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GEOGG141/ GEOG3051Principles & Practice of Remote Sensing (PPRS)Introduction, EM Radiation (i)Dr. Mathias (Mat) DisneyUCL GeographyOffice: 113, Pearson BuildingTel: 7679 0592Email: mdisney@ucl.geog.ac.ukhttp://www2.geog.ucl.ac.uk/~mdisney/teaching/GEOGG141/GEOGG141.htmlhttp://www2.geog.ucl.ac.uk/~mdisney/teaching/3051/GEOG3051.html UCL DEPARTMENT OF GEOGRAPHYUCL DEPARTMENT OF GEOGRAPHY

UCL DEPARTMENT OF GEOGRAPHY

Components (GEOGG141 & GEOG3051)Radiometric principles (Disney)Understanding what we CAN measure and how (& what we cant!)Radiative transfer (GEOGG141 only)Resolution, sampling and practical tradeoffsPre-processing and ground segmentActive remote sensing (LIDAR, RADAR)Applications

2Format

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Remote Sensing at UCLNERC National Centre for Earth Observation (NCEO) http://www.nceo.ac.uk/) Cryosphere @ Earth Sciences: http://www.cpom.org/Carbon Theme @ Geography (Lewis, Mat et al.), NASA MODIS BRDF/albedo and burned are products, ESAMore generallyMSSL: http://www.ucl.ac.uk/mssl e.g. imaging (Muller), planetary, astro, instruments, RADAR, albedo (eg www.globalbedo.org )London?Prof. Martin Wooster @ KCL Geography: NCEO, fire radiative power, atmosphere, urbanImperial: Dr. Liu, Dr. Mason, geoscience, mineral mapping; Prof. Jo Haigh atmospheric, solar variabilityUK prof. body - Remote Sensing and Photogrammetry Societyhttp://www.rspsoc.org/

3Miscellaneous

UCL DEPARTMENT OF GEOGRAPHY3Reading and browsingRemote sensingCampbell, J. B. (2006) Introduction to Remote Sensing (4th ed), London:Taylor and Francis.Harris, R. (1987) "Satellite Remote Sensing, An Introduction", Routledge & Kegan Paul.Jensen, J. R. (2006, 2nd ed) Remote Sensing of the Environment: An Earth Resource Perspective, Prentice Hall, New Jersey. (Excellent on RS but no image processing).Jensen, J. R. (2005, 3rd ed.) Introductory Digital Image Processing, Prentice Hall, New Jersey. (Companion to above) BUT some available online at http://www.cla.sc.edu/geog/rslab/751/index.html Jones, H. and Vaughan, R. (2010, paperback) Remote Sensing of Vegetation: Principles, Techniques, and Applications, OUP, Oxford. Excellent.Lillesand, T. M., Kiefer, R. W. and Chipman, J. W. (2004, 5th ed.) Remote Sensing and Image Interpretation, John Wiley, New York.Mather, P. M. (2004) Computer Processing of Remotelysensed Images, 3rdEdition. John Wiley and Sons, Chichester.Rees, W. G. (2001, 2nd ed.). Physical Principles of Remote Sensing, Cambridge Univ. Press.Warner, T. A., Nellis, M. D. and Foody, G. M. eds. (2009) The SAGE Handbook of Remote Sensing (Hardcover). Limited depth, but very wide-ranging excellent reference book.GeneralMonteith, J. L. and Unsworth, M. H. (1990) Principles of Environmental Physics, 2nd ed. Edward Arnold, London.Hilborn, R. and Mangel, M. (1997) The Ecological Detective: Confronting models with data, Monographs in population biology 28, Princeton University Press, New Jersey, USA.4

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Moodle & www.geog.ucl.ac.uk/~mdisney/pprs.htmlWebTutorialshttp://rst.gsfc.nasa.gov/http://earth.esa.int/applications/data_util/SARDOCS/spaceborne/Radar_Courses/http://www.crisp.nus.edu.sg/~research/tutorial/image.htmhttp://ccrs.nrcan.gc.ca/resource/index_e.php#tutorhttp://octopus.gma.org/surfing/satellites/index.html

Glossary : http://ccrs.nrcan.gc.ca/glossary/index_e.php

NASA www.nasa.govNASAs Visible Earth (source of data): http://visibleearth.nasa.gov/European Space Agency earth.esa.int (eg Image of the week.)NOAA www.noaa.gov5BrowsingSkyBox: https://www.youtube.com/watch?v=aW1-ZWencvA

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General introduction to remote sensing (RS), Earth Observation (EO).......definitions of RSConcepts and termsremote sensing process, end-to-endRadiation IConcepts and termsremote sensing process, end-to-end

6Today

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The Experts say "Remote Sensing (RS) is...The science technology and art of obtaining information about objects or phenomena from a distance (i.e. without being in physical contact with themhttp://ccrs.nrcan.gc.ca/glossary/index_e.php?id=486

But not the whole story:Tend to use Earth Observation (EO). To distinguish from?Domains (atmosphere, terrestrial, ocean, cryosphere, biosphere etc)But also astronomy, planetary remote sensing etc.

7What is remote sensing?

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The not so experts say "Remote Sensing is...Advanced colouring-in.Seeing what can't be seen, then convincing someone that you're right.Being as far away from your object of study as possible and getting the computer to handle the numbers.Legitimised voyeurism(more of the same from http://www.ccrs.nrcan.gc.ca/ccrs/eduref/misc)8What is remote sensing (II)?

UCL DEPARTMENT OF GEOGRAPHY8Remote Sensing Examples9Kites (still used!) Panorama of San Francisco, 1906.Up to 9 large kites used to carry camera weighing 23kg.

UCL DEPARTMENT OF GEOGRAPHYRemote Sensing: scales and platforms10Both taken via kite aerial photographyhttp://arch.ced.berkeley.edu/kap/kaptoc.htmlhttp://activetectonics.la.asu.edu/Fires_and_Floods/

UCL DEPARTMENT OF GEOGRAPHYRemote Sensing: scales and platforms11Platform depends on applicationWhat information do we want?How much detail?What type of detail?

upscalehttp://www-imk.fzk.de:8080/imk2/mipas-b/mipas-b.htm

upscaleupscale

UCL DEPARTMENT OF GEOGRAPHYRemote Sensing: scales and platforms12Many types of satelliteDifferent orbits, instruments, applications

upscale

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UCL DEPARTMENT OF GEOGRAPHY13Brazil 2014Caxiuaa drought experiment, Para StateTLS transect: 100 m along plot, 5m deep 41 million points. 1ha ~0.5Bn points (0.5TB data)

Brazil 2014

UCL DEPARTMENT OF GEOGRAPHYAlso shows zoom in of crown showing we can pick up even quite small branches well and the registration is looking seriously good!14Brazil 2014Caxiuaa drought experiment, Para State

UCL DEPARTMENT OF GEOGRAPHY376 scan locations, several (many!) TB of dataWytham Woods 2015: 6 ha of woodland

UCL DEPARTMENT OF GEOGRAPHYAlso shows zoom in of crown showing we can pick up even quite small branches well and the registration is looking seriously good!16376 scan locations, several (many!) TB of dataWytham Woods 2015: 6 ha of woodland

UCL DEPARTMENT OF GEOGRAPHYAlso shows zoom in of crown showing we can pick up even quite small branches well and the registration is looking seriously good!17

Opportunistic scanning

Trunk diameter?

UCL DEPARTMENT OF GEOGRAPHY18Remote Sensing Examples19Global maps of vegetation from MODIS instrument

IKONOS-2 image of Venicehttp://www.esa.int/esaEO/SEM44R0UDSG_index_1.html

UCL DEPARTMENT OF GEOGRAPHYRemote Sensing Examples20

http://content.satimagingcorp.com/static/galleryimages/geoeye-1-olympic-stadium.jpg

UCL DEPARTMENT OF GEOGRAPHYWhy do we use remote sensing?Many monitoring issues global or regionalDrawbacks of in situ measurement ..Remote sensing can provide (not always!) Global coverageRange of spatial resolutionsTemporal coverage (repeat viewing)Spectral information (wavelength)Angular information (different view angles)21

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source of spatial and temporal information (land surface, oceans, atmosphere, ice)monitor and develop understanding of environment (measurement and modelling)information can be accurate, timely, consistent remote access some historical data (1960s/70s+) move to quantitative RS e.g. data for climatesome commercial applications (growing?) e.g. weathertypically (geo)'physical' information but information widely used (surrogate - tsetse fly mapping) derive data (raster) for input to GIS (land cover, temperature etc.) 22Why do we study/use remote sensing?

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Collection of dataSome type of remotely measured signalElectromagnetic radiation of some formTransformation of signal into something usefulInformation extractionUse of information to answer a question or confirm/contradict a hypothesis 23EO process in summary.....

The bad news (Disney, 2014)

The bad news (Disney, 2014)

UCL DEPARTMENT OF GEOGRAPHY23The Remote Sensing ProcessCollection of information about an object without coming into physical contact with that object24

Passive: solar reflected/emittedActive:RADAR (backscattered); LiDAR (reflected)

UCL DEPARTMENT OF GEOGRAPHYThe Remote Sensing ProcessWhat are we collecting?Electromagnetic radiation (EMR)What is the source?Solar radiationpassive reflected (vis/NIR), emitted (thermal)OR artificial sourceactive - RADAR, LiDAR even sonarNote various pathsSource to sensor direct?Source to surface to sensorSensor can also be source25

UCL DEPARTMENT OF GEOGRAPHYEnergy transportConductiontransfer of molecular kinetic (motion) energy due to contactheat energy moves from T1 to T2 where T1 > T2Convectionmovement of hot material from one place to anothere.g. Hot air risesRadiationresults whenever an electrical charge is acceleratedpropagates via EM waves, through vacuum & over long distances hence of interest for remote sensing26

UCL DEPARTMENT OF GEOGRAPHY26Electromagnetic radiation: wave model27James Clerk Maxwell (1831-1879)Wave model of EM energyUnified theories of electricity and magnetism (via Newton, Faraday, Kelvin, Ampre etc.)Oscillating electric charge produces magnetic field (and vice versa)Can be described by 4 simple (ish) differential equationsCalculated speed of EM wave in a vacuum

UCL DEPARTMENT OF GEOGRAPHYElectromagnetic radiation28

EM wave isElectric field (E) perpendicular to magnetic field (M) Travels at velocity, c (3x108 ms-1, in a vacuum)Or does it?? CERN 2011 .

UCL DEPARTMENT OF GEOGRAPHYWave: terms29All waves characterised by:Wavelength, (m)Amplitude, a (m)Velocity, v (m/s)Frequency, f (s-1 or Hz)Sometimes period, T (time for one oscillation i.e. 1/f)

UCL DEPARTMENT OF GEOGRAPHYWave: terms30Velocity, frequency and wavelength related by

f proportional to 1/ (constant of proportionality is wave velocity, v i.e.

UCL DEPARTMENT OF GEOGRAPHYWave: terms31

Note angles in radians (rad)360 = 2 rad, so 1 rad = 360/2 = 57.3Rad to deg. (*180/) and deg. to rad (* /180)

UCL DEPARTMENT OF GEOGRAPHYEM Spectrum32EM SpectrumContinuous range of EM radiationFrom very short wavelengths ( m , n < 4

UCL DEPARTMENT OF GEOGRAPHYPeak of emitted radiation: Wiens Law44Wien deduced from thermodynamic principles that energy per unit wavelength E() is function of T and At what m is maximum radiant energy emitted?Comparing blackbodies at different T, note mT is constant, k = 2897mK i.e. m = k/Tm, sun = 0.48mm, Earth = 9.66m

UCL DEPARTMENT OF GEOGRAPHYWiens Law45AKA Wiens Displacement LawIncrease (displacement) in m as T reducesStraight line in log-log space

Increasing , lower energy

UCL DEPARTMENT OF GEOGRAPHYParticle model of radiation46Hooke (1668) proposed wave theory of light propagation (EMR) (Huygens, Euler, Young, Fresnel)Newton (~1700) proposed corpuscular theory of light (after al-Haytham, Avicenna ~11th C, Gassendi ~ early17th C)observation of light separating into spectrumEinstein explained photoelectric effect by proposing photon theory of light Photons: individual packets (quanta) of energy possessing energy and momentumLight has both wave- and particle-like propertiesWave-particle duality

UCL DEPARTMENT OF GEOGRAPHYParticle model of radiation47EMR intimately related to atomic structure and energyAtom: +ve charged nucleus (protons +neutrons) & -ve charged electrons bound in orbitsElectron orbits are fixed at certain levels, each level corresponding to a particular electron energyChange of orbit either requires energy (work done), or releases energyMinimum energy required to move electron up a full energy level (cant have shift of 1/2 an energy level)Once shifted to higher energy state, atom is excited, and possesses potential energyReleased as electron falls back to lower energy level

UCL DEPARTMENT OF GEOGRAPHYParticle model of radiation48As electron falls back, quantum of EMR (photons) emittedelectron energy levels are unevenly spaced and characteristic of a particular element (basis of spectroscopy)Bohr and Planck recognised discrete nature of transitionsRelationship between frequency of radiation (wave theory) of emitted photon (particle theory)

E is energy of a quantum in Joules (J); h is Planck constant (6.626x10-34Js) and f is frequency of radiation

UCL DEPARTMENT OF GEOGRAPHYParticle model of radiation49If we remember that velocity v = f and in this case v is actually c, speed of light then Energy of emitted radiation is inversely proportional to longer (larger) == lower energyshorter (smaller) == higher energyImplication for remote sensing: harder to detect longer radiation (thermal for e.g.) as it has lower energy

UCL DEPARTMENT OF GEOGRAPHYPlancks Law50Explains/predicts shape of blackbody curveUse to predict how much energy lies between given Crucial for remote sensing

http://hyperphysics.phy-astr.gsu.edu/hbase/bbrc.html#c1

UCL DEPARTMENT OF GEOGRAPHYConsequences of Plancks Law: plant pigments51Chlorophyll a,b absorption spectraPhotosynthetic pigmentsDriver of (nearly) all life on Earth!Source of all fossil fuel

UCL DEPARTMENT OF GEOGRAPHYConsequences of Plancks Law: human vision52

http://www.photo.net/photo/edscott/vis00010.htmCones: selective sensitivityRods : monochromatic sensitivity

UCL DEPARTMENT OF GEOGRAPHYApplications of Plancks Law53Fractional energy from 0 to i.e. F0? Integrate Planck functionNote Eb(,T), emissive power of bbody at , is function of product T only, so....

Radiant energy from 0 to Total radiant energy for = 0 to =

UCL DEPARTMENT OF GEOGRAPHYApplications of Plancks Law: example54Q: what fraction of the total power radiated by a black body at 5770 K fall, in the UV (0 < 0.38m)?Need table of integral values of F0So, T = 0.38m * 5770K = 2193mKOr 2.193x103 mK i.e. between 2 and 3Interpolate between F0 (2x103) and F0 (3x103)lT (mmK x103)F0l(lT)(dimensionless)2.0673.2734.4815.6346.7388.85610.91412.94514.96316.97418.98120.986

Finally, F00.38 =0.193*(0.273-0.067)+0.067=0.11i.e. ~11% of total solar energy lies in UV between 0 and 0.38 m

UCL DEPARTMENT OF GEOGRAPHYApplications of Plancks Law: exercise55Show that ~38% of total energy radiated by the sun lies in the visible region (0.38m < 0.7m) assuming that solar T = 5770KHint: we already know F(0.38m), so calculate F(0.7m) and interpolatelT (mmK x103)F0l(lT)(dimensionless)2.0673.2734.4815.6346.7388.85610.91412.94514.96316.97418.98120.986

UCL DEPARTMENT OF GEOGRAPHYElectromagnetic spectrumInteraction with the atmospheretransmission NOT even across the spectrumneed to choose bands carefully!56

UCL DEPARTMENT OF GEOGRAPHYDeparture from BB assumption?57

UCL DEPARTMENT OF GEOGRAPHYRecap58Objects can be approximated as blackbodiesRadiant energy T4EM spectrum from sun a continuum peaking at ~0.48m~39% energy between 0.38 and 0.7 in visible regionPlancks Law - shape of power spectrum for given T (Wm-2 m-1)Integrate over all to get total radiant power emitted by BB per unit areaStefan-Boltzmann Law M = T4 (Wm-2)Differentiate to get Wiens law Location of max = k/T where k = 2898mK

UCL DEPARTMENT OF GEOGRAPHYCaveats!Remote sensing has many problemsCan be expensiveTechnically difficultNOT directmeasure surrogate variablese.g. reflectance (%), brightness temperature (Wm-2 oK), backscatter (dB) RELATE to other, more direct properties.59

UCL DEPARTMENT OF GEOGRAPHYExample biophysical variables60

From Jensen, p. 9

UCL DEPARTMENT OF GEOGRAPHYExample biophysical variables61

From Jensen, p. 9Good discussion of spectral information extraction:http://dynamo.ecn.purdue.edu/~landgreb/Principles.pdf

UCL DEPARTMENT OF GEOGRAPHYREADJensen (2007) Chapters 1, 2 etc.

Disney (2015, forthcoming book chapter) Remote sensing of vegetation: potentials, limitations, developments and applications, ON WEB PAGEGrace et al. (2007) Can we measure photosynthesis from space? ON WEB PAGEESA (2006) The Changing Earth: Challenges for EO ON WEB PAGE

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UCL DEPARTMENT OF GEOGRAPHY62EXPLOREVery high res (cm to m) commercial satellite image galleries hours of fun!http://www.satimagingcorp.com/GeoEYE 1, 2, WorldView 1-3, Pleaides, QuickBird, IKONOS, SPOT etc.ESA and NASA image gallerieshttp://www.esa.int/Our_Activities/Observing_the_Earth/Image_archivehttp://earthobservatory.nasa.gov/ Landsat data archive free 28m data 1970s to presenthttp://glovis.usgs.gov/

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UCL DEPARTMENT OF GEOGRAPHY63EXPLORENASA data more generally (free, mostly) via REVERBhttp://reverb.echo.nasa.gov/reverb/#utf8=%E2%9C%93&spatial_map=satellite&spatial_type=rectangle PlanetLabs constellation of 10s-100s of cubesats 2013++https://www.planet.com/Skybox Imaging HD video from spacehttp://www.skyboximaging.com/https://www.youtube.com/watch?v=aW1-ZWencvA

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UCL DEPARTMENT OF GEOGRAPHY64Particle model of radiation65

From: http://abyss.uoregon.edu/~js/glossary/bohr_atom.html

UCL DEPARTMENT OF GEOGRAPHYParticle model of radiation: atomic shells66

http://www.tmeg.com/esp/e_orbit/orbit.htm

UCL DEPARTMENT OF GEOGRAPHYPlancks Law of blackbody radiation67Planck was able to explain energy spectrum of blackbodyBased on quantum theory rather than classical mechanicsdE()/d gives constant of Wiens LawE() over all results in Stefan-Boltzmann relationBlackbody energy function of , and T

http://www.tmeg.com/esp/e_orbit/orbit.htm

UCL DEPARTMENT OF GEOGRAPHYAside: Maxwells Equations681. Gauss law for electricity: the electric flux out of any closed surface is proportional to the total charge enclosed within the surface

2. Gauss law for magnetism: the net magnetic flux out of any closed surface is zero (i.e. magnetic monopoles do not exist)

3. Faradays Law of Induction: line integral of electric field around a closed loop is equal to negative of rate of change of magnetic flux through area enclosed by the loop.

4. Amperes Law: for a static electric field, the line integral of the magnetic field around a closed loop is proportional to the electric current flowing through the loop. Note: is divergence operator and x is curl operator; 0 is permittivity of free space; 0 is permeability of free spacehttp://en.wikipedia.org/wiki/Maxwell's_equations

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