CE 1125
Surveying
Faruque Abdullah
Lecturer, Dept. of BECM, RUET
Class Lecture – 04
Date: 30/03/2022
Remote Sensing
Remote Sensing
Remote sensing is the art or science of
obtaining information about an object, an
area or a phenomena, through analyzing of
data collected by a given device or sensor
that has no direct physical contact with the
object, area or phenomena being
investigated. In simple terms, remote
sensing is the process of acquiring data or
information about an object without any
physical contact.
Principles of Remote Sensing
Remote sensing involves the detection and D
measurement of the radiations of different A
G
wavelengths reflected or emitted from distant
B E
objects or materials, which helps in their
identification and categorization. It offers the
following basic components to measure: C F
✓ Energy Source or Illumination (A): The first requirement for remote sensing is to have an energy
source which illuminates or provides electromagnetic energy to the target of interest.
✓ Radiation and the Atmosphere (B): As the energy travels from its source to the target, it will come
in contact with and interact with the atmosphere it passes through. This interaction may take place
a second time as the energy travels from the target to the sensor.
Principles of Remote Sensing
✓ The Interaction with the Target (C): Once the energy makes its way to the target through the
atmosphere, it interacts with the target depending on the properties of both the target and the
radiation.
✓ Recording of Energy by the Sensor (D): After the energy has been scattered by, or emitted from
the target, we require a sensor (remote - not in contact with the target) to collect and record the
electromagnetic radiation.
D
✓ Transmission, Reception, and Processing (E): A
G
The energy recorded by the sensor has to be
transmitted, often in electronic form, to a B E
receiving and processing station where the data
are processed into an image (hardcopy and/or
C F
digital).
Principles of Remote Sensing
✓ Interpretation and Analysis (F): The processed image is interpreted, visually and/or digitally or
electronically, to extract information about the target which was illuminated.
✓ Application (G): The final element of the remote sensing process is achieved when we apply the
information we have been able to extract from the imagery about the target in order to better
understand it, reveal some new information, or assist in solving a particular problem.
D
A
G
B E
C F
Classification of Remote Sensing
Remote sensing is broadly classified into two categories:
✓ Passive remote sensing: It uses sun as a source of EM energy and records the energy that is
naturally radiated and/or reflected from the objects.
✓ Active remote sensing: It uses its own source of EM energy, which is directed towards the
object and return energy is measured.
Passive Remote Sensing Active Remote Sensing
Electromagnetic Radiation
Electromagnetic radiation (EMR) describes the way in which high-frequency energy (visible
light, radio waves, heat, ultraviolet rays and x-rays) is transferred from one object to another
through space.
✓ The sun is the main source of electromagnetic radiation.
✓ The electromagnetic radiation is normally used as an information carrier in remote sensing.
Wavelength region and their application in remote sensing
Wavelength region and their application in remote sensing
Band Wavelength Nominal Spectral Principal Applications
Location
1 0.45 – 0.52 Blue Useful for coastal water mapping as it is designed for water body
penetration. Also useful for forest type mapping, soil/vegetation
discrimination and cultural feature identification.
2 0.52 – 0.60 Green Useful for vegetation discrimination and vigor assessment as designed to
measure green reflectance peak of vegetation. Also useful for identification
of cultural feature.
3 0.63 – 0.69 Red Aiding in plant species differentiation, as it is designed o sense in a
chlorophyll absorption region. Also useful for identification of cultural
feature.
4 0.76 – 0.90 Near infrared Useful for determination of vegetation types, vigor, and biomass content for
soil moisture discrimination and for delineating water bodies.
5 15.5 – 1.75 Mid infrared Useful for determining of vegetation moisture content, soil moisture
discriminations and thermal mapping applications.
6 10.4 – 12.5 Thermal infrared Useful in vegetation stress analysis, soil moisture discrimination and
thermal mapping applications.
7 2.08 – 2.35 Mid infrared Useful for discrimination of types of mineral and rock and determination of
vegetation moisture content.
Application of Remote Sensing
Application in agriculture:
✓ Crop identification
✓ Crop acreage estimation
✓ Crop condition assessment and stress detection
✓ Identification of planting and harvesting dates
✓ Crop yield modeling and estimation
✓ Identification of pest and disease infestation
✓ Soil moisture estimation
✓ Irrigation monitoring and management
✓ Soil mapping
✓ Monitoring of draughts
✓ Land cover and land degradation mapping
✓ Identification of problematic soils
Different Phases of Railway Project Survey
Application in Urbanization & Transportation:
✓ Urban planning
✓ Roads network and transportation planning
✓ City expansion
✓ City boundaries by time
✓ Wetland delineation
Different Phases of Railway Project Survey
Application in Natural resource Management:
✓ Forestry: Monitoring urban forestry, forest deforestation
✓ Water source management
✓ Habitat analysis
✓ Environmental assessment
✓ Impervious surface mapping
✓ Hydrology
✓ Mineral province
✓ Geomorphology
Land use
Land cover means any surface cover on the ground which can include vegetation, urban infrastructure,
water, lake, mountain, transportation networks, buildings or any other. The attributes measured by remote
sensing techniques relate to land cover, from which land use can be inferred, particularly with ancillary
data or a priori cognition.
Advantages of Remote Sensing
✓ Provides a view for the large region
✓ Offers Geo-referenced information and digital information
✓ Most of the remote sensors operate in every season, every day, every time and even in real
tough weather
