Basics of Remote Sensing
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Remote sensing involves obtaining information about objects without physical contact. It works by sensing and recording electromagnetic radiation reflected or emitted from targets. The key components are an energy source, sensor, platforms, and data analysis to extract information. Sensors can be optical, thermal, or microwave. Platforms include satellites, aircraft, and ground bases. Applications of remote sensing include agriculture, forestry, geology, hydrology, urban planning, and national security.
Basics of Remote Sensing
- 1. Prepared by: Akash Tikhe (akashtk92@gmail.com) CONCEPTS OF REMOTE SENSING
- 2. NaturalRemoteSensing Sensing / Perceiving Analysis Information / Knowledge Boy or Man ? Name the remote sensing organs in our body?
- 3. ArtificialRemoteSensing Sensing / Perceiving Analysis Extracting Information / Knowledge Output Subject
- 4. Definitionof RemoteSensing Remote sensing is art, science & technology adopted for obtaining reliable information of the objects on the surface of earth without coming into physical contact. In fact we are measuring and recording the electro- magnetic radiations reflected and emitted by the bodies. Major objective is to Analyze/Understand the Environmental and Natural resources information.
- 5. Componentsof RS Energy Source Radiation Atmosphere Target area Sensor Ground Acquisition centers/ Receivers Interpretation/ Analysis Output to Clients
- 6. Electro MagneticRadiation Sun is the main source of energy. Energy propagates in form of Electro Magnetic Radiation (EMR). Wavelength (λ) Frequency (ν) Velocity (C) c = ν* λ
- 7. ElectroMagneticSpectrum Light energy is explained as EMR and can be classified according to the length of the wave. All possible energy channels called as Electro Magnetic Spectrum (EMS). Human eyes can only measure visible light but sensors can measure other portions of EMS. Figure: Electro Magnetic Spectrum (EMS)
- 9. Sensors Sensors are the devices, which gathers energy and converts it into a signal and presents it in form suitable for obtaining information about the target under investigation (Aggarwal, S. 2003). Types of Sensors ACTIVE - Creates their own energy - Work day & night - Non seasonal Ex: Radar, LIDAR PASSIVE - Depends on External energy, Sun, fire etc - Work on day - Seasonal Ex: Latsat, LISS, Spot & AWIFS
- 11. RADARSAT(Active Sensor) - Canadian Space Agency - Altitude: 798 KM - Inclination: 98.6° - Orbit: Polar - Orbit period: 100.7’ - Revisit time: 14 days Write a brief note on at least two active sensors? Image Credit: http://www.asc-csa.gc.ca
- 12. LISSIII (PassiveSensor) - ISRO - NRSC - Altitude: 817 KM - Inclination: 98.7° - Orbit: Polar - Orbit period: 101.35’ - GSD : 23.5 m - Revisit time: 24 days Write a brief note on at least five passive sensors? Image Credit: NRSC
- 13. Platforms Platforms are the places where the sensors are placed. Depending upon the working environment they are classified as follow: Platforms Fixed Platforms Cherry based Tripod based Moving Platforms Air Borne Balloon Based Aircraft Space Borne Geo Stationary Sun Synchronous
- 14. Type of SpaceBorne Platform Geo Stationary Platform • Faces towards particular portion of earth • 3600 km altitude • West to East rotation • Equatorial Orbit • Angular Coverage 120° • Orbital period 24 Hr. • Ex: INSAT, GSAT, etc … Sun Synchronous Platform • Crosses particular place at same local time • 600 - 900 km altitude • North to South rotation • Polar Orbit • Inclination 80 °/100 ° to Equa. • Orbital Period 100’ (Approx.) • Ex: IRS, LandSat, Spot etc …
- 15. Typesof RemoteSensing Type of RS Depending upon energy source (EMR) Depending upon Sensor Depending upon Platform Optical MicrowaveIR or ThermalX-Ray Active Passive Ground Base Air Borne
- 16. OpticalRemoteSensing • In Optical Remote Sensing, optical sensors detect solar radiation reflected or scattered from the earth, forming images resembling photographs taken by a camera high up in space. • The wavelength region usually extends from (300 nm to 3000 nm) the visible and near infrared (commonly abbreviated as VNIR) to the short-wave infrared (SWIR). • Different materials such as water, soil, vegetation, buildings and roads reflect visible and infrared light in different ways. They have different colours and brightness when seen under the sun. • The interpretation of optical images require the knowledge of the spectral reflectance signatures of the various materials (natural or man-made) covering the surface of the earth.
- 17. ThermalInfrared RemoteSensing • There are also infrared sensors measuring the thermal infrared radiation emitted from the earth, from which the land or sea surface temperature can be derived. • The middle-wave infrared (MWIR) and long-wave infrared (LWIR) are within the thermal infrared region. • The wavelength range of 3000 nm to 5000 nm and 8000 nm to 14000 nm. These radiations are emitted from warm objects such as the Earth's surface. • Thermal Infra RS used for measurements of the earth's land and sea surface temperature and forest fire.
- 18. MicrowaveRemoteSensing These satellites carry their own "flashlight" emitting microwaves to illuminate their targets and Analyzes the information collected by the sensor. The active sensors emit pulses of microwave radiation to illuminate the areas to be imaged. A microwave remote sensor records the backscattered microwaves from earth or sea surface. The Microwave wavelength range of 1 mm to 1 m of electromagnetic spectrum. So, have an additional advantage as they can penetrate clouds. Most of the microwave sensors are active sensors, having there own sources of energy. Thus, images can thus be acquired day and night.
- 19. Characteristicsof Sensors Atmospheric Windows Spectral Resolution Spatial Resolution Radiometric Resolution Temporal Resolution
- 20. AtmosphericWindows The spectral Bands for which the atmosphere is transparent are called as the Atmospheric windows.
- 21. SpectralResolution The ability of a sensor to discriminate b/w different wavelengths in the detected signals. RS sensors can have spectral resolution from more than 1µm to 1 nm. Low Resolution Medium Resolution High Resolution Panchromatic Multi-Spectral (MS) Hyper-Spectral (HS) Single Band >1, <20 bands >= 20 bands CartoSat P5 LISS-III, LandSat AVIRIS, Hyperion
- 22. SpectralResolution Single Band: PAN 500 - 750 nm CartoSat 1: Band F image showing Katraj, Pune Panchromatic Multi-Spectral Hyperion: Image showing Katraj, Pune Four Band: 0.52-0.59 (green) 0.62-0.68 (red) 0.77-0.86 (near IR) 1.55-1.70 (mid-IR)
- 23. SpatialResolution A measure of the smallest distance between two objects that can be distinguished by a sensor. Source: Rees, 1999 Orbview : BVU (1 metre ) LISS III: BVU (23.5 metre ) Image Credit: USGS Image Credit: NRSC
- 24. 0.6 m Spatial Resolution Hyper spectral Space Image
- 25. SpatialResolutionof Satellites Satellites Sensors Optical Radar Spatial resolution LOW MEDIUM HIGH VERY HIGH >2KM 2KM-100M 100M -10M <10M CORONA X X COSMOS TK-350 X X KVR-1000 X X ENVISAT AATSR X X ASAR X X X MERIS X X X ERS AMI-SAR X XATSR X X GOME X X GEOEYE GEOEYE-1 X X IKONOS OSA X X IRSP6/RESOURCESAT LISS-III X X LISS-IV X X AWIFS X X
- 26. SpatialResolutionof Satellites Satellites Sensors Optical Radar Spatial resolution LOW MEDIUM HIGH VERY HIGH >2KM 2KM-100M 100M -10M <10M LANDSAT MSS X X TM X X X ETM+ X X METEOR M-N1 X X X X X METEOSAT MVIRI X X SEVIRI X X GERB X X METOP X X NOAA AVHRR X X ORBVIEW2 SEAWIFS X X QUICKBIRD X X RADARSAT SAR X X X RESURS ESI X X MSU X X X SPOT HRG X X HRS X X HRV X X HRVIR X X X VGT X SRTM X X WORLDVIEW X X
- 27. RadiometricResolution Radiometric resolution is a measure of sensor sensitivity to the magnitude of the EMR. Finer the radiometric resolution greater the ability to detect the small diff. in reflected/ emitted energy. Digital resolution is a synonym to Radiometric resolution. It is the number of bits comprising the each image. It is also referred as no. of brightness levels available to record the energy. Radiometric Resolution 1 bit = 21 = 2 = {0, 1} 8 bit = 28 = 256 = {0,1,……….,255} 10 bit = 210 = 1024 = {0,1,……………………..,1023}
- 28. TemporalResolution Is the revisit time period of sensor to image the same area at the same viewing angle. Multi temporal Remote sensing Kedarnath Floods (June 2013) Pre Post Image Credit: NRSC
- 30. SpectralReflectanceCurve Is the plot between the Spectral reflectance (ratio of reflected energy to incident energy) and wave length. It depends upon the Chemical composition and Physical conditions. Image Credit: Dr Robert Sanderson Typical Spectral reflectance curve for Vegetation, Water & Soil
- 31. How the Objectis IdentifiedbySensor? The Basic principle of Remote Sensing is that each object reflect and emit energy of particular part of EMR in a unique way. Therefore, the signatures received from different objects is always different. This is called its Spectral signature. This is the key for interpretation in RS.
- 32. Whichimagewillbesuitable? Consideration factors are: Purpose – what You are interested in Scale- what will be the scale of out put These will decide Bands – which part of spectrum Spatial Resolution – Positional accuracy required or minimum size of a object to be identified Seasons of data acquisition For Large scale Urban mapping High resolution images are applicable. Example: IRS 1-D PAN 5.8m Cartosat 1 2.5 m Cartosat 2 1m Ikonos PAN 1m Quickbird 0.6m
- 33. ForDisplay: For single band panchromatic: 0 is black and 255 is white and in between gray For RGB: Three value from three band assigned as R,G & B will produce combination of color For example: Red=255, Green=255 & Blue=0, will be Yellow How to displayinyourComputer? Image is supplied in a specific format. Image need to be converted to the S/W specific format. Most of the S/W provide the interface to import such images. Once imported it can be displayed and further processing can be carried out.
- 34. Blue Green Red NIR SWIR Part of spectrum Monitor color guns Viewing images Three bands are viewable simultaneously Band 4 Band 3 Band 2 Band 4 Band 5 Band 3 Band 1 Band 2 Band 3
- 35. Applications of RS Forestry Geology Agriculture Ocean & coastal monitoring Hydrology Pollution monitoring Land use pattern Urban planning Biodiversity conservation Surveying and mapping National Security Environment al Science
- 36. Applicationof RemoteSensing Agricultural Crop type classification. Crop condition assessment. Crop yield estimation. Crop stress monitoring. Crop production forecasting Mapping of soil characteristic. Soil moisture estimation. Ocean applications: Storm forecasting. Water quality monitoring. Aquaculture inventory and monitoring. Navigation routing. Coastal vegetation mapping. Oil spill. Forestry Forest cover and density mapping Deforestation mapping Forest fire mapping. Grassland mapping Shifting cultivation Wetland mapping and monitoring Biomass estimation Species inventory National Security Targeting Disaster mapping and monitoring Damage assessment Weapons monitoring Homeland security Navigation Policy
- 37. Hydrology: Watershed mapping and management Flood delineation and mapping Ground water targeting Assessment of land surface water Assessment of sub surface water Snow melt run-off Multipurpose river valley Land Use/Land Cover mapping: Natural resource management Wildlife protection Encroachment Applicationof RemoteSensing Urban Planning: Land parcel mapping Infrastructure mapping Land use change detection Future urban expansion planning Geology: Lithological mapping Mineral exploration Environmental geology Sedimentation mapping and monitoring Geo-hazard mapping Glacier mapping