Question 1.
Compare active remote sensing and passive remote sensing.
Answer:
Based on the source of energy ór light, remote sensing can be divided into two: active remote sensing and passive remote sensing.
- Remote sensing made with the aid of an artificial sourcç of light or energy radiating from the sensor is known as active remote sensing. Eg: taking pictures using a camera flash. Here camera is the sensor and the flash coming from the camera is the artificial energy source.
- Remote sensing made with the help of solar energy is known as passive remote sensing. Eg: taking pictures without the use of flash.
Question 2.
What is use of overlap in aerial photographs?
Answer:
Each aerial photograph includes about 60 per cent area of the adjacent photographs also. This is called overlap of aerial photographs. Its
advantages are:
- to ensure continuity of aerial photographs
- to obtain three dimension view using stereo scope.
- to give a synoptic view of the area.
- to understand the undulations of the terrain.
Question 3.
Prepare notes on geostationary and sun synchronous sate lilies.
Answer:
Geostationary satellites
Geostationary satellites are those that move in equal velocity with the earth’s rotation.
Orbit the earth at an elevation of about 36000 km above earth.
- One third of the earth comes under its field of view.
- Since they move according to the same orbital velocity of the earth, it stays constantly above a specific place on earth.
- Continuous data collection of an area is possible.
- Used in telecommunication and for weather studies.
- Eg: INSAT satellites of India.
Sun-synchronous satellites
These are satellites that pass around the earth along the poles.
- The orbit is about 900 km in altitude.
- Surveillance area is less than that of geostationary satellites.
- Mainly used for remote sensing purpose.
- Repetitive data collection of a region at regular intervals is possible.
- Used for collecting information about natural resources, land use and groundwater.
- Eg: IRS and Landsat.
Question 4.
List the fields where remote sensing is used.
Answer:
- For exploring the oceans
- For oil exploration ‘ ‘
- For the monitoring of flood and drought.
- For finding out forest fire in deep forests and for taking control measures by monitoring their spread.
- For understanding about the land use in a region.
- To locate places having greater groundwater availability.
- For collecting information about the extent of crops and spread of pest attacks.
Question 5.
What is the merit of using layers in GIS?
Answer:
With the help of GIS softwares, spatial data can be converted into different layers. From these, we can make maps, graphs and tables for our specific needs. Maps obtained as different layers can be used for various analysis.
The spatial relationship among the features on the surface of the earth can easily be understood by analyzing the appropriate layers.
Question 6.
Write down the possibilities of overlay analysis.
Answer:
Used for understanding the mutual relationship among the various surface features on earth and the changes undergone by them over a period of time.
- To identify the agricultural crops of different states.
- To identify the changes in the area of crops.
- To identify the changes in land use pattern.
- To understand the changes in the extent of forests.
- To understand about urbanisation.
- To understand the extent of drought and flood-affected areas
