Introduction to Finite Element Concepts
Introduction to Finite Element Concepts CEE 6900
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This 43 page Class Notes was uploaded by Timmothy Windler on Wednesday October 21, 2015. The Class Notes belongs to CEE 6900 at Tennessee Tech University taught by Faisal Hossain in Fall. Since its upload, it has received 15 views. For similar materials see /class/225707/cee-6900-tennessee-tech-university in Civil and Environmental Engineering (CEE) at Tennessee Tech University.
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LECTURE 2 What is Remote Sensing 1 What is Remote Sensing Lecture Outline Definition of Remote Sensing Electromagnetic Radiation Electromagnetic Spectrum Interactions with the Atmosphere Radiation Target Interactions Passive and Active Sensing Satellites and Sensors Interactions with the Atmosphere Particles and gases in the atmosphere can affect incoming radiation These effects are caused by the mechanisms of scattering and absorption Scattering causes EM radiation to be redirected from its original path Rayleigh scattering when particles are very small compared to the wavelength of radiation Mie Scattering when particles are just about the same size as the wavelength of radiation 39 Nonselective scattering when particles are much larger than the wavelength of radiation Absorption molecules in the atmosphere absorb energy 39 Ozone absorbs ultraviolet radiation from the sun 39 Carbon dioxide absorbs in the far infrared portion of the spectrum 39 Water vapor absorbs longwave infrared and shortwave microwave radiation Interactions with the Atmosphere The notion of Atmospheric Window Awath Transmlsslon quotm E uv VlSlELE NFRARED MICROWAVE Enevgy I 239 j i a 3 a Wavelength Those areas of the spectrum which are not severely in uenced by atmospheric absorption and thus are useful to remote sensors are called atmospheric windows The Visible portion of the spectrum to which our eyes are most sensitive corresponds to both an atmospheric window and the peak energy level of the sun Radiation Target Interactions Three forms of interaction take place where energy is incident upon the surface absorption transmission and re ection In remote sensing we are most interested in measuring the radiation re ected from targets ER xi x 1 00 E1 1 The re ection of the energy depends on the degree of surface roughness Spectral Re ectance 1 of the target relative to the wavelength of the energy incident on it When the roughness of a surface or height variations is small compared to the wavelength of radiation the surface acts as a mirror where the incident energy is directed away from the surface at angle equal to the angle of incidence specular re ection The other extreme case occurs when the surface is rough ie the height variations of the surface are much greater than the wavelength of the radiation In this case the radiation is re ected uniformly in all directions Thus type of re ection is called diffuse re ection Most of the earth s features lie between specular and diffuse re ection Radiation Target Interactions Examples r W e l 39S quot Qr Leaves A chemical compound in leaved called chlorophyll strongly absorbs radiation in the red and blue wavelengths but re ects green wavelengths Leaves appear greenest to us in the summer when cholorophyll content is at its maximum In autumn there is less chlorophyll in the leaves so there is less absorption and proportionately more re ection of the red wavelengths making leaves appear red or yellow If our eyes sensitive to nearinfrared trees would appear extremely bright to us at these wavelengths In fact measuring and monitoring the nearIR re ectance is one way that scientists can determine how healthy or unhealthy vegetation may be Radiation Target Interactions Examples 7 R m E Water Longer wavelength visible and near infrared radiation is absorbed more by water than shorter wavelengths Thus water tropically looks blue or bluegreen due to stronger re ectance at these shorter wavelengths and darker if viewed at red or near infrared wavelengths Chlorophyll in algae absorbs more of the blue wavelengths and re ects the green making the vegetation may be Radiation Target Interactions Spectral Re ectance Curve 2 5 Re ectance o 04 5 05 N 05 as Wavelength um Depending on the makeup of the target that is being observed and the wavelengths of radiation involved we can observe very different responses to the mechanisms of absorption transmission and re ection By measuring the energy that is re ected or emitted by targets on the Earth s surface over a variety of different wavelengths we can build up a spectral re ectance curve for that object Radiation Target Interactions Water and vegetation may re ect somewhat similarly in the visible wavelengths but are almost always separable in the infrared Spectral response can be quite variable even for the same target type and can also vary with time and location Knowing where to look spectrally and understanding the factors which in uence the spectral response of the features of interest are critical to correctly interpreting the interaction of electromagnetic radiation with the surface We almost always need to look at more than one wavelength frequency window to be able to detect differences and identify targets with a high degree of reliability LECTURE 11 Active Microwave Radar Active Microwave Lecture Outline Introduction Radar Hardware Radar Equation for a single scatterer Radar Equation for distributed meteorological targets Passive and Active RS Systems J Passive remote sensing systems record electromagnetic energy that is re ected eg blue green red and nearinfrared light or emitted eg thermal infrared energy from the surface of the Earth J Active remote sensors create their own electromagnetic energy that 1 is transmitted from the sensor toward the target and is largely unaffected by the atmosphere 2 interacts with the target producing a backscatter 0 energy and 3 is recorded by the remote sensor s receiver Active RS Systems The most widely used active remote sensing systems include J active microwave RADAR based on the transmission of long wavelength microwaves eg 1 cm7 1 m through the atmosphere and then recording the amount of energy backscattered from the target J LIDAR which is based on the transmission of relatively short wavelength laser light eg 090 mm and then recording the amount of light backscattered from the target and J SONAR which is based on the transmission of sound waves through a water column and then recording the amount of energy backscattered from the bottom or from objects within the water column Radar Basics Radar is an active remote sensing system operating at the micrawave wavelength Microwave Bands 10 GHz 1 GHz 02 pm 10 Iim 10 pm 1 mm 1 cm 10 cm 1 m I I I I Visible I Middle IR Thermal infrared UV Nearinfrared Radar is a ranging instrument RAdio Detection And Ranging Basic Principles QM The sensor transmits a microwave signal towards a target and detects the backseattered radiation The strength of the backscattered signal indicates the target property The time delay between the transmitted and re ected signals determines the distance or range to the target Advantages of Radar I Allrwealher I Daymghl magmg I Image can be produced from dxfferent type orpolanzed energy HIx HV W VH I Numerou Apphcauonxz r Detecuonanalym ofmeteorologxcal phenomena 7 Navx anon 7 Law Enforcement etcv Radar Hardware Radar Hardware Transmitter V It generates the high frequency signal which leaves the radar s antenna and goes out into space Modulator V It tells the transmitter when to transmit and for what duration Anterma V It directs the radars s signal into space V Most antennas used with radars are directional that is they focus the energy into a particular direction and not in other directions Waveguide V Connect the transmitterreceiver and the antenna Radar Hardware TransmitReceive Switch V The switch protects the receiver from the high power of the transmitter V Most radars transmit from lKW 7 lMW of power but receive powers as small as lO39lOW or less Receiver V Designed to detect and amplify the very weak signals received by the antenna V Radar does more listening than talking Over the period of an hour the radar spends 7 seconds emitting radiation and 59 minutes and 53 seconds listening for returned signals Radar Hardware Displays Plan Position Indicator PPI Radar Hardware Displays Range Height Indicator RHI Fundamental Properties of Emitted Beam Pulse Repetition Frequency PRF Represents how many pulses of radiation are transmitted per second 325 for typical weather radars magnum O distanl mgea mm pulse Transmission Time The duration of each pulse The pulse length the spacing between range gates I km on average Beam Illumination Fundamental Properties of Emitted Beam Beam Power Structure Gaussmn decay for small angles 1 the beam illumination 13xp 2 2 first Sidelobe function is approx Gaussian 72 62 7 2 18xp w 7 0 or second sidelobe beam width 0 B 62 10 j t r Sidelobe isolation 61010gl716m2 ya 6 Sidelobes are the main cause of ground clutter Relative 0neWa Antenna Gain dB 0 1 beam width 6 1 2 3 4 5 6 A ular Distance from Beam Axis deg The Rad by the Fundamental Properties of Emitted Beam Antenna Gain is defined as the ratio of the power received at a point where the maximum power exists P2 to the power that would be received at the same point from an isotropic antenna P1 unitless g u u G lOlog decibels dB 1 Typical antenna gains range from 20 dB to 45 dB Wat is the gain of an isotropic antenna Fundamental Properties of Emitted Beam The pulse length and the beam width determine the pulse volume The pulse volume can be huge at long ranges meaning that consecutive pulses will receive backscattered radiation from a large number of targets Fundamental Radar Equation 11 r the total radar power r 1 range Power reserved by angle target with cattenngcroxx ectron A W PagAe 47W2 r R a a My2 4702 for phencal antennax The effectwe antenna me ml 1 P 212A mu the nngle catterer radar retum power W 1 R W angle mam radar equauon 7 r Weather Radar V The radar samples a certain volume in space This sample volume is given by ELM 2 22 V 7 Where h is the pulse length 9 and j are the horizontal and vertical beam widths V Using a Gaussian shape of beam pattern the volume of a radar pulse volume is m26 h 16 1112 V We need to know the total backscattering crosssectional area of the radar sample volume A convenient way to do this is to determine the backscattering crosssectional area ofa unit volume and multiply this by the total sample vo ame at VZ Aw vol Weather Radar V Substituting this into the radar equation for a single scatterer gives P 2 2 P M 1024ln27r2r2 V What is the value of the backscattering crosssectional area V For most meteorological radars ie wavelengths of 3 cm and larger almost all raindrops can be considered small compared to the wavelength so the Rayleigh approximation applies retail 7 Au Where AG is the backscattering crosssectional area IKI2 is the complex index of refraction and D is the diameter of the sphere V The value of IKI2 depends upon the material the temperature and the wavelength of the radar For water IKI2 093 for ice IKI2 0197 Weather Radar V Substituting the expression for the backscattering crosssectional area gives R Fas ZWKlZZDf Pr 22 10241n2i r V This equation is perfectly fine for calculating the power received from a sample of raindrops providing we know the diameters ofall ofthe individual drops Obviously this is not going to happen most of the time V To get around this problem we define one final parameter called the radar re ectivity factor 2 2 D6 vol Again the summation is carried out over a unit volume not over the total sample volume of the radar Weather Radar V The Radar Equation Rnagz m Klzz P 39 10241n2zfr2 This equation is quite general it can be applied to any radar and target provided the particles meet the Rayleigh assumption V Simpli ed Radar Equation C1 is frequently called the radar constant onva Envimnmental Aggb39ca an a Remote Sznxing Lemquot Two 7 smug Sensors and arms sham gt Assrgn Readmg rnatena1 7 Chapter 2 oftextbook Mustread all before next e1ass gt HW2 Due nextweek ePrepare a eornprehensrve doeurnent on one of the followmg sate1hte rnrssrons 1 LANDSAT 2 TOPEXPOSEED ON 3 T12R05 4 TRMM 5 AQUA o CLOUDSAT 1n the report you rnust desenbe r rnrssron objectives n benefreranes who wruhave bene tbenefxted7 m types of wmw vn data proeessrng where to get the data7 vm one good appheatron of the rnrssron forwater or envrronrnental management there wru be lots ofpapers m the hterature gt Cover the fouowrng 1eeture m 2nd e1ass 3 hours gt Reeap wrth ppt pdf In order for a sensor to eoueet andreeord energy re eeted or emmedfrom atarget or sur ae rtrnustresrde on a stable platfnrm removed from the target or surface bemg observed Platforms for rernote sensors may be srtuated on the ground on an arreratt or balloon or some other platform wrthrn the Earth s atmosphere or on a spacecraft or sate1hte outsrde ofthe Earth s atmosphere n a eases th r n Senang 6556900 Envimnmental Aggb39ca anx a Remote Sewing Lecmnz Two 7 swung Serum and chin 3kmquot Sensors may be plaeed on a ladder scaffoldlng tall bulldlng cherryrplcker erahe ete used of data over vmually any ponlon ofthe Earth s surface at any tame 1h spaee remote sehsrhg ls somehrhes conducted from the space shuttle or more mm M Frm HM 39 ths ease the Earth For example the moon ls ahatural satelhte whereas maherhade t lltt n W factonn chooslng among the vanous platform ophorts vanety of platforms to vlew and lmage targets Although groundrbased and atreralt y Y be Sehahg onva Envimnmental Licazian a Remote Sznxin Lemquot Two 7 Smellitzx Sznxars and arm sham commonly usedtoday Satellites have several unique characteristics which make mcm particularly useful for remote sensing ofthe Emma surface m cm 1 cc 0001M m V r ofthe Emh so mcy seem stationary relative to mc Earth s surface This allows mc satellites to observe and couch information commuousiy over specific areas Wcamcc and communications satellites commonly have mcsc types of orbits Due to mcic high mud covcmng an cmicc hemisphere of mc Emh Trivia 39 39 the ground Prnve it using physics Ema credit Scnong 6556900 Envimnmenml AEEELWHIAHIS a Remote Sensing Lecnmz Two 7 swung Sznxars and chin 31mm 1L anchch m h the Earth s surfaee over a certam penod ofarrle These are nearrpnlar nrhits so named for L l a poles area othe world at a constant loeal me of olay calledlncal sun u39me At any glven latitude the posltlon of the sun m the sky as are satelllte passes overhead wlll be are same of olays Thls ls an lmponantfactor formomtonng changes between lmages or for rllumrrlauorl Cond lons Senang 6556900 Envimnmenml AEEELWHIAHIS a Remote Sensing Lecmnz Two 7 swung Sznxars and chin 31mm Most ofthe remote senslng satelllte platforms today are m nearrpolar orblts whlch means respeetavely Ifthe orblt ls also surrsyrrelrrorrous the ascendmg pass ls mostllkely on the recordmg re eeteol solar energy onlylmage the surface on a descendmg pass when solar ascendlng passes W W Yrseesr t r tr surface M w m P r Asthe Earth dldw lr H H r westward beeause the Earth ls rotatarrg from westto east beneath rt ms apparent a Ecru I an Senang onva Envimnmental Aggb39ra an a Remote Sznxing Lemquot Two 7 smug Sensors and arms sham Ifwe start wrth any randomly se1eeted pass m a satelhte s orbrt ah orbrt cycle wru be 0 w over surface duectly below the satelhte eaned the nadir porht for a seeohdtrrhe The exaet length ofume ofthe orbrta1 cycle wru vary wrth eaeh satelhte The rhterval ofume reqmred forthe satelhte to eorhplete rts orbrt cycle rs hot the same as the revisit period Usmg steerable sehsors ah satelliterbome rhstrurheht ear mew an area om nadu39 before and after the orbrtpasses over atarget thus makjng the revxsxt trrhe 1ess arhpt to mohrtor the spread of art or1 soul or the extent of oodmg 1h nearrpolar orbrts areas at hrgh 1atatudes wru be rrhaged more frequendythan the equatohal zohe due to the poles Tun r cnverzge Extra or edit Sehahg 6556900 Envimnmental Alabamaquot a Remote Sensing Two 7 Sm Lecmnz Hire Sensors and chin 31mm SPATIAL RESOLUTION PDEL SIZE AND SCALE th n WVw o a a n wn n The astronaut rnrght see your whole proyrnee or eountry In one glance but couldn t mdwxdual buxldmgs andears but you wouldbe yrewrng arnueh srnaner area than the astronaut There rs a srrnuar dAfference between sateurte rrnages and auphotos Sp atial Resnluu39nn andrefers to the srze of the smallest possrble feature that can be deteeted Spatral sensors Tater depends pnmanly on unerrInstantanenusFiem anizw IFOV The r seen B The srze ofthe area yrewedrs deterrnrnedby multrplyrng the IFOV by the dutance dt td Tm allowmg subrpxxel or resoluu on eeu deteeu on s we rnenuonedrn 1eeture 1 rnostrernote sensrng rrnages are eornposed of arnatnn of preture elements or pixels whreh are the srnanestunrts ofan Image Image purels are Senang 6556900 Envimnmental Aggb39ra an a Remote Sensing Lecmnz Two 7 swung Sznxars and Piggams 31mm resolutmh each prxel represents an area of 20m x 20m on the ground In thrs case the W var the sehsorthat eoueetedthe rrhagery remams the same metres to sever lometers Generally speakmg the finer the resolutmh the 1esstots1 ground area can be seen W to actual Kyou had amap wrth a scale ofl 100000 an object of 1m length on the map would 0 L a 100000erh M mapetoegrouhdrahoy are refenedto as srhsn scale s g 1 100000 andthose wrth largerrauos e g 1 5000 are calledlarge scale Sehshg 6556900 Envimnmental Alabamaquot a Remote Sewing Lecmnz Two 7 swung Serum and chin 3kmquot SPECTRAL RESOLUTION ea g at g leesmne t m Amuse 5 l 20 Basal a as as he tn 2 waveie gm 399 Carts 1 cl Rr d l u h water t M d t h n and near mfrared Other more speclflc classes such as di 39erentrncktypes may not be cornpanson at rnuch nerwavelength ranges to separate thern Thus we wouldrequlre a WWW r the wavelength range for apartrcular channel orband 04 um a 7m Black amp Wnne Fmquot EluevGreeaned n 4 29mm Fllm Blue Green n acts I an Black and whlte lrn records wavelengths extendmg overrnuch or all of the vlslble 39 as the resolutron as rtrs lndwldually sensrtwe to the re ected energy at the blue green andred Senang 6556900 Envimnmental Aggb39ca anx a Remote Sensing Lecnmz Two 7 swung Sznxars and chin 3kmquot Thu therrre eetanee in eaeh of these distinct wavelength ranges be visible nearernfrared and midrlnfrared portions of the eleetromagneue speetrum Their based on their speetral response in eaeh of the narrow bands Radinmetric Resnlutjnn While the arrangement ofplxels desenbes the spaual strueture ofan image the 1 eleetromagnetre energy determines the radinmetrie resnludnn The radiometrre m m r w m it is to deteeung small dlfferences in re eeted or emitted energy Imagery data are represented by posruve digital numbers whreh vary from 0 to one less numbers in binary format Eaeh brtreeords an exponent ofpower 2 e g lblt2 12 T axlmum number ofbnghmess levels available depends on the number ofblts used s there would be 28256 digital values available ranging from 0 to 255 However if only 4 bits were used then only 2416 values ranging from 0 to 15 wouldbe available Thus the of grey tones with black represenung a digital number of 0 and white represenung the mammum value for example 255m debit data By cnmparing alehit image with an Senang onva Envimnmental Aggb39ra an a Remote Sznxing Leann Two 7 Smellitzx Serum and P armx sham Srhitinge we ean see that there Is alarge dlfference In the level of detarl dseemrble dependlng on therr radlomemc resoluhons Temp oral Resolution W I n tinnls also rrnportantto Conslder In arernote senslng system We alludedto ths ldealn seehon 2 2 when we dseussedthe eoneept ofrevlslt penod whlch refers to th length oftrrne rt takes for a satelhte to eornplete one r rt eyel res In e entlre o b e The revIsI al e grind HOWEVER BECAUSE OE SOIer DEGREE RLAP IN THE IMAGING SWATHS OE ADJACENT ORBITS EOR MOST SATELLITES AND THE INCREASE IN THIS OVERLAP WITH INCREASING LATITUDE SOIer AREAS OE THE EARTH TEND TO RE RE IMAGED MORE FREQUENTLY Such as the polar regjnns Also some satelhte satellrte passes separated by penods from one to ve days Thus the aetual ternporal eapabrhhes the swath overlap andlatrtude Speetral eolleetrng and Companng multirtemp oral Imagery For example dunng the growlng rnonrtor those subtle Changes uslng rernote senslng ls dependent on when and how n able to rnonrtor the Changes that take plaee on the Earth s surface whether they are rrnportant when persrstent elonds offerllmlted elear vlews ofthe Earth s surface often In the txoplcs Sennng 6556900 Envimnmental Alabamaquot a Remote Sensing Two 7 Sm Lemquot Hires Sznxarsandl arms3haurs shortrllved phenomena oods 011 sheks ete needto be lrnaged t oneyeartothenent nearrslmllar features wheat maze scanning system whlch employ a sensor Wth a narrow eld of vlew l e IFOV that swee s x quot ndt th m t wdalnn mark scanning IncrAernseeraek scanan sean the Eath ln a senes of llnes The llnes are onented perpendeularto the dlrecuon ofrnotron ofthe rn VF rm l r m t the other usmg arntz ng mlrrnr A As the platform moves forward over sueeesswe seans bulld up atwoedlrnenslonal lrnage ofthe Earth39s surfaee The lneornrng deteeted lndependently The UV vrsrble nearrmfrared and therrnal radlatlon are dspersedrnto therr eonstltuent wavelengths Abank of lnternal detestan B eaeh speetral band and then as an electxlcal slgnal they are eonvertedto dlgltal data and eorded for subsequent eornputer proeesslng The mov C ofthe sensor andthe altltude ofthe platform deterrnrne the grnund wd e angles between 90 and 120 whlle satellltes beeause oftherr hlgher altltude need only e Senang 6556900 Envimnmental AEEELWHIAHIS a Remote Sensing Lecmnz Two 7 swung Sensors and chin 31mm sees speetral and radlometnc resoluuon othe sensor Alnngrtrzck scanan also use the forward lm H r m lens systerns cl whlch are pushed along m the rghttraek ddrechon l e along traek L rannm F hlwdl ldu r V Vlw IFOV t n r array ls requrredto rneasure eaeh speetral band or ehannel For eaeh sean hne the energy ree orded seanners The array of deteetors comblned wth the pushbroom rnotron allows eaeh deteetor to see and rneasure the energy from eaeh groundresoluuon eell for a longer nan r 4 Thu llhtrrmurl n r wd are more rellable andlast longer beeause they have no rnoylng parts on the otherhand neeessary and eornpheated Regardless of whether the seannlng systern usedls ether of these two types lthas seyeral Senang CEE 6900 Environmental Agglications of Remote Sensing Lecture Two Satellites Sensors and Platform 3honrs than photographic systems Multiband or multispectral photographic systems use separate lens systems to acquire each spectral band This may cause problems in ensuring that the different bands are comparable both spatially and radiometrically and with registration of the multiple images MSS systems acquire all spectral bands simultaneously through the same optical system to alleviate these problems Photographic systems record the energy detected by means of a photochemical process which is difficult to measure and to make consistent Because MSS data are recorded electronically it is easier to determine the speci c amount of energy measured and they can record over a greater range of values in a digital format Photographic systems require a continuous supply of film and processing on the ground after the photos have been taken The digital recording in MSS systems facilitates transmission of data to receiving stations on the ground and immediate processing of data in a computer environment SO WHAT TYPE OF SCANNING DO YOU USE WHEN YOU BRUSH YOUR ROOM WITH A BROOM ALONG TRACK OR ACROSS TRACK Acknowledgements These lecture notes have been modified from the Canada Center for Remote 14 Sensing 6556900 Envimnmental Alabamaquot a Remote Sensing Lecmnz Two 7 swam Sznxars and chin 31mm THERMAL IMAGING Detecmr Electronics Lens M eer Many multxspectxal MSS systems sense radAanon m the thermal rnfrared as well as the r r m t n w o energy emmedfrom the Earth s surface m the thermal rnfrared 3 pm to 15 um rs radAanon therr own thermal emrssrons Therma1 sensors essenuany measure the surface temperature and thermal properues of targets n a speetrum Thermal sensors emp1oy one ormore rnterna1 temperature references for temperature The data are generally reeorded on lm andormagneue tape and the 1 F r w w w of relauye radAant temperatures athermngram rs depretedrn grey 1eye1s wrth warmer temperatures shown m hghttones and eoo1ertemperatures m dark tones Imagery whreh Senang CEE 6900 Environmental Agglications of Remote Sensing Lecture Two Satellites Sensors and Platform 3honrs accurate calibration and measurement of the temperature references and detailed knowledge of the thermal properties of the target geometric distortions and radiometric effects Because of the relatively long wavelength of thermal radiation compared to visible radiation atmospheric scattering is minimal However absorption by atmospheric gases normally restricts thermal sensing to two specific regions 3 to 5 pm and 8 to 14 um Because energy decreases as the wavelength increases thermal sensors generally have large IFOVs to ensure that enough energy reaches the detector in order to make a reliable measurement Therefore the spatial resolution of thermal sensors is usually fairly coarse relative to the spatial resolution possible in the visible and re ected infrared Thermal imagery can be acquired during the day or night because the radiation is emitted not re ected and is used for a variety of applications such as military reconnaissance disaster management forest fire mapping and heat loss monitoring Weather Satellites and Sensors Weather monitoring and forecasting was one of the first civilian as opposed to military applications of satellite remote sensing dating back to the first true weather satellite TIROSl Television and Infrared Observation Satellite I launched in 1960 by the United States Several other weather satellites were launched over the next five years in nearpolar orbits providing repetitive coverage of global weather patterns In 1966 NASA the US National Aeronautics and Space Administration launched the geostationary Applications Technology Satellite ATSl which provided hemispheric images of the Earth39s surface and cloud cover every half hour For the first time the development and movement of weather systems could be routinely monitored Today several countries operate weather or meteorological satellites to monitor weather conditions around the globe Generally speaking these satellites use sensors which have fairly coarse spatial resolution when compared to systems for observing land and provide large areal coverage Their temporal resolutions are generally quite high providing frequent observations of the Ea1th s surface atmospheric moisture and cloud cover which allows for near continuous monitoring of global weather conditions and hence forecasting Here we review a few of the representative quotquot used for 39 39 39 applications GOES Acknowledgements These lecture notes have been modified from the Canada Center for Remote 16 Sensmg 6556900 Envimnmental Aggb39ra ans a Remote Sensing Lecmnz Two 7 swam Sznxars and chin 3kmquot he GOES Geostauonarv Operauona1 39r u n c t n t A M t the Unrted States Natrona1 Weather Servree wrth frequent smallrscale 1magmg othe The GOE by meteoro1ogrsts for weather monrtonng and foreeasung for over 20 years These Two GOES sate1htes p1aeeo1m genstau39nnary nrhits 36000 km above the equator eaeh mew W N rth m1 uth t1 Oeean 135 w from 20mm 16st 1ongrtuo1e Thrs GOES 1mage eovers aporuon ofthe southeastern Wm d V V develop Thrs 1mage shows Humeane Eran approachmg the southeastern Unrted States andthe Eahamas m September of1996 re eeted radAauon from whreh atmosphene temperature Wmds mor ture and e1ouo1 eover ean be denved The rst generatron ofsate1htes eonsrsted of GOESrl 1auneheo1 1975 through GOESJ 1auneheo1 1992 Due to therr desrgn these sate1htes were eent The seeond generauon ofsate1htes began wrth GOESE 1auneheo1 1994 and has observauon othe Earth allowmg more frequentxmagmg as often as every 15 mrnutes wd quahtv for forecastmg meteoro1ogrea1 condmons hemrsphere or smallrscale 1magmg ofselected areas The 1atter a11ows meteoro1ogrsts to Th rn rut r p e 17 Senang CEE 6900 Environmental Agglications of Remote Sensing Lecture Two Satellites Sensors and Platform 3honrs imager data are 10bit radiometric resolution and can be transmitted directly to local user terminals on the Earth39s surface The accompanying table describes the individual bands their spatial resolution and their meteorological applications GOES Bands Wavelength Spatial iBand Range um Resolution Apphcamn 052 072 cloud pollution and haze detection severe storml l 1km 2v1s1ble 1dent1f1catron identi cation of fog at night discriminating 2 378 403 4 km water clouds and snow or ice clouds during 2shortwave IR daytime detecting res and volcanoes night i time determination of sea surface temperatures l 647 702 estimating regions of midlevel moisture content 3 upper level water 4 km and advection tracking midlevel atmospheric l vapour motion l4 102 112 4 km identifying clouddrift winds severe storms and l longwave IR heavy rainfall l identification of lowlevel moisture 5 4 km determination of sea surface temperature ssensrtrve to water l detectron of a1rbome dust and volcan1c ash vapour The 19 channel sounder measures emitted radiation in 18 thermal infrared bands and re ected radiation in one visible band These data have a spatial resolution of 8 km and 13bit radiometric resolution Sounder data are used for surface and cloudtop temperatures multilevel moisture profiling in the atmosphere and ozone distribution analysis NOAA AVHRR NOAA is also responsible for another series of satellites which are useful for meteorological as well as other applications These satellites in sun synchronous near polar orbits 830870 km above the Earth are part of the Advanced TIROS series originally dating back to 1960 and provide complementary information to the geostationary meteorological satellites such as GOES Two satellites each providing global coverage work together to ensure that data for any region of the Earth is no more than six hours old One satellite crosses the equator in the early morning from northto south while the other crosses in the aftemoon The primary sensor on board the NOAA satellites used for both meteorology and small scale Earth observation and reconnaissance is the Advanced Very High Resolution Radiometer AVHRR The AVHRR sensor detects radiation in the visible near and mid infrared and thermal infrared portions of the electromagnetic spectrum over a swath Acknowledgements These lecture notes have been modified from the Canada Center for Remote 18 Sensing CEE 6900 Environmental Agglications of Remote Sensing Lecture Two Satellites Sensors and Platform 3honrs width of 3000 km The accompanying table outlines the AVHRR bands their wavelengths and spatial resolution at swath nadir and general applications of each NOAA AVHRR Bands 1 Wavelength Range Spatial Band um Resolution Apphcatlon ll 9058 068 red 11 km cloud snow and ice monitoring 392 10725llnearIR 11km 3 355 393 mid IR 11km l 103 113 thermal 4 IR 11 km l 115 125 thermal 5 IR 11 km water vegetation and agriculture surveys sea surface temperature volcanoes and forest re activity sea surface temperature soil moisture sea surface temperature soil moisture AVHRR data can be acquired and formatted in four operational modes differing in resolution and method of transmission Data can be transmitted directly to the ground and viewed as data are collected or recorded on board the satellite for later transmission and processing The accompanying table describes the various data formats and their characteristics AVHRR Data Formats Format Spamil Transmission and Processing Resolutlon lAPT Automatic Picture lTransmission lHRPT High Resolution Picture l Transmission 4km 11km GAC Global Area Coverage 4 km LAC Local Area Coverage 11 km Acknowledgements These lecture notes have been modified from the Canada Center for Remote Sensmg lowresolution direct transmission and display fullresolution direct transmission and display lowresolution coverage from recorded data selected fullresolution local area data from recorded data 6556900 Envimnmenml Aggb39ca anx a Remote Seming Ledaquot Two 7 swung Serum and chin 31mm u KWquot u though AVHRR data arewrdely used r wellrsmted L atra1 resoluuor than other nd an and morutormg ofland features AVHRR has much coarser sp typrea1 temperature and uatura1 vegetauor and crop condmons Masaics covenng large areas canbe r tarrm VHRR w Other Weather Satellites Senang CEE 6900 Environmental Agglications of Remote Sensing Lecture Two Satellites Sensors and Platform 3honrs The United States operates the DMSP Defense Meteorological Satellite Program series of satellites which are also used for weather monitoring These are nearpolar orbiting satellites whose Operational Linescan System OLS sensor provides twice daily coverage with a swath width of 3000 km at a spatial resolution of 27 km It has two fairly broad wavelength bands a visible and near infrared band 04 to 11 pm and a thermal infrared band 100 to 134 pm An interesting feature of the sensor is its ability to acquire visible band night time imagery under very low illumination conditions With this sensor it is possible to collect striking images of the Earth showing typically the night time lights of large urban centres There are several other meteorological satellites in orbit launched and operated by other countries or groups of countries These include Japan with the GMS satellite series and the consortium of European communities with the Meteosat satellites Both are geostationary satellites situated above the equator over Japan and Europe respectively Both provide halfhourly imaging of the Earth similar to GOES GMS has two bands 05 to 075 pm 125 km resolution and 105 to 125 pm 5 km resolution Meteosat has three bands visible band 04 to 11 pm 25 km resolution midIR 57 to 71 pm 5 km resolution and thermal IR 105 to 125 pm 5 km resolution Acknowledgements These lecture notes have been modified from the Canada Center for Remote 21 Sensing onva Envimnmental Allb39ta anx a Remote Sznxing Lecmnz Two 7 Same Serum and Pl l annx shame LAND OBSERVATION SENSORS Very rmportantforthrs eourse and for hydro1ogrsts Landsat 1though many ofthe weather sate1hte systems sueh surface they are not opumrzed for detat1ed mapprng of the 1and surface Drwen by the t w tn th 1960 s as we11 as from 1mages taken dunng manned spaeeeratt mrssrons the rst sate1hte r e rth urr 1 nd 397 m 1972 Imtrany refenedto as ERTSrl Earth Resources Teehno1ogy Sate1hteLandeat 1 Ea h tn th tum tht ht m seyera1 Landsat sate1htes Ongmally managed by NASA responsrbrhty for the Landsat program was transferr dto NOAA m 1983 In 1985 the program beeame commercxahzedprov1dmg datato ewrhan and appheauons users w hxdw L L speetra1 htstoneal reeords andreseareh A11 Landsat satelhtes are placedm nearrpolar sunr synehronous orbtts The ftrstthree satelhtes Landsats 173 are at almudes around 900 km and 16 d 11 mormng to opumrze r11umrnauon condmons number een on board the Landsat senes of sate1htes mcludmg the e a systems the MuluSpeetral Scanner MSS A of sensors have b Return Beam Vidicnn REV amer systems and the Thematic Mapper TM The most popu1ar rnstrumentrn the ear1y days of Landsatwas the Mu1trSpeetra1 Seanner MSS and1ater the Themaue Mapper TM Eaeh ofthese sensors eo11eeted data yer a swath wrdth of 185 km wrth afull seene betng de ned as 185 km x 185 km Senang
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