellite sensor can distinguish is called sensor’s .
Spectral signature
Spatial resolution
Temporal resolution
Answer:
Spatial resolution

Question 10.
The instrument used to obtain the three-dimensional view of aerial photographs
Telescope
Stereoscope
Kalidoscope
Answer:
Stereoscope

Question 11.
Which is more suitable for repetitive data collection?
Aerial remote sensing
Terrestrial photography
Satellite remote sensing
Answer:
Satellite remote sensing

Question 12.
The geostationary satellites of India are included in the series of
INSAT
IRS
Challenger
Answer:
INSAT

Question 13.
Write the name of a pair of aerial photos with overlap.
Answer:
Stereo pair

Question 14.
Name the two types of data essential for analysis in GIS.
Answer:

1. Spatial date
2. Attributes

Question 15.
Which type of analysis in GIS can be used for identifying the roads with least traffic as part of town planning?
Answer:
Network analysis

Question 16.
Identify the type of analysis in GIS used for studying the relationship between different spatial information of an area.
Answer:
Overlay analysis

Question 17.
Name the system which helps in sensing the latitudinal and longitudinal location and elevation of objects on the earth’s surface with corresponding time.
Answer:
Global Positioning System

Question 18.
Which among the following is the most suitable method for understanding the seasonal growth rate of crops in an extensive agricultural land?
Aerial remote sensing
Satellite remote sensing
Field survey
Answer:
Satellite remote sensing

Institutions with responsibility for aerial survey
National Remote Sensing Centre Hyderabad
Indian Aerospace Company – Kolkata

B. Answer in a sentence each.

Question 1.
From which year onwards was data collection using satellite remote sensing started?
Answer:
1960

Question 2.
Name the invention which paved the way for a great change in data collection in the 19th century.
Answer:
Photography

Question 3.
Which is the platform used to place the camera to take pictures from great heights?
Answer:
Aircrafts

Question 4.
The remote sensing not suitable to take photographs of regions on earth that are vast and extensive.
Answer: ‘
Aerial remote sensing

Question 5.
Which is the satellite that orbits along with the rotation of the earth?
Answer:
Geostationary satellites

Question 6.
Which is the satellite suitable for data collection about natural resources and land use pattern?
Answer:
Sun-synchronous satellites

Question 7.
Which is the indigenously developed satellite-based navigation system of India?
Answer:
IRNSS – Indian Regional Navigation Satellite System

Question 8.
Which is the satellite used for understanding about weather conditions?
Answer:
Geostationary satellites

Question 9.
What are sensors?
Answer:
Instruments used for data collection through remote sensing are called sensors.

Oases easily distinguished by
Sensors record the reflection of electromagnetic radiation of objects. The spectral signature of sand is different from that of plants. So the oases in deserts can be easily distinguished by remote sensing.

Answer the following. Score 2 each

Question 1.
What is remote sensing? By which name are the instruments for this known?
Answer:
The method of collecting information about an object, or a phenomenon with the help of place satellites without actual physical contact is known as remote sensing.

The instruments used for data collection about the earth’s surface are known as sensors.

Question 2.
Answer the following.
a. Remote sensing carried out with the help of solar energy.
b. Remote sensing made with the help of artificial source of energy.
Answer:
a. Passive remote sensing
b. Active remote sensing

Question 3.
Which type of satellites are INSAT, IRS and Landsat of India?
Answer:

• IRS and Landsat are sun-synchronous satellites.
• INSAT satellites are geostationary satellites.

Question 4.
If that is satellite remote sensing? By what name is the sensor known in this?
Answer:

• The process of collecting information using sensors fitted on artificial satellites is called satellite remote sensing.
• Sensors in artificial satellites are known as ‘scanner’.

Question 5.
Which are the geographical regions coming under the surveillance of IRNSS? ‘
Answer:
IRNSS is India’s indigenously developed satellite-based navigation system. It has a radius of 1500 km around including India, Pakistan-, China and the Indian Ocean.

Question 6.
GPS developed by USA determines position with the help of many satellites. Explain.
Answer:
GPS is America’s satellite-based navigation system. A group of 24 satellites placed at different orbit between the altitudes 20000 and 20200 km above the earth’s surface locate objects. We can locate places with the help of the signals received from the satellites in our handheld device.

Question 7.
Write any two uses of GIS
Answer:

1. To conduct thematic studies.
2. To represent geographical features spatially.

Question 8.
What are the possibilities of remote sensing technology in agricultural sector?
Answer:

• For collecting data about the extent of crops and spread of pest attacks.
• For understanding land use of an area.
• To locate places with greater ground water potential.
• For monitoring of drought and flood.

Question 9.
A study tour is planned from your school. Can network analysis of GIS be made use here? Which of your needs related to study tour can be solved using this analysis? Write any three.
Answer:
Network analysis of GIS can be made use for the study tour.
Network analysis can be useful for planning study tour in the following ways.
i. To identify the route with hospitals, hotels and petrol pumps on the way.
ii. To identify the easiest and less congested roads from one place to another.
iii. Plan maximum number of attractive destinations in the available time.
iv. Help to bring accident victim to a suitable hospital through less congested roads.

Question 10.
Do all objects have similar spectral signatures? Why?
Answer:

• No. The amount of electromagnetic radiation that is reflected by an object is called spectral signature.
• Spectral signatures vary for different objects depending upon their physical characters.

Question 11.
What is overlap in aerial photographs? Mention the advantage of the photographs having overlap.
Answer:
In each aerial photograph 60 percent of the places depicted in the adjacent photo is included. This is termed as the overlap in aerial photos. This is done for ensuring continuity and to obtain three-dimensional vision using a stereoscope.

Question 12.
Write four instances in which the possibility of the technology of remote sensing can be used in Kerala.
Answer:
i. For estimating the area of paddy cultivation.
ii. Detecting forest fire, as they are common in Kerala during summer.
iii Identifying a drought-affected area.
iv. Exploring groundwater.
v. Identify areas prone to flood and to prepare flood predicting model.

Question 13.
What are the characteristics of sensors?
Answer:

• Spectral signature
• Spatial resolution

Question 14.
Complete the flow chart.

Answer:
a. Aerial remote sensing
b. Satellite remote sensing

Question 15.
The given information are concerned with two methods of remote sensing. Name these two methods.
Answer:
a. Captures continuous photographs of the places over which the aircraft passes.
b. Gathers information using sensors fitted in artijicial satellites.

Question 16.
Explain the importance of stereoscopes in aerial remote sensing?
Answer:

• Helps in obtaining three-dimensional view from aerial photos with overlap.
• To get the synoptic view of an area and to identify the undulations of the terrain.

Question 17.
Both spatial data and attributes are essential for analysis in GIS. Write any four attributes regarding your school.
Answer:

• Number of students
• Number of teachers
• Number of classrooms
• School building is single or multi-storied.

Answer the following; Score 3 each

Question 1.
What are sensors? How do they work? Write example for sensors.
Answer:

• The instruments used for data collection through remote sensing are called sensors.
• Sensors work with the help of electromagnetic radiations. Sensors record the electromagnetic radiations emitted or reflected by objects.
• Examples are camera and scanner.

Question 2.
How is remote sensing classified based on the source of energy? Why?
Answer:

Based on the source of energy, remote sensing can be classified into active remote sensing and passive remote sensing.

Active remote sensing: Remote sensing made with the aid of artificial source of energy radiating from the sensor is known as active remote sensing.
Eg: flash in camera Passive remote sensing: Remote sensing made with the help of solar energy is known as passive remote sensing. In this, the sensors do not emit energy by it self.

Question 3.
Two kinds of data are necessary for data analysis in GIS. Which are they?
Answer:

1. Spatial data
2. Attributes

Question 4.
What is a platform? Write examples for different types of platforms.
Answer:

• The carrier on which sensors are fixed for data collection is known as platform.
• The platforms where cameras are placed: aircraft, bai loons, cranes.
• The platform where sensors are placed: satellites.

Question 5.
How is remote sensing classified based on the platform used? Explain.

Answer:
Based on the type of platform used, remote sensing is classified into three: They are

1. Terrestrial photography
2. Aerial remote sensing
3. Satellite remote sensing

Terrestrial photography: The method of obtaining the earth’s photography using cameras from the ground is called terrestrial photography. Eg: photography we take using cameras.

Aerial remote sensing: The method of obtaining photographs of the earth’s surface continuously from the sky by using cameras mounted on aircraft is known as aerial remote sensing.

Satellite remote sensing: The process of gathering information using sensors fitted on artificial satellites is known as satellite remote sensing.

Question 6.
Identify from the pictures, the platforms used to collect information. Also write the name of sensors placed in these.

Answer:
Platform in Fig. A. Earth. Sensor used is camera.
Platform in Fig. B. Aircraft. Sensor used is camera.
Platform in Fig. C. Satellite. Sensor used is scanner.

Question 7.
What are the merits of aerial remote sensing?
Answer:

• Useful to gather clear information about comparatively smaller areas.
• Stereoscopic vision will give a synoptic view of the area.
• Highly useful for obtaining photographs with three-dimensional view.
• Three dimensional view enables in understanding the undulations of the terrain.
• Information on any region can be gathered in accordance with our requirements.

Question 8.
What is overlap in aerial photographs? Mention its advantage.
Answer:
In each aerial photograph, nearly 60% of the places depicted in the adjacent photo is included. This is done to ensure continuity and to obtain three dimensional view. This is termed as the overlap in aerial photos. Only photos with overlap can give three dimensional views.
Its advantages are :

• To ensure continuity of aerial photographs.
• To obtain three dimensional view
• For a synoptic view of the area.
• Help in understanding the undulations of the terrain.

Question 9.
Why are geostationary satellites called so? What are its uses?
Answer:
Geostationary satellites are the satellites that move in equal velocity with the earth’s rotation, As the movement of these satellites corresponds to the speed of rotation of the earth, it stays constantly above a specific place on earth. As it stays constantly above a specific place on earth, they are called geostationary satellites.
Uses:

• Helps in continuous data collection of an area.
• Used in Telecommunication and weather studies.

Question 10.
What is spectral signature? Write the reason for difference in the amount of spectral signature.
Answer:
The amount of reflected energy by each object is called spectral signature. Each object on the earth’s surface reflects electromagnetic radiation differently.

The difference in the amount of reflection is because of the variations in the physical properties of objects.
For eg: The spectral signature of sand is different from that of vegetation.

Question 11.
What is spatial resolution? How does it influence the study of the surface of the earth?
Answer:
Spatial resolution of a sensor is the size of the smallest object on the earth’s surface that it can recognize.
The sensors fitted on state 11 items cannot recognize objects of all sizes on the surface of the earth. Earlier sensors were able to distinguish only large objects and they had less resolution (Eg, 1 km). Today there are sensors that can even represent information of less than one meter. Houses, vehicles and trees can be recognized by such high-resolution sensors.

Question 12.
What is Geographic Information System? What are the possibilities of GIS softwares?
Answer:
Geographic Information System is a computer-based information management system by which the data collected from the sources of information like maps, aerial photographs, satellite imageries, tables, surveys, etc. are incorporated into the computer using softwares, which are retrieved, analyzed and displayed in the form of maps, tables and graphs.
Uses

• Exhibit the maps
• Renew/update the maps
• Produce new maps
• Analysis and preparation of maps and graphs based on data acquired.

Question 13.
What is the importance of preparing layers in GIS? Write an example.
Answer:
With the help of GIS softwares, spatial data can be converted into different layers. The thematic maps prepared and stored in Geographic Information System for analytical purpose are called layers. When the features of the surface of the earth are converted into layers, we can easily make maps or tables for our preference from this. The spatial relationship among the features on the surface of the earth can easily be understood by analyzing the appropriate layers.

Example: using, GIS software, different data about India can be depicted as separate layers. Different layers to show the states in India, natural resources, mountains, cotton cultivated regions and jute cultivated regions can be depicted. Maps obtained as different layers in this manner can be used for different analyses.

Question 14.
Network analysis is very useful to travellers. Substantiate.
Answer:

• Helps to find out the easiest and less congested roads from one place to another.
• Helps tourists to plan maximum number of attractive destinations in the available time.
• Helps to find routes without tolls.
• Helps to identity the petrol pumps, hotels and hospitals on the way.
• Helps to bring accident victims to a suitable hospital through less congested roads.

Question 15.
Which country’s satellite-based navigation system is GPS? Write its uses.
Answer:

• USA has developed GPS for defense.
• Useful in map making and transport.
• Displays the latitude, longitude, height, and time of a place.

Question 16.
What is overlay analysis? Write its uses.
Answer:
Overlay analysis is used to identify the mutual relationships among the various surface features on earth and the periodic changes undergone by them.
Uses

• To know the changes in the area of crops.
• To know the changes in land-use patterns.
• To know the changes in the agricultural crops.

Question 17.
What is the name of the satellite based navigation system developed by India? Write its peculiarities.
Answer:
IRNSS is the satellite based navigation system of India as an alternative to GPS. Apart from India, a radius of 1500 kms including the Indian Ocean and the countries like Pakistan and China come under its surveillance.

Question 18.
The water level in the reservoir increased beyond the limit. The authorities decided to open the shutter of dam and let the water flow into the river. To know how much-area will be flooded due to the overflowing river,
a. Which analytical capability of Geographic Information System can be made use here?
b. Write another example for this analytical capability.
Answer:
a. Buffer analysis of a linear feature. In this, the detailed information regarding the area and the people living on the banks of the river can be collected. A parallel zone can be created aside a linear feature like river. It shows the area of
land that will get flooded.
b. Example:

• The width of a road in a region is increased from 5 m to 8 m. Using buffer analysis, it can be easily determined as to how much land belonging to local people has to be acquired and how many people will become homeless.
• If the width of the road is increased by 5 m on either side, how many people would lose land.
• If the width of the road is increased only on the left side by 10 m, how much land has to be acquired and how many will become homeless.

Question 19.
How do spatial data and attributes differ? Explain with example.
Answer:
Each feature on the earth’s surface has a location of its own. Such features of the earth’s surface having a specific location are known as spatial data. For eg: among the countries of the world, the location of India is between north latitudes 8°4′ and 37°6′ and east longitudes 68°7′ and 97°25′.

The additional information about the characteristics of each data on the earth’s surface are called attributes. The characteristics of spatial data can be recorded with the help of their attributes. For eg: when we find out the location of well in our house, it forms spatial data. When we collect information about the characteristics of the well like its depth, whether it has a platform or retaining wall, these are its attributes.

Question 20.
Suppose our government plans to build a Highway in our state. ‘
a. Which technique in geography can be used for its planning? .
b. Which technique can be used to assess the extent of land lost?
c. Which technique can be used to assess the compensation and to estimate the land holdings of similar size?
Answer:
a. Geographic Information System
b. Buffer analysis
c. Overlay analysis

Question 21.
Suppose you are analysing the satellite imageries of two strategically important locations A and B. The spatial resolutions of the imageries are 1km x 7km and lm x 1m respectively.
i. Which of these imageries are of high spatial resolution?
ii. Which of these imageries cannot be utilized for microlevel studies?
iii. What do you mean by the term spatial resolution?
Answer:
i. Imagery B has high, spatial resolution.
ii. Imagery A cannot be utilized for micro-level studies.
iii. The size of the smallest object on earth that can be recognized by the sensor is the spatial resolution of that sensor.

Question 22.
In each aerial photograph, nearly 60% of the places depicted in the adjacent photo is included.
i. What is the significance in doing so?
ii. Mention the name by which it is known.
Answer:
i.
For the continuity of photographs.
To obtain three-dimensional view
ii. Overlap

Question 23.
As a result of the landslide in Kavalappara in Malappuram district, a large area was destroyed and many became homeless. The Government decided to estimate the extent of land area destructed and to identify the real land owners using GIS. Which analytical capabilities of GIS can be made use of for each purpose? Explain.
Answer:
To estimate the area of land destructed, buffer analysis can be used. The spatial data of the area of landslide are subjected to buffer analysis, and a special circular zone is created. This helps to estimate the houses and agricultural lands of the area.

To find the real landowners, overlay analysis can be used. Overlay analysis is used for under-standing the mutual relationship among the various features on the earth’s surface and the periodic changes undergone by them.

Question 24.
The continuous numbers of a series of aerial photographs are given.

a. Can we call the photographs 41 and 45 together as stereopair? Why?
b. What is the peculiarity of stereopairs?
c. Which are the pairs of photograph 42?
Answer:
a. No. Photographs 41 and 45 are not stereopairs. Two adjoining aerial photographs with overlap are called stereopairs.
b. When a stereopair is observed through a stereoscope, three dimensional view is obtained.
c. Photographs 41 and 43.

Question 25.
Classify the following as spatial data and attributes.

• Kerala
• Lakshadweep
• Mizoram
• Distribution of rainfall
• Vegetation
• Population

Answer:

• Spatial data: Kerala, Mizoram, Lakshadweep
• Attributes: Population, vegetation, distribution of rainfall.

Answer the following. Score 4 each

Question 1.
Complete the given flow chart.

a. …………..
b. …………..
c. ………….
d. ………….
e. ………….
Answer:
a. The shaking of the aircraft affects the quality of photos.
b. Open space is needed for the takeoff and landing of aircraft.
c. not practical to take photographs of vast and extensive regions.
d. Costly to land the aircraft frequently for refueling.
e. The advent of satellite remote sensing.

Question 2.
Which are the two types of satellites in satellite remote sensing? Write their features.
OR
INSAT and IRS are two types of satellites launched by India. Which type of satellites are these? Distinguish between them.
Answer:
Geostationary satellites and sun synchronous satellites.

1. INSAT is geostationary satellite.
2. IRS is sunsynchronous satellite.

Geostationary satellites

• Orbit the earth at an elevation of about 36000 km. above the earth.
• Move in equal velocity with earth’s rotation.
• As their movement corresponds to the speed of rotation of the earth, it stays constantly above a specific place on the earth. This helps in continuous data collection of an area.
• One third of the earth comes under its field of view.
• Useful for weather studies and in tele-communication.

Sun synchronous satellites

• The orbit is about 900 km in altitude.
• Revolve around the earth along the poles.
• The field of view is less.
• Repetitive data collection of a region at regular interval is possible.
• Used to collect data on natural resources, land use and ground water.
• Surveillance area is less than that of geostationary satellites.
• Mainly used for remote sensing purpose.

Question 3.
One of the uses of remote sensing technology is given. Add more.

Answer:
a. For ocean exploration.
b. For oil explorations.
c. To locate places with groundwater potential.
d. To collect data about the extent of crops and the spread of pest attacks.
e. For monitoring of drought and flood.
f. For identifying forest fires in deep forests and for taking control measures.

Question 4.
What is the importance of spatial data and attributes in map making? Explain with example.
Answer:
Each feature on the earth’s surface has a location of its own. Such features of the earth’s surface having a specific location are known as spatial data. For example, the location of Trivandrum is in between north latitude 8°29′ and east longitude 76°55′. When the map of a place is to be included in G1S, its spatial data should also be given. The latitude and longitude of that place should be marked in the map.

Along with spatial data, attributes should also be included in the map. The additional information about the characteristics of each spatial data on earth’s surface are called attributes. For example, if a well is to be marked in the map, information about the characteristics of the well such as the depth of the well, whether it has a platform and retaining wall, whether it is fresh water or not and details of ownership of the well should also be marked. These are the attributes of the well.

Question 5.
One of the uses of GIS is given. Add more.
Conduct thematic studies.
Answer:

• To represent geographical features spatially.
• To update and incorporate data easily.
• To generate visual models of future phenomena and processes based on collected data.
• For making maps, graphs and tables for specific needs.
• To compile data from different sources.

Question 6.
Write the uses and working of GPS.
How can the techniques of satellite remote sensing and geographic information system be made use of in the following areas?
Answer:
Uses: Helps in sensing latitudinal and longitudinal location, elevation of objects on earth’s surface along with corresponding time.

Working : GPS has a group of 24 satellites that orbit around the earth in 6 different orbits between the altitudes 20000 and 20200 km above the earth’s surface to locate objects. We can locate the places with the help of signals received from the satellite in our handheld device. A GPS should receive signals from at least 4 satellites to display the information like latitude, longitude, elevation and time of a place.

Question 7.
The following are statements related to remote sensing. Write what each stands for.
a. The aircraft requires open space for take-off and landing.
b. Photographs with overlap.
c. Orbit the earth at an elevation of about 36000 km above the earth.
d. Repetitive data collection of an area is possible.
Answer:
a. Indicates the limitation of aerial remote sensing
b. Indicates the merit of aerial remote sensing.
c. Geostatiount satellites
d. Sun svplelrronous satellite

Question 8.
Complete the table based on Geostationary satellite and Sun-synchronous satellite.

Answer:

Question 9.
How can the techniques of satellite remote sensing and geographic information system be made use of in the following areas?
a. Agricultural sector
b. Conservation of forest
c. Mapmaking
Answer:
 

Question 10.
A stands for sun-synchronous satellite and B stands for geostationary satellite. How are they useful for the following requirements?
a. For weather studies
b. To locate places with ground water potential
c. Data collection on natural resources.
d. In telecommunication
Answer:
A. Sun-synchronous satellite
a. To locate places with groundwater potential
c. Data collection on natural resources
B. Geostationary satellite
a. For weather studies
b. In telecommunication

Question 11.
The spectral signature of plants is different from that of water bodies. Analyse this statement to answer the questions.
i. What is spectral signature?
ii. Which instrument recognizes spectral signature?
iii. Each object reflects electromagnetic radiation differently. Why?
Answer:
i. The amount of energy reflected by each object is its spectral signature.
ii. Scanners mounted on artificial satellites recognize different objects on the basis of their spectral signature.
iii. Each object on the earth’s surface reflects electromagnetic radiation on the basis of their features. Each object reflects electromagnetic radiation differently. This is because of the difference in the physical property of each object.

Question 12.
Answer the following questions related to remote sensing.
i. What are the features that equip the sun-synchronous satellites for remote sensing?
ii. What are the uses of geostationary satellites?
iii. Write examples for both types of satellites.
Answer:
i. Since sun-synchronous satellites revolve around the earth along the poles, repetitive data collection of a place is possible. Since they travel at a lower elevation, the field of view is less.
ii. Telecommunication Weather studies
iii. Geostationary satellite – INSAT Sun-synchronous satellite – IRS

Question 13.
Overlap is essential for the analysis of aerial photos.
i. What is overlap in aerial photographs?
ii. What do we call two adjacent photographs with overlap?
iii. How does overlap help in the analysis of aerial photographs?
Answer:
i. In each aerial photograph, nearly 60% of the places depicted in the adjacent photos is included. This is known as overlap in aerial photographs.
ii. Stereo pair
iii. When viewed through stereoscope, stereo pair gives a three-dimensional view. This helps in the analysis of aerial photographs. Ensures continuity of the aerial photographs.

Question 14.
Point out the limitations of aerial remote sensing.
Answer:

• The shaking of aircrafts affects the quality of photos.
• The aircrafts require open space for take-off and landing.
• It is not practical to take photographs of regions that are vast and extensive.
• Landing the aircrafts frequently for refueling increases the cost.

Question 15.
Identify the areas where satellite remote sensing techniques can be adopted using geostationary satellites and sun synchronous satellites.
Answer:

• Estimation of loss due to flood.
• Understanding the post-flood conditions of •rivers.
• Assessment of the damages of the areas flooded.
• Preparing flood predicting models by identifying areas vulnerable to flood.

Question 16.
Explain how satellite imageries are prepared.
Answer:
Satellite imageries: Satellite remote sensing is the process of gathering information using the sensors mounted on satellites. Different types of scanners capable of recognizing specific areas in the electromagnetic spectrum are mounted on the artificial satellites. These scanners recognize the different objects on the basis of their spectral signatures and transmit the data to the ground control stations in digital form. These are analyzed with the help of computers and transformed into images. These are known as satellite imageries.

Question 17.
What are the possibilities of satellite remote sensing to overcome ñatural disasters like floods?
Answer:
The possibilities that can be adopted are:
Preparation of flood hazard maps of affected areas.
Estimation of loss due to flood.
Understanding the post flood conditions of rivers.
Assessment of the damages of the areas flooded.
Preparing flood predicting models by ¡dentiI,’ing areas vulnerable to flood.

Question 18.
Geographic Information System is a fast developing technology that can be made use of in different levels of human life. In which all areas can GIS be made use of?
Answer:

• Industry
• Education
• Irrigation
• Transportation
• Disease control
• Tax collection
• Tourism

Answer the following. Score 5 each

Question 1.
What is the significance of the following in collecting data about the earth’s surface?

• Aerial remote sensing
• Overlap
• Stereoscope

Answer:
The indicators given related to aerial remote sensing play an important role in data collection of the earth’s surface and for map making.
Aerial remote sensing
The continuous process of capturing photographs of the earth’s surface using cameras mounted on balloons or aircrafts is known as aerial remote sensing. This is generally used to gather clear information about comparatively smaller areas. Aerial photographs are widely used for the preparation of topographical maps. The most important feature of aerial remote sensing is that it can take photographs that give three dimensional view. Three dimensional view will help in understanding the undulations of the terrain. To get three dimensional view, aerial photographs should have overlap.

Overlap
In each aerial photograph, nearly 60 percent of the places depicted in the adjacent photograph is included. This is done to ensure continuity and to obtain three-dimensional view using stereoscopes. This is known as overlap in aerial photographs. Two photographs of adjoining areas with overlap are called stereo pair. When viewed through a stereoscope, the stereo pair will give a synoptic view of the area and will help in understanding the undulations of the terrain.

Stereoscope
Tire instrument that provides three dimensional view from the stereo pairs is called stereoscope.

Question 2.
Explain the role of spectral signature, spatial resolution and sensor in the formation of satellite imageries.
Answer:
The process of gathering information using sensors mounted on artificial satellites is known as satellite remote sensing. Different types of scanners capable of recognizing specific areas in the electromagnetic spectrum are mounted on artificial satellites. These scanners recognise different objects on the basis of spectral signatures and transmit that information digitally to ground stations. These are analysed with the help of computers and transformed into images. These are known as satellite imageries.

Spectral signature Sensors record electromagnetic radiations that are reflected or emitted by objects. Each object on the earth’s surface reflects electromagnetic radiation differently. This difference in the amount of reflection is because of the variations in the physical properties of objects. The amount of reflected energy by each object is called the spectral signature of that object.

Spatial resolution
Sensors fixed on satellite cannot recognize objects of all sizes on the earth’s surface. Sensors with low spatial resolution can only distinguish big objects on the earth’s surface. Eg: Land, sea, hills, forests, etc. The recently developed high spatial resolution sensors can distinguish houses, vehicles, trees, etc. Spatial resolution of a sensor is the size of the smallest object on the earth’s surface that it can recognize.

Sensors
Instruments used for data collection through remote sensing are called sensors. Camera and scanners are sensors. Sensors work with the help of electromagnetic radiations. Sensors record electromagnetic radiations that are reflected or emitted by objects.

Question 3.
What is the use of satellite-based navigation system? How is it made possible? Explain the progress of India in this area.
Answer:
Today satellite based navigation systems are used for monitoring the location and movement of objects on the earth’s surface. It is used in several sectors like map making, transportation, etc. The most important among these is the Global Positioning system of the USA.

In this system, a series of 24 satellites placed at different orbits between the altitudes 20000 and 20200 km above the earth’s surface locate objects. We can locate places with the help of the signals received from the satellites in our handheld device. The GPS requires signals from atleast four satellites to display information like latitude, longitude, elevation, time, etc. This facility is now open to the public since 1980.

IRNSS is a satellite-based navigation system developed by India as an alternative to of GPS. It has radius of 1500 km including India, Pakistan, China and the Indian Ocean. Of the 7 satellites planned, all have been launched.

Answer the following. Score 6 each

Question 1.
Aerial remote sensing has many merits. At the same it has many limitations also. Substantiate.
Answer:
The continuous process of capturing photographs of the earth’s surface using cameras fixed on balloons or aircrafts is known as aerial remote sensing. It has many merits and limitations.

Merits

•  Useful for collecting clear information about comparatively smaller areas.
• Widely used for the preparation of topographical maps.
• Useful for obtaining photographs with three dimensional view.
• Three dimensional view enables to understand undulations of the terrain.
• Useful for synoptic view of the area.

Limitations

• The shaking of the aircraft affects the quality of photos.
• Open space is needed for the take off and landing of aircrafts.
• Not practical for taking photographs of vast and extensive regions.
• Costly to land the aircraft frequently for refuelling.

Question 2.
What are the possibilities of GIS? How are these possibilities beneficial to humans? Explain.
Answer:
Softwares are used for preparing maps with the help of data collected through remote sensing and other methods of survey. These softwares are also used for incorporating details in the maps and analyzing them for various purposes. This system is known as GIS.

The surface features of the earth collected as spatial information and attributes can be analysed by GIS in various ways according to the requirements. The analytical capabilities of GIS are network analysis, buffer analysis and overlay analysis.

Overlay analysis: Overlay analysis used to identify the interrelationship of various surface features on earth and the changes they have undergone over a period of time. This analysis is helpful in understanding the changes in the area of crops, the changes in land use, etc. Suppose we have a map showing the paddy cultivation in Thrissur district in 2000. If we want to understand the changes in the area of paddy cultivation by the year 2015, all we have to do is overlay the corresponding map.

Buffer analysis: This is an analysis capability used for analysing the activities around a point feature or at a definite distance along a linear feature.

Network analysis
Linear features such as roads, rivers and railway are subjected to network analysis. Using this, we can find the shortest route to reach a place, routes with less traffic, routes without toll and can identify petrol pumps, hospitals and hotels.

For Extra  Reading

A Peep into the History of Remote Sensing
First phase: Before 1925

• During earlier times, photographs of Paris city were taken using cameras tied to domestic pigeons.
• Photographs taken in this manner did not have a precise continuation or control.
• Afterwards, balloons began to be used.
• In 1858 Gaspard Felix took a photograph of a place called Beaver in France using balloon.

Second phase: 1925 – 1945

• The use of aerial photographs for collecting information about the earth’s surface became more widespread.
• Camera lenses were used effectively.
• Advanced aircrafts began to be used.
• Aerial photographs were used greatly in the second world war.

Third phase: 1945 – 1960

• Aerial photographs began to be used in various fields.
• Such photographs were widely used for theme based studies.

Fourth phase: 1960 – 1972

• Satellite remote sensing was started. ,
• Earth observation from the outer space started.

Fifth phase: After 1972

• America successfully launched the Landsat series of satellites.
• India successfully launched several satellites such as Cartosat, Resources at, and Oceans.

Institutions that use Remote Sensing in Kerala
Various central and state departments in Kerala and many private companies make use of remote sensing technology.

• Kerala State Remote Sensing and Environment Centre (KSRSEC)
• Centre for Earth Science Studies (CESS)
• Centre for Water Resources Development and Management (CWRDM)
• Kerala Forest Research Institute (KFRI)
• Kerala State Land Use Board (KSLUB)
• Geological Survey of India (GSI)
• Central Ground Water Board (CGWB)
• Central Marine Fisheries Research Institute (CMFRI)