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Contents Remote Sensing (RS) Remote Sensing is Fundamentals of Remote Sensing defined as the acquisition – What is Remote Sensi...

Contents Remote Sensing (RS) Remote Sensing is Fundamentals of Remote Sensing defined as the acquisition – What is Remote Sensing of information about an – Brief history of Remote Sensing & Satellite object without being in Earth observation Satellite programs physical contact with it Remote Sensing – Process of Remote Sensing – Needs of spatial data – Advantages of RS – Application of RS Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Remote Sensing What is Remote Sensing The science of satellite remote sensing integrates the understanding, interpretation and establishment of relations between natural phenomena and measurements of electromagnetic energy that is either emitted or reflected from the Earth's surface or its "It is the practice of deriving atmosphere. information about the Earth's surface These measurements are made for a large using images that register reflected or number of locations on the Earth's surface emitted electromagnetic radiation in by sensors onboard spaceborne satellites one or more regions of the spectrum." and are output as imagery. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah The Remote Sensing Process Plan Database Digitizer Scanner Photogrammetry Tabular data Cadastre Land survey/GPS Remote Sensing 7  Remote Sensing Data Satellite Systems GIS integrates a variety of data types from a variety of sources, so it provides multiple data entry options. Communic ation Earth Observation Satellites Satellites Navigation Satellites Satellites Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Satellite Launches Types of Satellites Communication Satellites – To broadcast television, internet, and enable telephone Separation applications. Weather Satellites – To record and monitor the Earth’s climate: temperature, pollution, cloud movement. Satellite Satellite Launch Navigational Satellites – To help aircraft and vessels navigate and determine geographic location. Earth Observation Satellites Satellite – To observe the earth with various sensors, including optical Launch In and radar cameras. Typically used for environmental Orbit monitoring and various mapping applications. Fundamentals of Remote Sensing – S.Sivanantharajah Brief History Brief History of Remote Sensing – Launches of Satellites A key development from 1960 to 1980 was the 1972 – Launch of the first earth resource satellite (Landsat -1) use of multispectral sensors, stimulated in part 1980’s – Landsat-4: new generation of Landsat sensors by the declassification of military satellites that 1986 – Launch of French earth observation satellite (SPOT-1) used both the infrared and microwave bands to 1990’s – Launch of earth resource satellites by national space observe the Earth's surface. agencies and commercial companies Following pioneering research by the U.S. 1990 – Launch of French earth observation satellite (SPOT-2) National Aeronautics and Space Administration (NASA) and the U.S. National Academy of 1992 – National Space Development Agency (NSDA) of Japan – Sciences to assess the utility of Earth JERS1 observation in forestry and agriculture, NASA 1993 – Launch of Landsat -6 failed launched Landsat 1 in 1972 to monitor Earth's 1995 – Launch of Canadian Space Agency Satellite – Radarsat land areas. Fundamentals of Remote Sensing – S.Sivanantharajah Brief History of Remote Sensing (2) - Launches of Satellites Brief History of Remote Sensing (3) - Launches of Satellites 1995 – Launch Indian Remote Sensing Satellite – IRS 1C 2012 - Pleiades 1B, 0.5m 2012 – Launch of French earth observation satellite - SPOT-6 1999 – Launch of Space Imaging Satellite, USA – IKONOS 2013 – Launch of Landsat Data Continuity Mission Landsat 8 1999 – Launch of Landsat 7 2014 – Launch of Digital Globe Satellite – Worldview 3 2014 – Launch of Advanced Land Observing Satellite, Japan- ALOS2 2001 – Launch of Digital Globe Satellite - Quickbird 2014 – Launch of French earth observation satellite - SPOT-7 2002 – Launch of French earth observation satellite - SPOT-5 2014 – Launch of China Earth Observation Satellite – Gaofen 2 2015 - Launch of European Space Agency(ESA) – Sentinel 2A 2005 – Launch Indian Remote Sensing Satellite - Cartosat 1 2016 - Launch of European Space Agency(ESA) – Sentinel 3B 2006 – Launch of Advanced Land Observing Satellite, Japan- ALOS 2016 – Launch of Digital Globe Satellite – Worldview 4 /(GeoEye2) 2017 - Launch of European Space Agency(ESA) – Sentinel 2B 2007 – Launch of Canadian Space Agency Satellite – Radarsat 2 2018 – Launch of China Earth Observation Satellite – Gaofen 11 2007 – Launch of Digital Globe Satellite – Worldview 1 2019 – Launch of ISRO Satellite – Cartosat 3 2021 – Launch of Landsat Data Continuity Mission Landsat 9 2008 – Launch of Space Imaging Satellite, USA – GeoEYE 1 2022 – Launch of ISRO Satellite – EOS-04 2009 – Launch of Digital Globe Satellite – Worldview 2 2023 - Launch of Maxar Satellite - Worldview Legion 1 2024 – Worldview Legion 1 & 2(The next era in Earth intelligence begins at 2011 – Launch of PLEIADES 1 launch – Maxar) Earth Observation Satellites Earth Observation Satellites Japan USA Landsat 9 Operating Europe MAXAR Satellites Ikonos India GeoEye-1 France Quickbird Worldview 1 Worldview 2 Worldview 3 Worldview 4 China Indian Earth Observation Programme First Earth Observation Satellite - Landsat IRS 1A (1988) Level-2 is IRS 1B (1991) IRS P2 (1994) atmospherically IRS 1C (1995) IRS P3 (1996) corrected (Surface IRS 1D (1997) Reflectance) data, IRS P4 (1999) TES (2001) whereas, RESOURCESAT 1 (2003) –IRS P6 CARTOSAT 1 (2005) – IRS P5 Level-1 contains a CARTOSAT 2 (2007) scaled Digital CARTOSAT 2A (2008) Oceansat 2 (2009) Number (DN) ( CARTOSAT 2B (2010) RESOURCESAT 2 (2011) usually 8 or 16 bit RISAT-1 (2013) CARTOSAT 2C (2016) unsigned integers). CARTOSAT 2D (2017) CARTOSAT 3 (2019) Fundamentals of Remote Sensing – S.Sivanantharajah  Main Earth observation Satellites - SPOT WorldView Legion 1 & 2 (USA) To be launched by Elon Musk’s SpaceX WorldView Legion is a constellation of Earth observation satellites built and operated by Maxar. Constellation is planned to consist of 6 satellites in both SPOT 1 launched February 22, 1986 with 10 m & 20. Withdrawn December 31, 1990. polar and mid-inclination orbits, providing 30 cm-class SPOT 2 launched January 22, 1990 and deorbited in July 2009. resolution. SPOT 3 launched September 26, 1993. Stopped functioning November 14, 1997 WorldView Legion Satellite Constellationis the next- SPOT 4 launched March 24, 1998 generation satellite constellation and will provide 30cm SPOT 5 launched May 4, 2002 with 2.5 m, 5 m & 10 m high-resolution satellite imagery. SPOT 6 launched September 9, 2012 with 1.5 m & 8 m The WorldView Legion will be transported in low orbit of SPOT 7 launched June 30, 2014 with 1.5 m & 6 m an altitude of 450km and will have 15 revisits per day. WorldView Legion will support and enable advanced persistent monitoring from sundown to sun up in real time Weather Satellites International Space Station How Sri Lanka look likes What are Sensors Remote Sensing “Remote” Means far away. Remote sensing is the science Remote Sensing means sensing things (and to some extent, art) of from a distance. Of our five sensors we use three as remote sensors when we acquiring information about the Watch a football game from the stands Earth's surface without actually (Sense of sight) being in contact with it. This is Smell freshly baked bread in the oven done by sensing and recording (sense of smell) reflected or emitted energy Hear a telephone ring (sense of hearing) Five Sensors (touch, taste, and processing, analyzing, and sight, smell & hearing) applying that information.  Electromagnetic Radiation What do satellites measure ? Earth-Ocean-Land-Atmosphere System Reflects solar radiation back into space Emits infrared and microwave radiation into space Remote Sensing (RS) Earth observation from space and air Remote Sensing is a technology to observe objects’ size, shape and character without direct contact with them. The reflected or radiated electromagnetic (EM) waves are received by sensors. The characteristics of reflected or radiated EM waves depend on the type or condition of the objects. Process of Remote Sensing (1) Process of Remote Sensing (2) Energy Source or Illumination (A) - Radiation and the Atmosphere (B) - The first requirement for remote sensing is to have As the energy travels from its source to the target, it an energy source (Sun) which illuminates or will come in contact with and interact with the provides electromagnetic energy to the target of atmosphere it passes through. This interaction interest. may take place a second time as the energy travels from the target to the sensor. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Process of Remote Sensing (3) Process of Remote Sensing (4) Interaction with the Target (C) – Recording of Energy by the Sensor (D) - after the Once the energy makes its way to the target through energy has been scattered by, or emitted from the the atmosphere, it interacts with the target target, we require a sensor (remote - not in contact depending on the properties of both the target and with the target) to collect and record the the radiation. electromagnetic radiation. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Process of Remote Sensing (5) Transmission, Reception, and Processing (E) – The energy recorded by the sensor has to be transmitted, often in electronic form, to a receiving and processing station where the data are processed into an image (hardcopy and/or digital). Interpretation and Analysis (F) – The processed image is interpreted, visually and/or Distribution digitally or electronically, to extract information about the target which was illuminated. Receiving station processing Archiving Fundamentals of Remote Sensing – S.Sivanantharajah Process of Remote Sensing (6) Digital Images Application (G) – Remote sensing sensors measure the The final element of the remote sensing earth's surface reflection, in various process is achieved when we apply the wavelengths. information we have been able to extract from The measurements are compiled into grids the imagery about the target in order to better of numbers, the digital images. understand it, reveal some new information, Concept of PIXEL (Picture Element) or assist in solving a particular problem. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Image Bit Depth (Pixel Value) Concept of Digital Image 0 1 2 3 4 5 6 7 1 1 1 1 1 1 1 1 20 21 22 23 24 25 26 27 1 2 4 8 16 32 64 128 255 8-bit : 0  255 (256 Values) Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Image data characteristics Single band image display Image data are stored in a regular grid The histogram is used to obtain optimum format (rows & columns). display of single band images. The single elements are called pixels, an Single band images are normally displayed abbreviation of “picture elements”. using a grey scale. Grey shades of the monitor For each pixel, the measurements are stored typically range from black (value = 0) to white as Digital Number values or DN values. (value = 255). Columns Rows Single 45 Pixel 45 83 DN Value 34 65 56 Visualization of Image Data Remote Sensing – Types of Resolution The histogram describes the distribution of The features of the instruments depend on the purpose for which each was designed, varying the pixel values (Digital Numbers, DN) of that in several aspects. image. In simple terms, these are: A histogram indicates the number of pixels – Spatial Resolution : the minimum size of objects for each value in the range between 0 – 255. distinguishable on the Earth's surface Histogram data can be represented either in – Spectral Resolution : the size of the region of the electromagnetic spectrum sensed tabular form or graphically. Histogram – Radiometric Resolution : the number of digital levels used to express the data collected, and – Temporal Resolution : the intervals between imagery acquisition Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Pixel – the Smallest Unit of an Image The resolution of Satellite Images A digital image is comprised of a two dimensional Spatial Resolution : Smallest spatial area array of individual picture elements – called pixels – arranged in columns in rows. from which information is obtained. This Each pixel represents an area on the Earth’s corresponds to size of a pixel. surface. Images where only large A pixel has an intensity value and a location features are visible are said to address in the 2D image. have coarse or low Spatial Resolution : 30 m Spatial resolution is defined by the size of a pixel resolution. In fine or high resolution images, small objects can be detected. Spatial Resolution : 1 m Fundamentals of Remote Sensing – S.Sivanantharajah Spatial Resolution Spatial resolution and pixel Most remote sensing images are composed of picture elements or pixels, which are the smallest units of an image. Pixels are normally square and represent a certain area on an image. It is important to distinguish between pixel size and spatial resolution. If a sensor has a spatial resolution of 20m and an image from that sensor is displayed at full resolution, each pixel represents an area of 20m X 20m on the ground. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Scale of Image/Map Spectral Resolution The ratio of distance on an image or map, to Spectral Resolution : Sensitivity range of the actual ground distance is referred to as detector defines the spectral differences scale. If you had a map with a scale of which may be observed. 1:100,000 an object of 1 cm length on the Spectral resolution describes the ability of a map would actually be an object 100,000cm sensor to define fine wavelength intervals. (1 Km) long on the ground. The finer the spectral resolution, the Maps or images with small “map to ground narrower the wavelength range for a rations” are referred to as small scale ( eg: particular channel or band. 100,000) and those with larger rations (eg: 5:000 are called large scale. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Temporal Resolution Radiometric Resolution Temporal Resolution: The smallest period (in Pixels describes the spatial structure of an image, the radiometric characteristics describe the actual time) between two images of the same area. information content in an image. This refers to the length of time it takes for a Every time an image is acquired on film or by a satellite to complete one entire orbit cycle sensor, its sensitivity to the magnitude of the electromagnetic energy determines the radiometric (revisit period). resolution. Thus, if a sensor used 8 bits to record the data, there would be 28=256 digital values available, ranging from 0 to 255. Comparing a 2-bit image with an 8-bit image, Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Radiometric Resolution Satellite Images with Spatial Resolution Landsat 7 Image SPOT 5 Image Spatial Resolution : 30 m Spatial Resolution : 10 m Fundamentals of Remote Sensing – S.Sivanantharajah Satellite Images High Resolution Images Spatial IRS 1C ALOS Resolution : 2.5 m Spatial Resolution : Spatial 23.8 m Resolution : 10 m Fundamentals of Remote Sensing – S.Sivanantharajah High Resolution Satellite Imagery (HRSI) Road Map toward HRSI 1986: Spot 10m Pan 10m Characteristics of HRSI 1996: IRS 1C/D 5.8m Pan Mapping capability 1999: IKONOS 1m, (0.82m) 2001: Quickbird 0.6 m High geometric fidelity 2002: SPOT5, 2.5m 2005: Cartosat 1, < 2.5m Highly automated product generation 2006: ALOS, 2.5m Potentially very rapid cycle of image 2007: Cartosat 2, < 1m 2007: Worldview 1, 0.5m collection to customer delivery 2008: Theos, 2m 2008: GeoEYE 1, 0.41m 2009: Worldview2 , 0.46m 2011: PLEIADES 1A, 0.5m 2012: PLEIADES 1B, 0.5m 2013: Skysat 1, 0.9m 2014: Worldview3 , 0.31m 2016: Worldview4 , 0.31m 2019: Cartosat 3, 0.25m Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah 0.25m High Resolution (30cm – 2m) Main Earth observation Satellites IKONOS Quickbird IKONOS - 1999 QUICKBIRD - 2001 https://www.satimagingcorp.com/gallery/ Fundamentals of Remote Sensing – S.Sivanantharajah Satellite Images Peliyagoda Fish Market IKONOS Quickbird Google Images from 2005 to 2010 Spatial Spatial Resolution : Resolution : 1m 60 cm Spatial Resolution : 4m Spatial Resolution : Fundamentals of Remote Sensing – S.Sivanantharajah 2.4 m  PGIS Hambantota Airport Fundamentals of Remote Sensing – S.Sivanantharajah Spatial Data Acquisition About GeoSpatial Data You might be involved in the collection What information do you want? of data, processing of the data, How much detail do you need? analysis of the data or actually using What type of detail? the data for decision making. How frequently do you need this data? In the end, data are acquired to yield information for management purposes: water management, land management, resources management Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Geospatial data acquisition Geospatial data acquisition Do we have the right information Placing geospatial data acquisition in the historical perspective we can take Surveying & available at the right time at the right Mapping as starting point. place to take adequate decisions? About a century ago Photogrammetry evolved as a sub-discipline of Surveying & Mapping offering The awareness increases worldwide an extension to the ground based methods. of the importance of having access to realizable, detailed, timely and The next technological extension was Remote Sensing, which has enabled us to see affordable geospatial data phenomena our eyes cannot see. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Data acquisition Data acquisition … In principle, there are two main categories of Remote sensing methods : which are based Spatial data acquisition on the use of image data acquired by a sensor Ground based methods such as aerial cameras, scanners or a radar. Remote sensing methods Real Sensor Image Observation and Spatial World Data Measurement Database Ground based methods : field observations by performing land surveying Observation and Spatial Real World Measurement Database Need for Spatial Data (1) Need for Spatial Data (2) An agronomist is interested in forecasting the An urban planner needs to identify areas in which overall agricultural production of a large area. This dwellings have been built illegally. The different requires data on the area planted with different types of houses and their configuration need to be crops and data on biomass production to estimate determined. The information should be in a format the yield. that enables integration with other socio-economic information. Satellite Image Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Different type of Houses Need for Spatial Data (3) An engineer needs to determine the optimal configuration for siting of relay stations for a telecommunication company. The optimal configuration primarily depends on the form of the terrain and on the location of obstacles such as buildings. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Need for Spatial Data (4) Automated Building Extraction Landuse Planner is asked to explore AI/ML Automated Building Footprint Extraction and Rooftop Assessment an area and to provide a landuse map By leveraging satellite and aerial/drone imagery, Artificial Intelligence (AI), and Machine Learning (ML) algorithms, it becomes possible to automate of the area. the extraction of building footprints and perform rooftop assessments over large areas, saving time and resources compared to manual ground surveys. Fundamentals of Remote Sensing – S.Sivanantharajah 77 Advantages of remote sensing Image Cost - Analysis Enables to observe a broad area at a time. 12 Hectare (30 Acres) 1 Sq.km US$ 25.00 Enables to observe the area for a long period. 1 Sq.km Rs 9000 – Repeat pass observation (Time series data, Rs. 1080/- 1 Ha 1 Acre Rs. 90 Rs. 36 change detection) 1 Perch Cents 21 650 m Enables us to know the condition without visiting the area. Enables us to know invisible information. 180 m – Sensors for various electromagnetic spectrum (Infrared, Microwave) Global coverage Synoptic view Repeatability Cost Quickbird Images Minimum Order US$ 500 Aerial Photos Space-borne Remote sensing The Traditional form of remote sensing Pro: Pro – Covers large areas – Cost effective – Can be easily customized to – Time efficient meet specfic requirements – Multi-temporal (Easy for Change detection) Con – Multi-sensor, Multi-spectral – Overcomes inaccessibility – Can be expensive – Faster extraction of GIS-ready data – Need a access to plane – Acquisition time of 5 minutes gives equal solar – Time consuming interpretation illumination – Repeat coverage often Con: infrequent – Needs ground verification – Doesn’t offer details – Different Sun angles – Not the best tool for small areas – Needs expert system to extract data Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  User Applications Fields of Application Meteorology Weather forecast Forestry Forest mapping Climate Studies de-/re-forestation Global Change forest fire detection Sources/effects Environmental pollution Hydrology Water balance Studies (Ground) water quality Energy balance Climate Change Agrohydrology Agricultural Landuse development Soil Science Land evaluation Engineering Erosion assessment Soil Mapping Water management Physical Physical Planning Biology/ Vegetation mapping/ Planning Scenario studies Nature monitoring Conservation Vegetation condition assessment Land Topography (DTM) Surveying Spatial Data Models GIS Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Urban & Regional Planning Agriculture Scope Scope Mapping & updation of city/town Crop acreage estimation maps Crop modeling for yield & production Urban sprawl monitoring forecast / estimation Town planning Crop & Orchard monitoring Facility management Benefits GIS database development Benefits Timely availability of crop statistics Better decision support, planning & for decision making & planning Dec 16, 2005, Pre-Frost Jan 12, 2006, Damage Mar 05, 2006, Recovery management Crop growth monitoring Rapid information updation Soil status monitoring Infrastructure development Regular reports regarding total area under cultivation monitoring Spatial information analysis Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Flood Damage to Standing Crops Forestry Scope Pre Flood – 17 July 2006 Post Flood – 09 Aug 2006 Satellite image based forest resource mapping and updation Muhro Mari Muhro Mari Forest change detection Darapur Darapur Kot Shahgarch Kot Shahgarch 10098 acr Forest resource inventory Godhpur Godhpur GIS database development Phulani Phulani Than Lake Than Lake Benefits Goth Lataran Shahpur Goth Lataran Availability of baseline information Shahpur Ural Ural Junno Dhand Junno Dhand Planning for aforestation strategies Futuristic resource planning Goth Raza Mahar Goth Raza Mahar Goth Azizpur Goth Azizpur Sustainability of environment Wild life conservation & development for 3516 acr recreation purpose Fundamentals of Remote Sensing – S.Sivanantharajah  Coast Resource Mapping Landuse / Landcover Mapping Scope Scope Mangrove forest monitoring Monitoring dynamic changes Change detection Urban/Rural infrastructure Hazard impacts Waterlogging & salinity Aqua-culture zones Benefits Benefits Assessment of spatial distribution of Availability of updated information land resources on mangroves forest Infrastructure monitoring Planning strategies for aforestation Availability of usable land and deforestation trend Future planning for better land Timely Intervention in specific areas management for socio-economic as and when needed Satellite image Mangroves forest map development Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Extracting information about vegetation categories Sea Surface Temperature It is possible to roughly assess distribution of various kinds of vegetation. Sea Surface Temp distribution of chlorophyll However, detailed identification of tree types is difficult. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Characterizing Satellites and Sensors Satellite Orbit Orbits Orbit : The path followed by a – Polar vs. Geostationary satellite is referred to as its orbit. Energy Sources Orbit selection can vary in terms – Passive vs. Active of altitude (their height above the Solar and Terrestrial Spectra Earth's surface) and their – Visible, UV, IR, Microwave… orientation and rotation relative to Measurement Techniques the Earth. – Scanning, Non-Scanning, Imager, Sounders... Many remote sensing platforms Resolution (Spatial, Temporal, Spectral, Radiometric) are designed to follow an orbit – Low vs. High (basically north-south) which, in Applications conjunction with the Earth's – Weather, Land Mapping, Atmospheric Physics, Atmospheric rotation (west-east), allows them Chemistry, Air Quality. to cover most of the Earth's surface over a certain period of time. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Polar Orbit Satellite Referencing Scheme It is unique for each satellite mission Fixed, circular orbit above Earth. For conveniently identifying the geographic Sun synchronous orbit ~400 - 1,000 km location of points on the earth. This scheme is designated by Path and above Earth with orbital passes are at Rows and its concept is based on the nominal orbital characteristics. about the same local solar time each Path day. – An orbit is the course of motion taken by the satellite in space and the ground trace of the orbit is called a 'Path’. Row – The lines joining the corresponding scene centers of different paths are parallel to the equator and are called ‘Rows’. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Geostationary Orbit Sun-synchronous Has the same rotational period as Earth Many of these satellite orbits are also Appears ‘fixed’ above Earth sun-synchronous such that they cover Orbits ~36,000 km above the equator each area of the world at a constant Weather and communications satellites local time of day called local sun time. commonly have these types of orbits. This ensures consistent illumination conditions when acquiring images in a specific season over successive years, or over a particular area over a series of days. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Swath Classification of Sensors As a satellite revolves around the Earth, the A sensor is a device that measures sensor "sees" a certain portion of the Earth's and records electromagnetic surface. The area imaged on the surface, is energy. referred to as the swath. Sensors can be divided into two The satellite's orbit and the rotation of the groups Earth work together to allow complete – Passive Sensors : Passive sensors coverage of the Earth's surface. depend on an external source of energy, usually the Sun. – Active Sensors : Active sensors have their own source of energy. Active sensors include the laser altimeter and radar. Fundamentals of Remote Sensing – S.Sivanantharajah  Passive Remote Sensing Active Remote Sensing An active sensor emits radiation which is directed toward The Sun provides a very convenient the target to be investigated. The radiation reflected from source of energy for RS. the target is detected and measured by the sensor. Advantages for active sensors: The Sun’s energy is reflected for visible – The ability to obtain measurement anytime. Regardless of the time of the day, season or weather. wavelengths, or absorbed and then re- – Examine wavelengths that are not sufficiently provided by the Sun. (e.g. microwaves) emitted for thermal IR wavelength. – To better control the way that a target is illuminated. However, active systems require the generation of a fairly For all reflected energy, this can only large amount of energy to adequately illuminate the targets. take place during the time when the sun is illuminating the earth. Platforms Platforms are: Ground based Airborne Spaceborne Sensing from 1 meter to 36,000 km height Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Platforms Airborne In Remote Sensing, the sensor is Aerial platforms are primarily stable wing mounted on a platform. aircraft, although helicopters are – Airborne : Airborne observations are carried occasionally used. out using aircraft with specific modification to Aircraft are often used to collect very carry sensors. detailed images and facilitate the collection – Airborne observations are possible from of data over virtually any portion of the 100m up to 30-40 km height. Earth’s surface at any time. – Spaceborne : Spaceborne remote sensing, satellites are used. Satellites are positioned in orbits between 150 – 36,000 km altitude. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Spaceborne Remote Sensing Platforms In space, remote sensing is conducted Platform Altitude(km) commonly from satellites. Man made satellites include those Geostationary Sat. 36,000 platforms launched for remote sensing, Earth Observation sat. 400 – 1000 communication and telemetry (location & navigation) purposes. Space shuttle 240 – 350 Because of their orbits, satellites permit Airplane 0.3 – 7.5 repetitive coverage of the Earth’s surface on a continuing basis. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Ground Receiving Station (GRS) Ground Receiving Station (GRS).. Contd.. A GRS consists of: Data Acquisition System (DAS) Provides capability to track and receive from satellite using Data Acquisition System X/S band and a auto tracking system. The raw data received (DAS) are stored on high density digital tapes (HDDT) and sent to DPS. Data Processing System Data Processing System (DPS) (DPS) Keeps an inventory of each satellite pass with quality Data Archive Centre (DAC) assessment and catalog archival and by reading the raw data from HDDT, correct them for geometric and radiometric distortions. Data Archive Center (DAC) Offers a catalogue interrogation system and image processing capabilities through an image processing system. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah There are three main options for transmitting Ground Receiving Station Products data acquired by satellites to the surface: Level 0 Uncorrected (raw data). The data can be directly transmitted to Earth if a Ground Receiving Station (GRS) is in the line of Level 1 Radiometrically corrected and sight of the satellite (A). Geometrically corrected only for earth rotation If this is not the case, the data can be recorded on board the satellite (B) for transmission to a (Browse product). GRS at a later time. Data can also be relayed to the GRS through Level 2 Both radiometrically corrected and the Tracking and Data Relay Satellite System Geometrically corrected (Standard product). (TDRSS) (C), which consists of a series of communications satellites in geosynchronous Level 3 Special processing like merging, orbit The data are transmitted from one satellite to enhancement etc. after level 2 corrections another until they reach the appropriate GRS. (Special product). Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Data dissemination Earth observation Satellites The data are recorded on Digital Linear Tapes (DLTs) or More than 150 Earth-observation satellites are CDROMs, DVDs depending on the mission and archived for currently in orbit, carrying sensors that providing data products to users as and when orders are measure different sections of the visible, received. infrared and microwave regions of the Single band data is provided in B/W such as PAN data or electromagnetic spectrum. one band data from multi-spectral sensors. Photographic, The majority of Earth-observation satellites color products called as False Color Composites (FCC) can carry "passive" sensors, measuring either be provided for multi-spectral data. The output scale for prints reflected solar radiation or emitted thermal can vary from 1:1 M to 1:5000. energy from the Earth's surface or atmosphere. Newer satellites also employ "active" sensors that emit energy and record the reflected or backscattered response, from which information about the Earth can be inferred. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Three types of Remote Sensing Moreover, the number of regions of the spectrum for which data are collected, the time taken to revisit the same area of the Earth, the spatial extent of images produced, and whether the satellite's orbit follows the Sun-illuminated section of the Earth (Sun synchronous) or remains over a fixed point on the Earth (geostationary) all vary between satellites and their sensors. The development of satellites over the past 50 years has also been in step with increasing computing capabilities. As data storage capacities and processing speeds increase, so has the ability of Earth-observation satellites to capture, process and Optical Microwave return information. Visible Reflectance Microwave Radiation Near Infrared Reflectance Backscatter Thermal Infrared Thermal Radiation Fundamentals of Remote Sensing – S.Sivanantharajah Electromagnetic Radiation Electromagnetic radiation Two characteristics of electromagnetic radiation are particularly important for understanding remote sensing. These are wavelength & frequency. The wavelength is the length of one wave Energy source to illuminate the target. cycle, usually represented by the Greek Electromagnetic radiation consists of an electrical letter lambda (). Wavelength is measured in meters (m) or some factor of meters such as field (E) which varies in magnitude in a direction nanometers (nm, 10-9 m), micrometers (m, perpendicular to the direction in which the radiation 10-6 m) or centimeters (cm, 10-2 m). Frequency refers to the number of cycles is traveling, and a magnetic field (M) oriented at of a wave passing a fixed point per unit of right angles to the electrical field. Both these fields time. Frequency is normally measured in hertz (Hz), equivalent to one cycle per travel at the speed of light (c). second, and various multiples of hertz. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Electromagnetic (EM) Spectrum Spectrum region used in Remote Sensing Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah The visible spectrum Infrared portion Covers the wavelength range from The light which our eyes - approximately 0.7 μm to 100 μm. our "remote sensors“ can Reflected IR region (0.7 μm to 3.0 detect. μm) is used for remote sensing Note how small the visible purposes in ways very similar to portion is relative to the rest radiation in the visible portion. of the spectrum. The thermal IR region (3.0 μm to 100 μm ) is quite different than the visible The visible wavelengths and reflected IR portions, as this cover a range from energy is essentially the radiation that Violet: 0.400 - 0.446 μm approximately 0.4 to 0.7 is emitted from the Earth‘s surface in Blue: 0.446 - 0.500 μm Green: 0.500 - 0.578 μm μm. the form of heat. Yellow: 0.578 - 0.592 μm Orange: 0.592 - 0.620 μm Red: 0.620 - 0.700 μm Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah Microwave region Bands of Landsat 7 & 8 The microwave region (1 mm to 1 m) covers the longest wavelengths used for remote sensing. For Earth observation, most systems using microwaves are active systems, not depending on the lighting. Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Bands of Landsat 7, 8 & 9 Optical Remote Sensing ETM – Enhance Thematic Mapper OLI - Operational Land Imager TIRS - Thermal Infrared Sensor Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah What is scanner Multispectral Scanner These transform electromagnetic Multispectral Scanners (MSS) mounted on air- or radiation into electrons or other space borne platforms mainly used to measures the reflected sunlight in the optical domain. detectable signals to convey the Measurements can be made for different portions of measurement information of the the Electromagnetic spectrum. viewed scene. MSS have a range from 0.3 to 14 µm. Images stored in two modes Detectors translate incident – Panchromatic Image : operating in visible & near infra red region. radiation levels into so called Digital – Multispectral Images: obtain image data in bands of Numbers (DN). visible, Near IR & Middle IR region Multispectral data Multi Spectral Remotely Sensed Image Digital Images of an area captured in different spectral ranges (bands) by sensors onboard a remote sensing satellite. Band 1 Band 2 Band 3 Band 4 0.45 - 0.52 m 0.52 – 0.59 m 0.62- 0.68 m 0.77 – 0.86 m Fundamentals of Remote Sensing – S.Sivanantharajah Band 1 Visible & Reflective IR Remote Sensing Band 2 Band 3 Band 4 Landsat Images Landsat 5 Frames LANDSAT-7 is equipped with Enhanced Thematic Mapper Plus (ETM+), Images Path 141 Row 56 in two modes Panchromatic Image : operating in visible & near infra red region.(15m Resolution) Multispectral Images: obtain image data in 7 bands of visible, Near IR & Middle IR region. (30 m Resolution) Fundamentals of Remote Sensing – S.Sivanantharajah Landsat Images LANDSAT 7 ETM+ LANDSAT-7 is equipped with Enhanced Thematic Mapper Plus (ETM+), the Band2 Band3 successor of TM. Band1 The observation bands are essentially the same seven bands as TM, and the newly added panchromatic band 8, with a high resolution of 15m was added. Band4 Band5 Band7 Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Landsat 7 Principles applications of Landsat 7 Bands Band TM Wavelength(m) Main Application for TM Data 1 0.45 – 0.52 Coastal water mapping, Soil/Vegetation discrimination and forest mapping. 2 0.52 – 0.6 Green reflectance by healthy vegetation 3 0.63 – 0.69 Chlorophyll absorption for plant species differentiation. 4 0.76 – 0.9 Biomass surveys and delineating water bodies 5 1.55 – 1.75 Vegetation moisture. Snow/Cloud discrimination. 6 10.4 – 11.7 Thermal mapping. Vegetation stress. Soil moisture discrimination. 7 2.08 – 2.35 Vegetation moisture. Fundamentals of Remote Sensing – S.Sivanantharajah Geological mapping. Principles applications of Landsat 8 Bands Sensor Platform characteristics Spectral resolution = part of the EM spectrum measured Radiometric resolution = smallest differences in energy that can be measured Spatial resolution = smallest unit area measured Temporal resolution (Revisit time) = time between two successive image acquisitions over the same area Fundamentals of Remote Sensing – S.Sivanantharajah Spectral Resolution Radiometric Resolution Remotely Sensed Data Spatial Resolution 8- bits 2- bits Temporal Resolution Landsat Aerial Camera Multispectral Satellite Radar Satellite Hyperspectral Sensor IKONOS Hyperion Landsat/Ikonos/Quickbird Fundamentals of Remote Sensing – S.Sivanantharajah Fundamentals of Remote Sensing – S.Sivanantharajah  Satellite Data In Remote Sensing , an image refers to any pictorial representation, regardless of what wavelengths or remote sensing device has been used to detect and record the electromagnetic energy Photograph refers specifically to images that have been detected as well as recorded on photographic film.. Fundamentals of Remote Sensing Fundamentals of Remote Sensing Image Data Characteristics What is scanner Scanners are made by electro-optical devices It is more than a picture known as “solid state detectors”. It contain measurements of EM energy These transform electromagnetic radiation into electrons or other detectable signals to convey the Regular Grid Format. (Rows &Columns) measurement information of the viewed scene. Smallest unit is pixel Detectors translate incident radiation levels into so Each pixel contain a digital Number called Digital Numbers (DN). Detector materials such as photoconductors, Typically for each wave length band measured , a separate „layer‟ is stored photodiodes, charge –coupled devices (CCD). Fundamentals of Remote Sensing Fundamentals of Remote Sensing Multispectral Scanner Pushbroom scanners The pushbroom sensors use linear array Applications of multispectral scanner CCDs composed of thousands of equally data are mainly in the mapping of spaced detectors. Each position(pixel) in landcover, vegetation, surface the line has its own detector. mineralogy and surface water. This recording one entire line at the time. Two types of multispectral scanners can This is called along track scanner. be distinguished, the pushbroom Which are pushed along in the flight track scanner and the whiskbroom scanner. direction. Eq. SPOT1-2-3/HRV, IKONOS Fundamentals of Remote Sensing Fundamentals of Remote Sensing  Whiskbroom Scanner Remote Sensing Data from Satellites A combination of a single detector plus a rotating mirror can be arranged in such a way that the detector „beam‟ will sweep a straight line over the Earth across the track of the satellite at each rotation of the mirror. – This is also called “across track scanner” – The earth‟s surface is scanned line by line as the satellite moves forward. – Eg. Landsat/TM, IRS/LISS, NOAA Fundamentals of Remote Sensing Comparison between sensors Landsat 7 System Landsat - 7 Orbit 705 km, Sun-