Radar Remote Sensing By FalahFakhri Post-doctoral Scholarfalah.firstname.lastname@example.org://www.researchgate.net/profile/Falah_Fakhrihttps://falahfakhri.wordpress.comhttps://twitter.com/FALAHFAKHRI Department of Geography and Geology • Tuesday 26/08/2014 Time: 14:00 – 15:00 MAANTIETEEN JA GEOLOGIAN LAITOS
Seminar’s outline •Passive and active Remote Sensing • Concept of Radar • Concept of SAR • Optical Image Format and Characteristics • SAR Image Format and Characteristics • Amplitude • Phase • Images acquisitions • Software's are used in SAR (Radar Images Processing)
Passive and active Remote Sensing 1/1 • Passive vs. Active Sensors
Concept of Radar (1/10) Echolocation is the use of sound waves and echoes to determine • where objects are in space. • Batsuse echolocation to navigate and find food in the dark. To echolocate, bats send out sound waves from their mouth or nose. When the sound waves hit an object they produce echoes. The echo bounces off the object and returns to the bats ears. Bats listen to the echoes to figure out where the object is, how big it is, and its shape.
Concept of Radar (2/10) Imagine you are in the Grand Valley and you shout. The cliffs will reflect the sound wave. After some time you will hear an echo, which is not exactly the same compared to what you shouted. This is the “principle” of a radar!
Concept of Radar (3/10) RADAR stands for Radio Detection and Ranging … so what is a Radar? A: (Imaging) Radar is an active system that uses a transmitter to illuminate a scene. The pulses sent are microwaves, i.e. a wave with an amplitude and a phase, having a certain frequency and polarization. The radar then records the echo or (backscatters) scattered back from the objects/targets B: Non imaging
Concept of Radar (4/10) MAANTIETEEN JA GEOLOGIAN LAITOS
Concept of Radar (5/10) radars illuminate the target so that they • can operate day and night. • Microwave frequencies Electromagnetic waves penetrate to Some extent through media. • At most frequencies clouds are transparent! • Complexinteraction with medium or target: a “Radar image”is not a photo!
Concept of Radar (6/10)Passive Remote sensing Active Remote Sensing
Concept of Radar (7/10)interaction with medium or targets The transmittedpulse interacts with the Earth surface and only a portion of it is backscattered to the receiving antenna
Concept of Radar (9/10) • Surface Roughness: • Back-scattering increases with roughness • Moisture content : • Back-scattering • increases with moisture • Topography : • Viewing geometry • affects the signal
Concept of SAR (1/1) Synthetic Aperture Radar (SAR) • It has cloud-penetrating capabilities because it uses imaging system (Microwave frequencies Electromagnetic) waves. •It has day and night and weather-independent operational capabilities because it is an active system. •Finally, its ‘interferometric configuration’
Optical Image Format and Characteristics (1/1) Characteristics of Image
SAR Image Format and Characteristics (1/6) Raw data Detected SAR image, Single Look Complex, (SLC)
SAR Image Format and Characteristics (2/6) Amplitude The detected SAR image contains a measurement of the Amplitude (Intensity) of the radiation backscatteredtoward the radar by the objects (scatterers) contained in each SAR resolution cell. Typically, exposed rocks and urban areas show strong amplitude ( bright pixel) whereas smooth flat surface, like quiet water basins show low amplitude (dark pixels) since the Backscatters (radiation) is mainly measured away from the radar.
SAR Image Format and Characteristics (3/6) Phase The pulses (radiation) transmitted from the radar has to reach the scatterers on the ground and then to comeback to the radar in order to form the SAR image. Scatterersat different distance from the radar introduce a different delay between transmission and reception of the radiation.
SAR Image Format and Characteristics (5/6) Descending
SAR Image Format and Characteristics (6/6)Satellite Radar Systems available now and into the future
Software's are used in SAR (Radar Images Processing) (1/6) https://earth.esa.int/web/guest/home
Software's are used in SAR (Radar Images Processing) (2/6) https://earth.esa.int/web/guest/home
Software's are used in SAR (Radar Images Processing) (3/6)NEST (NEW ESA SATELLITE TOOL BOX)
Software's are used in SAR (Radar Images Processing)(4/6)NEST (NEW ESA SATELLITE TOOL BOX)
Software's are used in SAR (Radar Images Processing)(5/6)NEST (NEW ESA SATELLITE TOOL BOX)
Software's are used in SAR (Radar Images Processing)(6/6)GAMMA Remote sensing