Remote sensing pdf

1. An overview of Remote Sensing
Submitted By Submitted to
Bharat Bimarsa B.C. prof. Umesh Mandel
R-2022-SSC-06M Central Department of Geography
IAAS,TU, Kritipur TU, Kathmandu, Nepal

3. INTRODUCTION
Remote sensing is a technology of acquiring information about earth surface without actually
being in contact with it. Remote sensing is the process of collecting and interpreting information
about an object, area, or phenomenon from a distance without direct physical contact. This is
typically achieved by detecting and measuring the electromagnetic radiation (EMR) reflected,
emitted, or transmitted by the target. Remote sensing is widely used for various purposes, including
environmental monitoring, resource management, agriculture, urban planning, disaster
assessment, and scientific research.
Lillesand and Kiefer (Lillesand and Kiefer, 2000) defined it as 'the science and art of obtaining
information about an object, area, or phenomenon through the analysis of data acquired by a device
that is not in contact with the object, area, or phenomenon under investigation'.

4. REMOTE SENSING PROCESS
How it works
1.Energy Source:
Remote sensing begins with an external energy source, typically the sun. The sun emits electromagnetic
radiation (EMR) across a broad spectrum, including visible light, infrared, and microwave wavelengths.

5. 2.Energy Interaction with Targets:
The emitted or reflected energy interacts with the objects, features, or surfaces on the Earth's surface. The
nature of this interaction depends on the properties of the target material. Different materials absorb, reflect,
or transmit energy in unique ways.
3.Sensor Detection:
Remote sensing sensors, located on satellites, aircraft, drones, or ground-based platforms, detect the
electromagnetic radiation interacting with the Earth's surface. These sensors can be passive or active,
depending on whether they rely on naturally emitted or reflected radiation (passive) or actively transmitted
and detected signals (active).
3.Data Acquisition:
The sensors convert the detected electromagnetic radiation into digital data, creating an image or dataset
representing the characteristics of the Earth's surface. The data may include information about the
reflectance, temperature, or other properties of the target.
4.Data Transmission:
In satellite-based remote sensing, the acquired data is transmitted to ground stations for further processing.
For aircraft and drone-based remote sensing, the data can be transmitted in real-time or stored for later
retrieval.
5.Image Processing:
The raw data undergoes various image processing techniques to enhance its quality and interpretability.
This may involve geometric correction, radiometric calibration, and atmospheric correction to account for
distortions and atmospheric effects.

6. 6.Analysis and Interpretation:
The processed data is analyzed and interpreted to extract meaningful information. This step may involve
identifying land cover types, monitoring changes over time, or assessing environmental conditions.
7.Data Integration:
Remote sensing data is often integrated with other geospatial data, such as maps or geographic information
system (GIS) layers, to provide a comprehensive understanding of the Earth's features.
8.Decision-Making and Applications:
The interpreted data is used for decision-making in various fields. Applications include environmental
monitoring, agriculture, forestry, urban planning, disaster management, and scientific research

7. COMPONENTS OF REMOTE SENSING
1. Platforms
Remote sensing is conducted using various platforms equipped with sensors to capture
information about the Earth's surface, atmosphere, or other features. The choice of platform
depends on the specific application, spatial and temporal requirements, and the type of data
needed.
Remote Sensing platforms can be classified as follows, based on the elevation from the Earth’s
surface at which these platforms are placed.
There are three types of platform in Remote Sensing-
 Ground borne platform
 Airborne platform
 Space-borne platform
Ground borne platform
Ground borne remote sensors are very close to the ground. This platform used to record detail
information about the Earth’s surface closely. The height of the ground-based platform is up to 50
meter from the Earth surface.
Some example of ground-based platform is:
 Ground vehicle
 Tower
 Air balloon

8.  Kite, and others
Airborne platform
Airborne remote sensors are a low altitude or high altitude aerial remote sensing. This is used to
collect very detailed images and facilities the collection of data over any portion of Earth’s surface.
The height of the airborne platform is above 50 km from earth’s surface. It is a very expensive
platform as compared to a ground-based platform.
There are some examples of airborne platform:
 Aeroplane
 High-altitude aircraft
 Drone
 Helicopters, and others
Space-borne platform
The space-borne remote sensors are orbiting spacecraft or space-shuttle on the earth. It is used to
collect information on both the earth’s surface and atmosphere. Also, it coverage large area and
gather more information. Space borne imaging ranges from altitude 250 km to 36000 km.
There are some examples of Space-borne platform:
 Rocket satellite (height is 250 to 300 km above from the Earth’s surface)
 Satellites
 low-level satellite (height is 700 to 1500 km)
 high-level satellites (height is 36000 km)

9. 2. Sensors
There are two types of sensors available in Remote Sensing:
1. Active Sensor
2. Passive Sensor
Active Sensor
Active Sensor is a source of light or illumination and its sensor measures reflected energy. The
energy is generated and sent from the Remote Sensing platform towards the targets.
Radar is an example of Active Sensor.

11. Passive Sensor
Passive Sensor is a source of energy is that naturally available of the Sun. Most of the Remote
Sensing systems work in passive mode, using solar energy as the source of EMR.
The MSS is an example of Passive Sensor.
3. orbits
There are three types of satellite Orbits:
1. Geostationary
2. Sun-synchronous
3. Polar-Orbiting
Geostationary Orbit
A Geostationary Satellite Orbit is a very high altitude (approximately 36,000 km), which views
the same portion of the Earth’s surface.

12. This allows the satellites to observe and collect information continuously over specific areas.
Weather and communications satellites commonly have these types of orbits.

13. Sun-synchronous Orbit
Geo-synchronous Satellite is placed in the geosynchronous orbit, and Earth-centered orbit with
an orbital period that matches Earth’s rotation on its axis, 23 hours, 56 minutes, and 4 seconds.
Since there are 365 days in a year and 360 degrees in a circle, it means the satellites have to shift
its orbit by approximately 1 degree per day. These satellites orbit at an altitude between 700 to 800
km.
Polar Orbit

14. A Polar orbit satellite travels north-south over the poles and takes approximately an hour and a
half for a full rotation. Almost all the satellites that are in a polar orbit are at lower altitudes.
This satellite mostly used for Earth-mapping, observation, capturing the Earth as time passes from
one point.
ELECTROMAGNETIC RADITION

15. Electromagnetic Radiation (EMR) or Electromagnetic energy is the energy propagated in the
form of an advancing interaction between electric and magnetic fields. It travels with the velocity
of light. Visible light, ultraviolet, and infrared rays, heat, radio waves, X-rays all are different
forms of electromagnetic energy.
EMR ranges from gamma rays with very short wavelength to long radio waves. The shortest
wavelengths can also be modeled as particles (photons). The interaction of EMR with matter
forms the basis for Remote Sensing.
EMR Wavelength [µm represented as Microns/micrometers (1,000µm is equal to 1mm.)
APPLICATION OF REMOTE SENSING

16. 1.Environmental Monitoring:
 Deforestation Detection: Monitoring changes in forest cover and identifying areas affected
by deforestation.
 Ecosystem Health: Assessing the health and vitality of ecosystems, including wetlands,
deserts, and grasslands.
 Natural Resource Management: Monitoring water bodies, soil quality, and land use for
sustainable resource management.
2.Agriculture and Precision Farming:
 Crop Health Monitoring: Identifying crop stress, disease outbreaks, and nutrient
deficiencies for targeted interventions.
 Yield Estimation: Predicting crop yields and optimizing agricultural practices for increased
productivity.
 Land Cover Mapping: Mapping land use patterns, identifying field boundaries, and
monitoring changes over time.
3.Urban Planning and Development:
 Land Use Planning: Monitoring urban expansion, assessing infrastructure development,
and managing land use changes.
 Infrastructure Planning: Mapping roads, buildings, and utilities to support urban
development.
 Disaster Risk Reduction: Assessing vulnerability and planning for disaster-prone urban
areas.