remote sensing Flashcards
In-situ Data Collection
- Weather Stations
- Soil Sampling
- Water Quality Monitoring
- Biological Surveys
Limitations of In-situ Data Collection
Time and Labor Intensive
* Limited Coverage
* Accessibility Issues
Remote Sensing?
information about objects,
areas, or phenomena from
a
distance, typically using
satellite or airborne sensors
to gather data.
launched the first weather
satellite,
On 1 April 1960 U.S. launched the first weather
satellite, TIROS-1
The first satellite dedicated to Earth
observation.
On 23 July 1972 U.S. launched Landsat-1
The first satellite dedicated to Earth
observation.
India’s first satellite was
Aryabhata, which was launched
on April 19, 1975
state-of-art remote sensing satellites, was
successfully launched into a polar sun-
synchronous orbit
IRS-1A, 1988
Atmospheric Window
atmospheric window refers
to specific ranges of
wavelengths in the
electromagnetic spectrum
In these windows,
energy can pass through the
atmosphere with minimal
absorption and scattering,
making it easier for remote
sensing instruments to capture
data from the Earth’s surface.
10
Captures clear water bodies and vegetation characteristics.
shallow water studies, as well as vegetation mapping.
Green Band
Detects vegetation health and chlorophyll content.
assessing forest density and agricultural health.
Red Band
plants absorb red light for photosynthesis.monitoring crop health and creating vegetation indices (like NDVI).
Near Infrared
NIR is highly reflective in healthy vegetation due to its cellular structure. It is used for vegetation mapping, distinguishing water bodies, soil analysis, and tracking plant health.
Shortwave Infrared
Differentiates between dry and moist vegetation and can distinguish among various rock types.
drought assessment, soil moisture mapping, and geological studies.
Thermal Infrared
Detects heat emitted by objects.wildfire detection, urban heat studies, and water temperature monitoring.
Microwave
Penetrates clouds, rain, and some vegetation; suitable for all-weather, day-night observations.
radar imaging for topography, agriculture (soil moisture), and disaster monitoring (floods,
landslides).
Passive Sensing:
Relies on natural radiation from the Sun.
Useful for daytime observations in the
visible, NIR, and thermal infrared bands.
Active Sensing:
Generates its own source of radiation (e.g., radar, LiDAR).
- Enables data collection in low-light and cloudy conditions, useful for nighttime and all-
weather imaging. - Example: RADARSAT (microwave radar) and LiDAR systems (laser).
interaction of energy with the Earth’s surface
how
different materials (water, vegetation, soil, etc.) reflect, absorb, and emit electromagnetic radiation
(EMR). These interactions create unique “spectral signatures”
Specular Reflection:
Occurs when energy reflects off smooth surfaces (like calm water
or polished metal) at an equal angle to the incoming radiation.
Diffuse (or Lambertian) Reflection:
Occurs on rough surfaces (like soil, vegetation),
scattering the energy uniformly in all directions.
Absorption
When certain materials absorb specific wavelengths of EM Radiation, they convert the
energy to heat or use it in chemical processes
water strongly absorbs infrared and microwave radiation, while
vegetation absorbs red and blue light for photosynthesis.
Vegetation:
High reflectance in the NIR, low in red (due to chlorophyll absorption), allowing identification of
healthy vegetation.
Water:
Low reflectance in NIR and SWIR, making it easy to identify water bodies.
Soil and Minerals:
Unique patterns in visible, NIR, and SWIR bands, which help in soil classification and mineral
exploration.
Platforms for Remote Sensing
Aerial Platforms
(Airborne)
manned aircraft
drones
Ground-Based
Platforms
stationary towers
manned towers
Satellite Platforms
geo-station orbits
polar(synchronous orbits)