Remote Sensing Radar Instructor: Gabriel Parodi Implementation of the Training Strategy of the Monitoring for Environment and Security in Africa (MESA) Programme Remote Sensing Radar Instructor: Gabriel Parodi Date: 01/03/2017 Training Reference: 2017 RSGIS_01 Document Reference: 2017RSGIS_01/PPT/L3 Issue: 2017/L3/3/V2_En Addis Ababa, Ethiopia

Lecturer at University of Twente, ITC   Name Responsibility Contributions from Gabriel Parodi Lecturer at University of Twente, ITC Edited by Tesfaye Korme  Team Leader and Training Manager, Particip GmbH  Reviewed by Martin Gayer  Project Manager, Particip GmbH  Approved by Robert Brown Technical Development Specialist (TDS), TAT

Short Introduction RS Trainer: Mr. Gabriel Parodi Department of Water Resources, Geo-Information Science and Earth Observation (ITC) at the University of Twente, Enschede, The Netherlands. MESA Training Contractor: Particip-ITC-VITO Consortium Consortium partners Particip GmbH www.particip.de Martin Gayer: martin.gayer@particip.de ITC – Faculty of Geo-Information Science and Earth Observation www.itc.nl Chris Mannaerts: c.m.m.mannaerts@utwente.nl VITO – Remote Sensing Unit Applications Team www.vito.be Sven Gilliams: sven.gilliams@vito.be Particip is the main Contractor

Radar Principles of radar remote sensing Lesson i: Title: clarify 1/59 Radar Topics: Principles of radar remote sensing Geometric properties of radar images SAR raw data processing Geometric and radiometric distortions of radar images Basics of SAR interferometry SAR applications more illustrations animation video tutorial tryout formulae more text glossary help

Platform tbd animation more illustrations animation video tutorial Lesson 6.1: Radar: clarify 2/59 Platform tbd animation more illustrations animation video tutorial tryout formulae more text glossary help

The components of a wave Lesson 6.1: Radar: clarify 3/59 Waves tbd The components of a wave animation more illustrations animation video tutorial tryout formulae more text glossary help

Wavelengths Basic principle of radar more illustrations animation Lesson 6.1: Radar: clarify 4/59 Wavelengths Basic principle of radar more illustrations animation video tutorial tryout formulae more text glossary help

Microwave region of spectrum Lesson 6.1: Radar: clarify 5/59 Microwave region of spectrum tbd animation more illustrations animation video tutorial tryout formulae more text glossary help

Radar System tbd animation more illustrations animation video tutorial Lesson 6.1: Radar: clarify 6/59 Radar System tbd animation more illustrations animation video tutorial tryout formulae more text glossary help

Partial penetration of soil/vegetation Lesson 6.1: Radar: clarify 7/59 Advantages of radar All-weather Day and night Sensitive for: geometric shape surface roughness moisture contents Partial penetration of soil/vegetation animation more illustrations animation video tutorial tryout formulae more text glossary help

Radar Image ERS-1 tbd animation more illustrations animation video Lesson 6.1: Radar: clarify 8/59 Radar Image tbd ERS-1 animation more illustrations animation video tutorial tryout formulae more text glossary help

SAR systems Aircraft CCRS Convair 580 JPL AirSAR Others Satellites Lesson 6.1: Radar: clarify 9/59 SAR systems Aircraft CCRS Convair 580 JPL AirSAR Others Satellites Seasat SIR A,B,C ERS-1,2 JERS-1 ALMAZ Radarsat Envisat animation more illustrations animation video tutorial tryout formulae more text glossary help

Electromagnetic Waves Lesson 6.1: Radar: clarify 10/59 Electromagnetic Waves tbd Polarised Micro Wave animation more illustrations animation video tutorial tryout formulae more text glossary help

Imaging Geometry Altitude Nadir Azimuth Range Slant range Near range Lesson 6.1: Radar: clarify 11/59 Imaging Geometry Altitude Nadir Azimuth Range Slant range Near range Far range Swath width Swath length Incidence angle animation more illustrations animation video tutorial tryout formulae more text glossary help

SAR Imaging Geometry tbd animation more illustrations animation video Lesson 6.1: Radar: clarify 12/59 SAR Imaging Geometry tbd animation more illustrations animation video tutorial tryout formulae more text glossary help

Real Aperture Radar (RAR) System Lesson 6.1: Radar: clarify 13/59 Imaging Radar system Real Aperture Radar (RAR) System animation more illustrations animation video tutorial tryout formulae more text glossary help

Radar pulse propagation and reflection Lesson 6.1: Radar: clarify 14/59 Radar pulse propagation and reflection animation more illustrations animation video tutorial tryout formulae more text glossary help

Incidence angle tbd animation more illustrations animation video Lesson 6.1: Radar: clarify 15/59 Incidence angle tbd animation more illustrations animation video tutorial tryout formulae more text glossary help

Lesson 6.1: Radar: clarify 16/59 Spatial resolution In principle the spatial resolution in slant range and azimuth direction are determined by the pulse length and the antenna beam width, respectively. This setup is called Real Aperture Radar (RAR)! animation more illustrations animation video tutorial tryout formulae more text glossary help

Slant range resolution Lesson 6.1: Radar: clarify 17/59 Slant range resolution tbd animation more illustrations animation video tutorial tryout formulae more text glossary help

Slant and ground resolution Lesson 6.1: Radar: clarify 18/59 Slant and ground resolution animation more illustrations animation video tutorial tryout formulae more text glossary help

Azimuth Resolution Ar = l / l * R = ß * R tbd animation Lesson 6.1: Radar: clarify 19/59 Azimuth Resolution tbd Ar = l / l * R = ß * R animation more illustrations animation video tutorial tryout formulae more text glossary help

RAR geometry Different angles tbd animation more illustrations Lesson 6.1: Radar: clarify 20/59 RAR geometry tbd Different angles animation more illustrations animation video tutorial tryout formulae more text glossary help

Synthetic Aperture Radar (SAR) Lesson 6.1: Radar: clarify 21/59 Synthetic Aperture Radar (SAR) tbd SAR principle animation more illustrations animation video tutorial tryout formulae more text glossary help

Distortions in radar images Lesson 6.1: Radar: clarify 22/59 Distortions in radar images Scale distortions Terrain-induced distortions Foreshortening Layover Shadow Radiometric distortions Speckles (reduction) animation more illustrations animation video tutorial tryout formulae more text glossary help

Layover-foreshortening-shadow Lesson 6.1: Radar: clarify 23/59 Relief distortions Layover-foreshortening-shadow animation more illustrations animation video tutorial tryout formulae more text glossary help

Foreshortening animation more illustrations animation video tutorial Lesson 6.1: Radar: clarify 24/59 Foreshortening animation more illustrations animation video tutorial tryout formulae more text glossary help

Layover animation more illustrations animation video tutorial tryout Lesson 6.1: Radar: clarify 25/59 Layover animation more illustrations animation video tutorial tryout formulae more text glossary help

Shadow on Radar animation more illustrations animation video tutorial Lesson 6.1: Radar: clarify 26/59 Shadow on Radar animation more illustrations animation video tutorial tryout formulae more text glossary help

Radiometric Distortions Lesson 6.1: Radar: clarify 27/59 Radiometric Distortions Speckles are caused by the interference of multiple backscattered signals, thus it is a ‘noise’ that degrades the quality of an image. In order to reduce the influence of speckle one option is to use a speckle filter for the image. a) Original Image b) Speckle filtered image animation more illustrations animation video tutorial tryout formulae more text glossary help

Basics to Interpret Radar Images Lesson 6.1: Radar: clarify 28/59 Basics to Interpret Radar Images Surface roughness Complex dielectric constant Surface Orientation Volume scattering Point Objects animation more illustrations animation video tutorial tryout formulae more text glossary help

Reflectance animation more illustrations animation video tutorial Lesson 6.1: Radar: clarify 29/n Reflectance animation more illustrations animation video tutorial tryout formulae more text glossary help

Complex dielectric constant Lesson 6.1: Radar: clarify 30/n Complex dielectric constant The dielectric constant is an electrical property that influences the interaction between the object and the electromagnetic energy. E.g. with increase of soil moisture, the backscatter coefficient also increases, which produces brighter image signatures. Test site at Outlook, Saskatchewan showing potato fields at pre-emergence stage; C - VV airborne radar; A = irrigated field, B = non-irrigated field. (Source: http://www.ccrs.nrcan.gc.ca/ccr) animation more illustrations animation video tutorial tryout formulae more text glossary help

Lesson 6.1: Radar: clarify 31/n Surface Orientation The scattering depends also on the orientation of the objects. Objects will appear bright if their orientation causes that the energy is optimal reflected toward the antenna. animation more illustrations animation video tutorial tryout formulae more text glossary help

Volume scattering animation more illustrations animation video Lesson 6.1: Radar: clarify 32/n Volume scattering animation more illustrations animation video tutorial tryout formulae more text glossary help

Volume Scattering animation more illustrations animation video Lesson 6.1: Radar: clarify 33/59 Volume Scattering animation more illustrations animation video tutorial tryout formulae more text glossary help

Complex volume scattering Lesson 6.1: Radar: clarify 34/59 Complex volume scattering animation more illustrations animation video tutorial tryout formulae more text glossary help

Lesson 6.1: Radar: clarify 35/59 Point Objects Objects can give a very strong backscattering due to a phenomena called ‘corner reflections’. animation more illustrations animation video tutorial tryout formulae more text glossary help

Effects of row structures Lesson 6.1: Radar: clarify 36/59 Effects of row structures animation more illustrations animation video tutorial tryout formulae more text glossary help

Lesson 6.1: Radar: clarify 37/59 Image Generation To generate radar images several options are possible such as: Signal processing Multi-looking Geometric corrections Radiometric Calibration Radiometric Scaling and Enhancement Spatial filtering Data fusion animation more illustrations animation video tutorial tryout formulae more text glossary help

Image Resampling animation more illustrations animation video tutorial Lesson 6.1: Radar: clarify 38/59 Image Resampling animation more illustrations animation video tutorial tryout formulae more text glossary help

Filtering animation more illustrations animation video tutorial tryout Lesson 6.1: Radar: clarify 39/59 Filtering animation more illustrations animation video tutorial tryout formulae more text glossary help

Speckle Filtering Before After animation more illustrations animation Lesson 6.1: Radar: clarify 40/59 Speckle Filtering Before After animation more illustrations animation video tutorial tryout formulae more text glossary help

Multi-temporal colour composites Lesson 6.1: Radar: clarify 41/59 Multi-temporal colour composites Date 1 Date 2 Date 3 animation more illustrations animation video tutorial tryout formulae more text glossary help

Radar interpretation Should take into account mainly ... Lesson 6.1: Radar: clarify 42/59 Radar interpretation Should take into account mainly ... surface roughness moisture content but also system characteristics... polarisation flight direction incidence angle topography wavelength animation more illustrations animation video tutorial tryout formulae more text glossary help

Wind influence (surface roughness) Lesson 6.1: Radar: clarify 43/59 Wind influence (surface roughness) Smooth water surface (rivers) causing low backscatter Rough water surface (rivers) causing relatively high backscatter animation more illustrations animation video tutorial tryout formulae more text glossary help

Polarised images SLAR system Oklahoma Scale 1:160,000 K band (3.2cm) Lesson 6.1: Radar: clarify 44/59 Polarised images SLAR system Oklahoma Scale 1:160,000 K band (3.2cm) HH polarization HV polarization animation more illustrations animation video tutorial tryout formulae more text glossary help

Polarised images California SLAR system Scale 1:75,000 K band Lesson 6.1: Radar: clarify 45/59 Polarised images SLAR system California Scale 1:75,000 K band HH polarization HV polarization animation more illustrations animation video tutorial tryout formulae more text glossary help

Incidence angle W - open water C - clear cut area in the forest Lesson 6.1: Radar: clarify 46/59 Incidence angle W - open water C - clear cut area in the forest S - swamp p - power line R - road F - forest animation more illustrations animation video tutorial tryout formulae more text glossary help

Wavelength (‘band’) influence Lesson 6.1: Radar: clarify 47/59 Wavelength (‘band’) influence A mixture of crops and woodlands X band (3.2 cm) L band (23.5 cm) animation more illustrations animation video tutorial tryout formulae more text glossary help

Spaceborne SAR systems Lesson 6.1: Radar: clarify 48/59 Spaceborne SAR systems Instrument Band Remarks Owner Radarsat C Canada ERS-1 Not operational ESA ERS-2 Envisat-ASAR JERS-1 L Japan SRTM C and X Space shuttle mission NASA ALOS Planned 2005 TerraSAR-X X Planned 2006 Germany animation more illustrations animation video tutorial tryout formulae more text glossary help

RadarSat animation more illustrations animation video tutorial tryout Lesson 6.1: Radar: clarify 49/59 RadarSat animation more illustrations animation video tutorial tryout formulae more text glossary help

Lesson 6.1: Radar: clarify 50/59 Stereo Viewing Radarsat capable of viewing same location from different positions Gives classic stereo capability animation more illustrations animation video tutorial tryout formulae more text glossary help

Spaceborne SAR - Anaglyphs Lesson 6.1: Radar: clarify 51/59 Spaceborne SAR - Anaglyphs animation more illustrations animation video tutorial tryout formulae more text glossary help

Interpretation - applications Lesson 6.1: Radar: clarify 52/59 Interpretation - applications Oil spills Topo & roughness maps Agriculture animation more illustrations animation video tutorial tryout formulae more text glossary help

Classification of multi-temporal ERS Lesson 6.1: Radar: clarify 53/59 Classification of multi-temporal ERS animation more illustrations animation video tutorial tryout formulae more text glossary help

Hydrology applications Lesson 6.1: Radar: clarify 54/59 Hydrology applications Soil moisture Flood extent animation more illustrations animation video tutorial tryout formulae more text glossary help

Forest monitoring: classification Lesson 6.1: Radar: clarify 55/59 Forest monitoring: classification ERS-1 multitemporal,detail ERS-1, time series of 4 segmented images Forest Secondary vegetation Sec. Veg. of Cecropia spp. Pasture Pasture and sec. vegetation Miscellaneous ERS-1, classified time series of 4 segemented images From W. Bijker, 1997 animation more illustrations animation video tutorial tryout formulae more text glossary help

SAR Interferometry (INSAR) Lesson 6.1: Radar: clarify 56/59 SAR Interferometry (INSAR) Examples: Extraction of 3D information of the Earth’s surface Mapping of small surface changes, land subsidence, volcanic eruptions, changes due to earthquakes animation more illustrations animation video tutorial tryout formulae more text glossary help

Shuttle Radar Topography Mission (SRTM) Lesson 6.1: Radar: clarify 57/59 Shuttle Radar Topography Mission (SRTM) Worldwide digital elevation model animation more illustrations animation video tutorial tryout formulae more text glossary help

Land subsidence using INSAR Lesson 6.1: Radar: clarify 58/59 Land subsidence using INSAR Land subsidence often occurs in active mining regions. This example of brown coal open-pit mining west of the city of Cologne, Germany shows an estimate of annual subsidence rates derived from interferometric observations (inset right) using the "permanent scatterer" technique. In this case subsidence rates up to 60 mm/year are observed for extended regions. The subsidence visualized in the image is caused by the lowering of the water-table during mining operation. Source: DLR, http://www.dlr.de/caf/anwendungen/umwelt/erdoberflaeche/ animation more illustrations animation video tutorial tryout formulae more text glossary help

Lesson 6.1: Radar: clarify 59/59 Earthquakes and INSAR This image (Courtesy P. Rosen, JPL) shows the area of the Kobe earthquake imaged by the JERS-1 L-band (25 cm wavelength) radar. The time separation between the two images used to form this interferogram is 2.5 years. The areas of high decorrelation corresponds to the areas of high damage as well as high strain. The phase coherence maps can provide information on the spatial extent of the destruction. (Source: http://www.cacr.caltech.edu/SDA/InSAR/insardesc.html) animation more illustrations animation video tutorial tryout formulae more text glossary help

Learning Activities intro clarify look act reflect assess Lesson 6.1: Radar: clarify 59+1 Learning Activities intro clarify look act reflect assess Check intro for how to continue

Lessons 1. Remote sensing – why? (mandatory) Course: DERS Lessons 1. Remote sensing – why? (mandatory) 2. Electromagnetic energy and remote sensing (mandatory) 3. Sensors and platforms (mandatory) 4. Aerial cameras and photography (mandatory) 5.1 Multispectral scanners: whiskbroom and pushbroom (mandatory) 5.2 Multispectral scanners: earth observation systems (discretionary) i Active sensors: radar (discretionary) 6.2 Active sensors: laser scanning (discretionary) 7. Sub-surface remote sensing (discretionary) 8. Radiometric correction (mandatory) 9. Geometric aspects (mandatory) 10. Image enhancement and visualization (mandatory) 11. Visual image interpretation (mandatory) 12. Digital image classification (mandatory) 13. Thermal remote sensing (discretionary) 14. Imaging spectrometry (discretionary) 15. Final project

Lesson 6.1: Radar Glossary Backscatter: The microwave signal reflected by elements of an illuminated surface in the direction of the radar antenna. Di-electric constant: Parameter that describes the electrical properties of medium. Reflectivity of a surface and penetration of microwaves into the material are determined by this parameter. Foreshortening: Spatial distortion whereby terrain slopes facing the side-looking radar are mapped as having a compressed range scale relative to its appearance if the same terrain was flat. Ground range: Range direction of the side-looking radar image as projected onto the horizontal reference plane. Incidence angle: Angle between the line of sight from the sensor to an element of an imaged scene and a vertical direction to the scene. Interferometry: Computational process that makes use of the interference of two coherent waves. In the case of imaging radar, two different paths for imaging cause phase differences from which an interferogram can be derived.

Lesson 6.1: Radar Glossary Layover: Extreme from of Foreshortening, i.e. relief distortion in imagery, in which the top of the reelecting object (e.g. a mountain) is closer to the radar than the lower part of the object. The image of such a feature appears to have fallen over towards the radar. Range: Line of sight between the radar and each illuminated scatterer. RAR : Acronym for Real Aperture Radar SAR: Acronym for Synthetic Aperture Radar. Slate Range: Image direction as measured along the sequence of line of sight Speckle: Interference of backscattered waves stored in the cells of a radar image. It causes the return signals to be extinguished or amplified resulting in random dark and bright pixels in the image.