GeomaticsisarelativelynewscientifictermcreatedbyPollockandWrightin1969,withtheintentionofcombiningthetermsgeodesyandgeoinformatics.ItincludesthetoolsandtechniquesusedinSurveyingandMapping,RemoteSensing(RS),Cartography,GeographicInformationSystems(GIS),GlobalNavigationSatelliteSystems(GNSS,i.e.,GPS,Glonass,Galileo,Compass),Photogrammetry,Geography,Geosciences,ComputerSciences,InformationScienceandvariousspatialobservationtechnologies,landdevelopmentandenvironmentalsciences,etc.測繪學(xué)是一種相對較新的科學(xué)術(shù)語由波洛克和賴特在1969年提出，目的是將大地測量學(xué)與地理信息學(xué)結(jié)合起來。它包括的工具和技術(shù)應(yīng)用于測繪、遙感(RS)、地圖學(xué)、地理信息系統(tǒng)(GIS)、全球?qū)Ш叫l(wèi)星系統(tǒng)(GNSS,即。、GPS、Glonass、伽利略、北斗),攝影測量、地理學(xué)、地球科學(xué)、計算機科學(xué)、信息科學(xué)和各種空間觀測技術(shù)、土地開發(fā)、環(huán)境科學(xué)等。Surveyingmaybedefinedasthetechnologyandscienceofthestudyofearth’sshapeandsize,aswellasmakingmeasurementsoftherelativepositionsofnaturalandman-madefeatureson,aboveorbelowtheearth’ssurface,andrepresentingtheseinformationinanalogformsascontouredmapsorsections,paperplanorchart,orasfiguresinreporttables,orindigitalformasathreedimensionalmathematicalmodelstoredinthecomputer.測量的技術(shù)和科學(xué)可以定義為研究地球的形狀和大小,以及測量位于地球外表上或者低于或者高于地球外表的自然的或人造的物體的相對位置,并將這些信息以模擬形式的波狀外形的地圖、剖面圖、論文方案、圖表、數(shù)據(jù)報告表中呈現(xiàn)或以數(shù)字形式存儲在計算機三維數(shù)學(xué)模型中。Surveysarethetechnologiesofmeasuringhorizontalandverticaldistancesbetweenobjects,measuringanglesbetweenlinesorthedirectionoflines,anddeterminingtheelevationsofthepoints.Aftertheactualmeasurementsofsurveys,mathematicalcalculationsaremadetodeterminethedistances,angles,directions,locations,elevations,areas,andvolumesfromsurveyingdata.Thenmuchsurveyinginformationisportrayedgraphicallyinformsoftheconstructionmaps,profiles,cross-sectionsanddiagrams.測繪學(xué)是測量物體之間的水平和垂直距離,測量直線之間的角度或直線的方向,測量點位的高度的技術(shù)。在實際測量后,需要根據(jù)測量數(shù)據(jù)進(jìn)行數(shù)學(xué)計算來確定距離,角度,方向,位置,海拔,地區(qū)和體積。然后測量信息就以地圖、剖面圖、橫斷面圖和圖表等圖形形式描繪出來。Theequipmentsavailableandmethodsapplicableformeasurementsandcalculationshavechangedtremendouslyinthepastdecade.Traditionalequipmentsformeasurements:Optical(electronic)Theodolite,Tapes,ElectronicDistanceMeasurement(EDM),levels,etc.Modernequipments:Aerialphotogrammetry,satelliteobservation,RemoteSensing(RS),inertialsurveying,andlaserrangingtechniques,etc.Atthesametime,therelativelyeasyaccesstocomputersofallsizefacilitatestherigorousprocessingandstorageoflargevolumesofdata.可用的設(shè)備和適用于測量和計算的方法在過去十年發(fā)生了巨大變化。傳統(tǒng)的測量設(shè)備:光學(xué)〔電子〕經(jīng)緯儀、磁帶、電子測距(EDM)、水準(zhǔn)尺等?，F(xiàn)代設(shè)備:航空攝影測量、衛(wèi)星觀測、遙感(RS)、慣性測量,激光測距技術(shù),等等。同時,電腦的相對廣泛應(yīng)用促進(jìn)了嚴(yán)格處理和存儲大量數(shù)據(jù)的過程。Withthedevelopmentofthesemoderndataacquisitionandprocessingsystems,thedutiesofthesurveyorshaveexpandedbeyondthetraditionaltasksofthefieldworkoftakingmeasurementsandtheofficeworkofcomputinganddrawing.Surveyingisrequirednotonlyforconventionalconstructionengineeringprojects,mapping,andpropertysurveys,butisalsousedincreasinglybyotherphysicalsciences,suchasgeology,geophysics,biology,agriculture,forestry,hydrology,oceanographyandgeography,etc.隨著現(xiàn)代數(shù)據(jù)采集和處理系統(tǒng)的開展,測量員的職責(zé)已經(jīng)大大超出了傳統(tǒng)的野外測量工作和內(nèi)業(yè)計算和繪圖工作。測量不僅適用于傳統(tǒng)的建筑工程工程、地圖學(xué)和土地權(quán)屬調(diào)查,也越來越多的適用于其他物理科學(xué),如地質(zhì)、地球物理、生態(tài)學(xué)、農(nóng)學(xué)、林業(yè)學(xué)、水文、海洋、地理等。TheessentialworkofsurveyingistodetermineaccuratelythepositionofthefeaturesonthesurfaceoftheEarth(horizontalsurveying),andtheelevationsofthefeatures(verticalsurveying),oracombinationofboth.Althoughdifferentsurveysarefordifferentpurposes,thebasicoperationsinclude:measurements(fieldwork),computationsandmapping(officework).Fromanotherpoint,theworkofsurveyingiseithertodeterminethelocations(three-dimensionalcoordinates)ofgroundfeaturesanddrawingallkindsofmaps,ortomarkoutthedesignedbuildingsorstructuresinmapsattheirproposedpositions.測量的根本工作是確定地球上物體的準(zhǔn)確位置(水平測量)和高度(垂直測量),或兩者的結(jié)合。雖然不同的調(diào)查是為了不同的目的,根本操作包括:測量(野外),計算和繪圖(內(nèi)業(yè))。從另一個角度,測量的工作是確定地球表現(xiàn)上物體的位置(三維坐標(biāo))和繪制各種地圖,或在地圖上的建筑物、構(gòu)筑物中標(biāo)定他們的位置。Surveyingoperationsinclude:(1)designofsurveyingproceduresandselectionofequipments;(2)acquisitionandstorageofdatainthefields;(3)reductionoranalysisofdataintheofficeorinthefiled;(4)preparationofmapsorotherdisplaysinthegraphicalornumericalformsneededforthepurposeofsurvey;(5)layoutofmonumentsandboundariesinthefields,aswellasprovidingcontrolsurveyingforconstruction.測量操作包括:(1)測量過程的設(shè)計和測量儀器的選擇;(2)野外數(shù)據(jù)的采集和存儲;(3)在辦公室或野外分析和處理數(shù)據(jù);(4)準(zhǔn)備測量所需的地圖或其他以圖形或數(shù)字形式的呈現(xiàn)的圖形;在野外埋設(shè)標(biāo)石和邊界,進(jìn)行施工控制測量。Performanceofthesetasksrequiresafamiliaritywiththeusesofsurveyingequipmentsandtechniques,knowledgeoffundamentalsofthesurveyingprocess,andknowledgeofvariousmeansbywhichdatacanbepreparedforpresentation.Definitionsofcontrolsurveyinganddetailsurveying:(1)Controlsurveyingisreferredtothemeasurementsofcontrolpoints,whicharewellspacedintheformofnetworkandplaycontrollingrolesinsurveyarea.(2)Detailsurveyingisreferredtotheworkofmeasuringtheterrainfeaturesaroundeachcontrolpoint.這些任務(wù)的完成需要熟練使用測量設(shè)備和技術(shù),測量過程的根底知識和在地圖上展繪數(shù)據(jù)的各種知識。控制測量和碎部測量的定義:(1)控制測量的測量控制點,以網(wǎng)絡(luò)的形式分布在測區(qū)并在測區(qū)起控制作用。(2)碎部測量是測量每個控制點周圍的地形特征。Theworkofsurveyingshouldfollowsomebasicproceduresorrules:(1)Controlsurveyingshouldbefirstlycarriedout,andthendetailsurveying.(2)Theworkofsurveyingshouldbeconducedfromthewholetotheparts.(3)High-precisionsurveyingcontrolsthelow-precisionsurveying.(4)Eachstepofsurveyingworkhasacheck.Thesebasicproceduresorrulescanhelptodividesurveyingareaintodifferentmapunits,reducetheerroraccumulation,ensuretheprecisionofmapping,andspeedupthemappingprocess.測量工作應(yīng)該遵循根本的程序和規(guī)那么:(1)控制測量應(yīng)首先進(jìn)行,然后進(jìn)行碎部測量。(2)測量的工作應(yīng)該是從整體到局部。(3)高精度等級測量控制低精度等級測量。(4)步步要檢核。這些根本的程序或規(guī)那么可以把測量區(qū)域劃分為不同的地圖單元,減少誤差積累,保證了地圖的精度,加快制圖過程。Surveyshavemanydifferentbranches,suchasgeodeticsurveying,planesurveying,engineeringsurveying,topographicsurveying,cadastralsurveying,minesurveying,etc.1.GeodeticsurveyingGeodeticsurveyingisreferredtothemeasurementandrepresentationoftheEarth’sshapeandsize,gravityfieldandgeodynamicphenomena(suchaspolarmotion,Earthtidesandcrustalmotion),andestablishmentofcontrolnetworksoflargeareasforothersurveys.調(diào)查有很多不同的分支,如大地測量、平面測量,工程測量,地形測量、地籍測量、礦山測量學(xué)等。1、大地測量學(xué)大地測量是測量和表征地球的形狀和大小,重力場和地球動力學(xué)的現(xiàn)象(如極移、地球潮汐和地殼運動),建立用于其他大面積測量的控制網(wǎng)絡(luò)的學(xué)科。Ingeodeticsurveying,largeareasoftheEarth’ssurfaceareinvolvedandthetrueshapeoftheEarthmustbetakenintoaccount,andthestationsarenormallylongdistancesapart,andmorepreciseinstrumentsandsurveyingmethodsarerequiredforthistypeofsurveying.Ingeodeticsurveying,theshapeoftheEarthisthoughtofasaspheroid,althoughitisnotreallyaspheroidinatechnicalsense.在大地測量學(xué)中，由于地球外表的大局部地區(qū)都有涉及，所以地球的真實形狀必須考慮進(jìn)去,由于站點之間的分隔距離較遠(yuǎn),所以需要更精密的儀器和測量方法。在大地測量學(xué)中，地球的形狀被認(rèn)為是一個球體,雖然在理論意義上并不是一個球體。Therefore,distancesmeasuredonornearthesurfaceoftheEartharenotalongstraightlinesorplanes,butonacurvedsurface.Widelyspacedandpermanentmonumentsareusedasthebasisforcomputinglengthsanddistancesbetweenrelativepositions.allowancesaremadefortheearth’sminorandmajordiametersfromwhichareferencespheroidisdeveloped.Thesebasicpointswithpermanentmonumentsarecalledgeodeticcontrolpoints,whichsupporttheproductionofconsistentandcompatiblereferencecoordinatesforothersurveyingandmappingprojects.因此,在地球外表或者地球附近所測的距離并不是沿直線或平面的,而是在一個曲面上。廣泛放置的永久標(biāo)石可以作為計算長度和相對點位之間距離的根底。參考橢球面是根據(jù)地球的大小半徑的容許差來建立的。這些帶有永久標(biāo)石的根本點被稱為大地控制點,為其他的測量工作提供固定坐標(biāo)和相對坐標(biāo)。PlanesurveyingThetypeofsurveyinginwhichthemeansurfaceoftheearthisconsideredaplane,orinwhichthecurvatureoftheearthcanbedisregardedwithoutsignificanterror,generallyiscalledplanesurvey.Thetermisusedtodesignatesurveyworkinwhichthedistancesorareasinvolvedareoflimitedextent.平面測量在這種測量中地球平均外表被認(rèn)為是一個平面,或在沒有較大誤差的情況下地球曲率可以被忽略,這種測量通常被稱為平面測量。這種測量都用于指定的距離和面積在有限范圍內(nèi)的測量工作。Withregardtohorizontaldistancesanddirections,alevellineisconsideredmathematicallystraight,thedirectionoftheplumblineisconsideredtobeplaneangles.Inplanesurveying,formulasofplanetrigonometry,algebra,andanalyticalgeometryareusedtomakecomputations.Forsmallareas,preciseresultsmaybeobtainedwithplanesurveyingmethods,buttheaccuracyandprecisionofsuchresultswilldecreaseastheareasurveyedincreasesinsize.對與水平距離和方向,水平線在數(shù)學(xué)上被認(rèn)為是直的,鉛垂線的方向被認(rèn)為是平面角。在平面測量中，平面三角公式、代數(shù)、解析幾何是用來計算的。對小區(qū)域,平面測量方法可以獲得精確的結(jié)果,但結(jié)果的準(zhǔn)確度和精度將隨著測區(qū)的面積增大而降低。Thereareclosecooperationbetweengeodeticsurveyandplanesurvey.Thegeodeticsurveyadoptstheparametersdeterminedbymeasurementsoftheearth,anditsownresultsareavailabletothosewhomeasuretheearth.Theplanesurveysaregenerallyconnectedtothecontrolpointsofthegeodeticsurveys.大地測量和平面測量之間有密切的聯(lián)系。大地測量采用參數(shù)取決于所測量的地球平面,并且測量結(jié)果可被其他測量地球的人使用。平面測量通常與大地測量的控制點有關(guān)。3.TopographicsurveyingTopographicsurveysaremadetodeterminetheconfiguration(relief)ofthesurfaceoftheearth,locatethenaturalandartificialfeaturesthereon,andproducemaps,plansorsectionstosuitablescales.Manynaturalandartificialfeaturessuchasrelief,hydrography,vegetation,road,trails,buildings,canalsandboundarylineshavetoberepresentedbyconventionalsymbolsinatopographicmap.3.地形測量地形測量是用來確定地球外表形狀,確定自然和人工物體的位置,并生成地圖,選定平面圖和區(qū)域圖的適宜的比例尺。許多天然和人工物體,比方地貌、水文、植被、道路、小徑、建筑物、運河和邊界線必須由傳統(tǒng)的地形圖符號在地形圖中表示。Topographicmapshaveheightinformationeitherasspotheightsorascontours,andtheirscalesaredifferentranges.Topographicmapshaveamultitudeofuses,suchasnavigation,recreation,geographicalandgeologicalstudy,military,exploration,etc.地形圖上有點位高度表示的高程信息和以等高線表示的高程信息,他們的比例尺范圍不同。地形圖有多種用途,如導(dǎo)航、娛樂、地理和地質(zhì)研究、軍事、勘探等。4.EngineeringsurveyingEngineeringsurveysarereferredtoallthesurveysrequiredindesign,constructionandmanagementstagesofengineeringconstructions.Forexample,inthestageofsurveyanddesign,large-scaletopographicalmapsorplansarerequiredasabasisfordesign,thentheproposedpositionofanynewitemoftheconstructionmustbemarkedoutonthegroundbothinplaneandheight,theseoperationsgenerallytermedsetting工程測量工程測量是指建筑設(shè)計、工程建設(shè)和工程建設(shè)的管理階段的所有測量工作。例如,在勘察設(shè)計階段,大比例尺的地形圖或設(shè)計作為設(shè)計的根底,并且提出任何新的建設(shè)工程的點位必須在平面上放樣出平面位置和高度,這些操作通常稱為放樣。settingout,andfinally,as-builtsurveysanddeformationmonitoringareoftenrequired.Thedesignandconstructionofnewroutes,e.g.roads,andrailways,thecalculationsoftheareasandvolumesoflandarealsotheaspectsofengineeringsurveys.放樣,最后竣工調(diào)查和變形監(jiān)測通常是必需的。新路線的設(shè)計和施工,如公路,鐵路,計算區(qū)域大小和土方量也屬于工程測量。5.CadastralsurveyingCadastralsurveysarereferredtotheworkofmakingmeasurementsandplottingthemeasurementstoproduceplansofpropertyboundariesforlegalpurposes.Inmanycountriestheregistrationsofownershipoflandsarebasedonsuchplans.地籍測量地籍測量是指進(jìn)行測量和繪制符合法律用途的合法邊界。在許多國家登記的土地的所有權(quán)是基于這樣的平面圖。6.MineSurveyingMinesurveyingisconcernedwithmeasurementsofsurfaceandundergroundmines,obtainingdataindigitalformandmakinggraphicalrepresentationforprospectingmineraldeposits,constructingminesandexploitingminerals.Afewcenturiesago,minesurveyingisextensivelydevelopedforthedeterminationoftheboundariesoftheminingclaims.Theearlyperiodofminesurveyingmaybeconsideredastheartofrunningundergroundtraverses.礦山測量學(xué)礦山測量學(xué)是測量外表和地下礦山、以數(shù)字形式獲取數(shù)據(jù),使圖形標(biāo)繪勘探礦藏,礦山建設(shè)和開采礦產(chǎn)。幾個世紀(jì)前,礦山測量學(xué)廣泛開展是為了采礦勘界的目的。礦山測量學(xué)的早期可能被視為布設(shè)地下導(dǎo)線。However,asitdeveloped,minesurveyingincluded,apartfromtechniquesofminesurveying,theminesurveyinginstrumentation,thegeometryofmineralresources,studyoftectonics,etc.Alltheseaspectsofminesurveyingaremadefortheprecisionofgeologicalexploration,aswellasthesafetyandefficiencyinworkingamine.Astheprogresshasbeenmadeinthemethodsofminesurveying,theminesurveyorsareusingthegyro-theodolite,high-precisiontheodolitesandopticalrangefinderstosolveoftheproblemsoforientationandconstructionofreferencenetworks.然而,隨著它的開展,礦山測量學(xué),除了礦山測量技術(shù)、礦山測量儀器,礦產(chǎn)資源的幾何構(gòu)造和技術(shù)研究等。礦山測量的所有這些方面構(gòu)成地質(zhì)勘探精度,以及礦井工作的平安性和效率。礦山測量學(xué)方法的進(jìn)步,礦山測量員使用陀螺經(jīng)緯儀、高精度經(jīng)緯儀和光學(xué)測距儀來解決定向和參照網(wǎng)絡(luò)的建設(shè)等問題。Self-adjustinglevelsandlasershaverecentlybecomeverypopulartogivelinesandgradesandcheckonthedirectionsofmines,andprovidecontrolforsuchoperationsasmineshaftequipment,layingrailwaytracks,installingconveyors,puttingthroughpipelinesandothers.Moreover,newtechniquesandinstrumentsaremadeforplottingminegraphicsandpreparingmineplansandlongitudinalandtransversesections.自動安平水準(zhǔn)儀和激光水準(zhǔn)儀最近變得非常流行在施工方樣和坡度以及檢核礦井方向等方面,并為礦井設(shè)備操作提供控制,鋪設(shè)鐵軌,安裝輸送機,放樣管道和其他事物。此外,新技術(shù)和儀器是用來鋪設(shè)井筒和繪制礦井平面圖和縱和橫向斷面圖的。Theearliestsurveyswereforthepurposeofestablishingtheboundariesofland,andsuchsurveysarestillimportantworkofmanysurveyors.Everyconstructionprojectofanymagnitudeisbasedtosomedegreeuponmeasurementstakenduringtheprogressofasurveyandisconstructedaboutlinesandpointsestablishedbythesurveyors.Asidefromlandsurveys,practicallyallsurveysofprivateandpublicnaturesareofassistanceintheconception,design,andexecutionofengineeringworks.最早的調(diào)查是為了建立土地的邊界,這樣的測量工作仍是測量員的重要工作。任何規(guī)模的建設(shè)工程都是在某種程度上基于測量以及測量員所放樣的點線。除了土地調(diào)查,幾乎所有的私有和公共性質(zhì)調(diào)查是概念、設(shè)計、工程和執(zhí)行工作的輔助設(shè)備。1.4DevelopmentsofSurveying1.SurveyingtechniquesHistorically,distancesweremeasuredbydifferentmeans,forinstancetapesmadeofsteelorinvarwerepulledtauttoreducesaggingandslacktomeasurehorizontaldistances.Additionally,attemptingtomeasureupaslope,thesurveyorsmighthavetouseincrementslessthanthetotallengthofthetape.Horizontalanglesweremeasuredusingacompass,whichwouldprovideamagneticbearing.Thistypeofinstrumentwaslaterimproved,withmorecarefullyscribeddiscsprovidingbetterangularresolution,aswellasthroughmountingtelescopeswithreticlesformore-precisesightingatopthedisc.從歷史上看,距離測量的方式有很多,例如使用拉緊的鋼尺或銦瓦尺減少下垂和松弛來測量水平距離。此外,為了測量斜坡,測量員可能使用增量法而不是總長度的鋼尺。使用帶有磁軸承的羅盤測量水平角度。這種類型的儀器后來有所改善,更仔細(xì)地刻劃度盤從而提供更好的角分辨率,以及通過望遠(yuǎn)鏡的十字刻劃絲來更精確的瞄準(zhǔn)度盤的頂部。High-accuracytransitsortheodoliteswereusedforthiswork,andanglesbetweenobjectsweremeasuredrepeatedlyforincreasedaccuracy.Historically,thesimplestmethodformeasuringheightswasusingairpressureasanindicationofheightwithanaltimeter(basicallyabarometer).Butsurveyingrequiresgreaterprecision.Avarietyofmeans,suchaspreciseleveling(alsoknownasdifferentialleveling),havebeendevelopedtodothis.Withpreciseleveling,aseriesofmeasurementsbetweentwopointsaretakenusingalevelinstrumentandalevelingrod.高精度經(jīng)緯儀被用于這項工作,通過增加物體之間角度測量次數(shù)來增加準(zhǔn)確性。測量高度的歷史上,最簡單的方法是使用帶有空氣壓力的高度計指示高度(本質(zhì)上是一個氣壓計)。但測量需要更高的精度。各種手段,如精密水準(zhǔn)測量(也稱為微分水準(zhǔn)),已經(jīng)開發(fā)出來。精密水準(zhǔn)測量,兩點之間的測量工作通過一系列儀器和水準(zhǔn)尺進(jìn)行。Triangulationisanothermethodofhorizontallocationwaswidelyusedinthepastyears.Aslongastheyarevisiblefromoneoftheoriginalobjects,withthetriangulationmethod,distancesanddirectionsbetweenobjectsatgreatdistancefromoneanothercanbedetermined.AmoremoderninstrumentisaTotalStation,whichisatheodolitewithanElectronicDistanceMeasurement(EDM).Sinceitsintroduction,totalstationhasmadethetechnologicalshiftfrombeingoptical-mechanicaldevicetobeingfullyelectronic。三角測量是過去被廣泛應(yīng)用的一種測量水平位置的方法。只要他們從最初的對象是可見的,三角測量方法,兩個較遠(yuǎn)物體之間的距離和方向可以確定。更現(xiàn)代的儀器是全站儀,它是一個經(jīng)緯儀與電子測距儀(EDM)的組合。全站儀引入以來,全站儀技術(shù)已經(jīng)從光學(xué)機械設(shè)備完全轉(zhuǎn)變?yōu)殡娮拥?。ModernTotalStationsnolongerrequireareflectororprism(usedtoreturnthelightpulses)tomeasuredistances,theyarefullyroboticandcanevene-mailpointdatatotheofficecomputer.Withtheadvancementofsatellitepositioningtechnology,thespeedandprecisionofsurveyingaregreatlyincreasedbyusingGlobalPositioningSystem(GPS).BecauseGPSsystemsdonotworkwellinareaswithdensetreecoverorconstructions,TotalStationsarestillusedwidelyalongwithothertypesofsurveyinginstruments.Nowrobotic-guidedTotalStationsallowsurveyorstogatherprecisemeasurementswithoutextrasurveyorstolookthroughandturnthetelescopeorrecorddata.現(xiàn)代全站儀不再需要一個反射器或棱鏡(用于返回光脈沖)來測量距離,他們完全自動化甚至可以以電子郵件的方式發(fā)送數(shù)據(jù)點到辦公室的電腦。隨著衛(wèi)星定位技術(shù)的開展,測量的速度和精度大大增加通過使用全球定位系統(tǒng)(GPS)。因為GPS系統(tǒng)在茂密的樹木覆蓋的地區(qū)或建筑密集區(qū)工作性能不好,全站儀仍與其他類型的測量儀器一同廣泛使用?，F(xiàn)在智能全站儀允許測量員在沒有額外的測量員進(jìn)行檢核、調(diào)整棱鏡和記錄數(shù)據(jù)的情況下，進(jìn)行精確測量。Chapter2DatumsofSurveying2.1Geoidandreferenceellipsoid2.2Mapprojection2.3Datumsandcoordinatesystem2.1Geoidandreferenceellipsoid大地水準(zhǔn)面和參考橢球面TheEarth’sphysicalsurfaceisarealityuponwhichthesurveyingobservationsaremadeandpointsarelocated.However,duetoitsvariabletopographicsurfaceandoverallshape,itcannotbedefinedmathematicallyandsopositionscannotbecomputedonitssurface.Itisforthisreasonthatinsurveysoflimitedextent,theEarthistreatedasflatandplanetrigonometryusedtodefineposition.地球的物理外表是一個測量觀測地形和放樣點位的真實外表。然而,由于其變化的地形外表和整體形狀,它不能按照數(shù)學(xué)方法定義,所以點位也不能在其外表計算。正是因為這一原因,在調(diào)查范圍有限的情況下,地球唄認(rèn)為是平的,平面三角用來定義點的位置。Iftheareaunderconsiderationisoflimitedextent,orthogonalprojectionofthisareaontoaplanesurfacemayresultinnegligibledistortion.Planesurveyingtechniquescouldbeusedtocapturefielddataandplanetrigonometryusedtocomputeposition.However,iftheareaextendedtoalargeareabeyondlimitationandtreatedasaflatsurfacetheeffectoftheearth’scurvaturewillproduceunacceptabledistortion.如果考慮到測區(qū)的面積是有限的,這一地區(qū)的正交投影在平面上可能產(chǎn)生的變形是可以忽略不計的。平面測量技術(shù)可以用來捕獲野外數(shù)據(jù)和平面三角測量用于計算點的位置。然而,如果測區(qū)面積擴大到超出一定限制的區(qū)域,被當(dāng)作一個平面，由于地球曲率的影響將產(chǎn)生不可接受的變形。Therefore,amathematicalmodeloftheearthisneededtorepresenthorizontalpositionsandelevationsonmaps.Assuch,itisnecessarytodefineamathematicalsurfacethatapproximatestotheshapeoftheareaunderconsiderationandthenfitandorientateittotheEarth’ssurface.Suchamathematicalsurfaceisreferredinsurveyingasa‘referenceellipsoid’.因此,需要地球的一個數(shù)學(xué)模型來表示地圖上點的水平位置和高度。因此,必須定義一個接近考慮區(qū)域的數(shù)學(xué)平面,然后擬合并定位到地球外表。這樣的數(shù)學(xué)外表在測量上被稱為參考橢球體。(1)GeoidSincethephysicalsurfaceoftheEarthcan’tbeusedasacomputationalsurface,ameansealevelsurfaceisinstinctivelytakenintoconsideration.Meansealevel(MSL)isdefinedastheaverageleveloftheoceansurfaceforallstagesofthetideafterlongperiodsofobservations.Byextendingtheearth’sMSLthroughthelandmass,anequipotentialsurfaceapproximatelyatMSLwouldbeformed.Suchasurfaceiscalledthe‘geoid’.大地水準(zhǔn)面因為物理地球外表不能被用作計算面,平均海平面是本能地考慮。平均海平面被定義為長時間觀察所有階段潮后的平均海平面。將地球的平均海水面擴展到大陸上,接近于平均海水面的等勢面大約會形成。這樣一個外表被稱為“大地水準(zhǔn)面”。ItcouldbeimaginedthatatrenchisdugacrossthecountrieslinkingtheAtlanticandPacificoceans.Ifthetrenchisfilledwithseawater,thesurfaceofthewaterinthetrenchwouldrepresentthegeoid.它可以想象,在各個國家挖的連接大西洋和太平洋的槽。如果槽充滿海水,槽里水的外表代表大地水準(zhǔn)面。Thusbydefinition,thegeoidisanequipotentialsurfaceoftheEarthgravityfieldthatmostcloselyapproximatesthemeanseasurface.Thegeoidisonlyatheoreticalsurface,whichisperpendicularateverypointtothedirectionofgravity.Theshapeofgeoidcanbeactuallymeasuredwhichisbasedongravitydatacollectedworldwide.因此根據(jù)定義,大地水準(zhǔn)面是一個最接近平均海水面的地球重力場的等勢面。大地水準(zhǔn)面只是一個理論外表,它上邊的每一個點垂直指向重力的方向。大地水準(zhǔn)面的形狀可以由在全球范圍內(nèi)收集的重力數(shù)據(jù)來計算。AlthoughthegravitypotentialiseverywherethesameandthesurfaceissmootherthanphysicalsurfaceoftheEarth,itstillcontainsmanyirregularitieswhichrenderitunsuitablemathematicallocationofplanimetricposition.TheseirregularitiesarethoughttobeduetomassanomaliesthroughouttheEarth.Thegeoidremainsimportanttothesurveyor,asitisthesurfacetowhichallterrestrialmeasurementsarerelated.雖然重力勢處處都是一樣的,重力勢外表比物理地球外表光滑,它還包含了許多不規(guī)那么的形狀使它呈現(xiàn)不適合數(shù)學(xué)平面位置的點位。這些不規(guī)那么形狀被認(rèn)為是由于在整個地球質(zhì)量異常引起的。對于測量員來說大地水準(zhǔn)面仍然是重要的,因為它是與所有陸地測量相關(guān)的外表。Asthedirectionofthegravityvectoriseverywherenormaltothegeoid,itdefinesthedirectionofthesurveyor’splumb-bobline.Thusanyinstrumentwhichishorizontalizedbymeansofaspiritbubblewillbereferencedtothelocalequipotentialsurface.ElevationsarerelatedtotheequipotentialsurfacepassingthroughMSL.Suchelevationsorheightsarecalledorthometricheights(H)andarethelineardistancesmeasuredalongthegravityvectorfromapointtotheequipotentialsurfaceasareferencedatum.因為重力的方向向量在大地水準(zhǔn)面上到處都是正常的,可以用它定義測量員的鉛錘線的方向。因此通過水準(zhǔn)氣泡整平的任何儀器將會引用到當(dāng)?shù)氐任幻妗８叱膛c穿過平均海水面的等位面有關(guān)。海拔或高度等被稱為正常高(H),它是一個重力位上的點到等勢面所測量直線距離來作為參考數(shù)據(jù)。(2)ReferenceEllipsoidTheellipsoidisamathematicalsurfacewhichprovidesaconvenientmodeloftheEarth,andcanbestmeettheneedsofaparticulargeodeticdatumsystemdesign.Itisrepresentedbyanellipserotatedaboutitsminoraxisandisdefinedbyitssemi-majoraxisandflattening.Althoughtheellipsoidisaconceptandnotaphysicalreality,itrepresentsasmoothsurfaceforwhichformulascanbedevelopedtocomputeellipsoidaldistance,azimuthandellipsoidalcoordinates.(2)參考橢球體橢球是數(shù)學(xué)的外表給地球提供了一個方便的模型,并能最好的滿足特定的大地基準(zhǔn)系統(tǒng)的需求設(shè)計。它是由橢圓旋轉(zhuǎn)短軸和被定義為它的長半軸和扁率。雖然橢球是一個概念,而不是現(xiàn)實的物理外表,它表示一個平滑的外表在上邊可以用公式計算大地距離,方位角和大地坐標(biāo)。Duetothevariableshapeofthegeoid,itisnotpossibletohaveaglobalellipsoidofreferenceforusebyallcountries.由于變量的形狀大地水準(zhǔn)面,不可能有一個全球所有國家使用參考橢球。Thebest-fittingglobalgeocentricellipsoidistheGeodeticReferenceSystem1980(GRS80),whichhasthefollowingdimensions:globalgeocentricellipsoidsemi-majoraxisa=is6378137.0m全球地心橢球semi-minoraxisb=is6356752.314mflatteningɑ=1：298.257全球最正確擬合的地球橢球是全球地心大地參考橢球系統(tǒng)1980(GRS80),參數(shù)如下:長半軸a=6378137.0米短半軸b=6356752.314米壓扁ɑ=1：298.257EquatorialAxisEquatorialAxisPolarAxisNorthPoleSouthPoleEquatoraba=6378137m北極

b=6356752.3m

equatorialdiameter=12756.3km

polardiameter=12713.5km

equatorialcircumference=40075.1km

surfacearea=510064500km2WGS[世界大地坐標(biāo)系統(tǒng)]84橢球:a=6378137mb=6356752.3m赤道直徑=12756.3公里極地直徑=12713.5公里赤道周長=40075.1公里面積=510064500平方公里Therelationshipofallthreesurfaceswhichareterrain,geoidandellipsoidisillustratedinthefigurebelow.地球外表、大地水準(zhǔn)面、參考橢球面三者之間的關(guān)系見下列圖。TheorthometricheightHistheheightwithreferencetotheMSL,whereasthegeodeticheighthistheheightreferencedtoellipsoid.正高H是參考面到平均海水面的高度,而大地高度h參考面到參考橢球的高度。Terrain地勢GroundpointA地面點ATerrain地勢GroundpointA地面點AHHhGeoidhGeoid大地水準(zhǔn)面BN=h-HBN=h-Hreferenceellipsoidreferenceellipsoid參考橢球面ThequantityN,theheightofthegeoidabovethereferenceellipsoidortheperpendiculardistancebetweenthegeoidandthereferenceellipsoidatapoint,isusuallycalledthegeoidalheight(geoidundulation).數(shù)量N,大地水準(zhǔn)面高于參考橢球體的高度或某點大地水準(zhǔn)面和參考橢球體面之間的垂直距離,通常被稱為大地水準(zhǔn)面高度(大地水準(zhǔn)面起伏)。Oncethegeoidisdetermined,thedifferencebetweenthesurfacesoftheellipsoidandgeoidanywhereinthecountrycanbecomputed.Surveyorsusedtoworkingwithspiritlevelhavereferencedorthometricheights(H)tothe‘a(chǎn)verage’surfaceoftheearth,asdepictedbyMSL.ThesurfaceofMSLcanbeapproximatedbythegeoid.一旦大地水準(zhǔn)面確定下來,在全國的任何地方都可以計算參考橢球面和大地水準(zhǔn)面之間的距離。測量員用水準(zhǔn)儀測量正高(H)也就是點到地球平均外表的高度,如平均海水面。平均海水面可以近似為大地水準(zhǔn)面。TheheightoftheMSLabovethegeoidiscalledtheseasurfacetopography(SST).Itisaverydifficultquantitytoobtainfromanymeasurements.Consequently,itisnotyetknownveryaccurately.平均海水面的高度高于大地水準(zhǔn)面的地方稱為海面地形(SST)。這是一個非常難以通過任何測量獲得的量。因此,它是還沒有完全確定。GPSheightsarereferencedtotheellipsoid,amathematicalmodelthatdoesnotphysicallyexist.Thismodel,doesnotagreewithMeanSeaLevel.ThatmeanstheheightofapointdeterminedfromGPSisnotthesameasitssealevelelevationasdeterminedbyleveling.GPS高是由參考橢球得到的,參考橢球是物理上不存在的數(shù)學(xué)模型。這個模型,與平均海平面不擬合。這意味著決定某點的GPS高與它的由水準(zhǔn)尺測得的平均海水面高程不一樣。Thesummaryoftherelationshipsamongheightsystemscanbeillustratedbelow:(1)MSLelevationisroughlyequivalenttoorthometricheight(H),thetechnicalnameforheightabovethegeoid.Thegeoidis,forallintentsandpurposes,thesameasMSL.高度系統(tǒng)之間的關(guān)系可以總結(jié)如下:平均海水面高度相當(dāng)于正高(H),是大地水準(zhǔn)面以上高度的專業(yè)名稱。大地水準(zhǔn)面是,從某種意義上,和平均海水面一樣的。(2)Geoidalheight(N)istheseparationbetweenthegeoidandtheellipsoid(sometimescalledGeoidalseparation).Itcanbeplusorminus.Anegativegeoidalseparationindicatesthatthegeoidisbelowtheellipsoid,andapositiveseparationisabove.(3)Ellipsoidalheight(h)isthedistanceaboveorbelowtheellipsoid(plusorminus).Ellipsoidalheightisalsocalledgeodeticheight.(2)大地水準(zhǔn)面高度(N)是大地水準(zhǔn)面和參考橢球面之間的差距(有時稱為大地水準(zhǔn)面差距)。它可以是正負(fù)。負(fù)的大地水準(zhǔn)面差距說明大地水準(zhǔn)面在參考橢球面之下,正的大地水準(zhǔn)面差距說明大地水準(zhǔn)面在參考橢球面之上。大地高(h)是高于或低于橢球的距離(正負(fù))。大地高也被稱為大地的高度。2.2Mapprojection地圖投影2.2.1Definitionofmapprojection地圖投影的定義MapprojectionsareattemptstoportraythesurfaceoftheEarthoraportionoftheEarthonaflatsurface.Somedistortionsofconformality,distance,direction,scale,andareaalwaysresultfromtheprocessofmapprojection.Someprojectionsminimizedistortionsinsomeofthesepropertiesatexpenseofmaximizingerrorsinothers.Sonoprojectioncanbesimultaneouslyconformalandarea-preserving.地圖投影是試圖描述地球的外表或地球的一局部放在平面上時的形狀。一些變形的保形性、距離、方向、比例尺、區(qū)域總是源于地圖投影的過程。一些投影減少局部特性的變形以增大其他地區(qū)的誤差為代價。所以沒有一種變形能同時具有保形性和保區(qū)域性。2.2.2Distortionsofmapprojection地圖投影變形Conformality:Whenthescaleofamapatanypointonthemapisthesameinanydirection,theprojectionisconformal.Meridians(linesoflongitude)andparallels(linesoflatitude)intersectatrightangles.Shapeispreservedlocallyonconformalmaps.保形性:當(dāng)?shù)貓D上任意一點兒地圖比例尺在任何時候在任何方向都是相同的,這種投影就是正形投影。子午線(經(jīng)度線)和平行線(緯度)相交成直角。形狀在映射地圖中被保存為原形。Distance:Amapisequidistantwhenitportraysdistancesfromthecenterofprojectiontoanyotherplaceonthemap.距離:地圖上任何一點到投影中心的距離是的等距的。Equidistantprojection,akindofarbitraryprojection,isreferredtothatthedistanceremainsconstantafterprojectedalongaspecificdirection,namelyalongthespecificdirection,thelengthratioisequalto1.Inthepracticalapplications,themeridiansareusuallyprojectedasstraightlines,andthedistancesalongalongitudinaldirectionaremaintainedequal,theanglesandareasaredistorted.Theequidistantprojectionisfrequentlyusedfordrawingtrafficmap.等距投影,一種任意投影,被稱為投影后沿特定的方向距離保持不變,即沿特定的方向,長度比率等于1。在實際應(yīng)用程序中,子午線通常投影為直線,并沿經(jīng)線方向保持相等的距離,角度和區(qū)域發(fā)生變形。等距投影經(jīng)常用于繪制交通地圖。Direction:Amappreservesdirectionwhenazimuths(anglesfromapointonalinetoanotherpoint)areportrayedcorrectlyinalldirections.Scale:Scaleistherelationshipbetweenadistanceportrayedonamapandthesamedistanceontheearth.Area:whenamapportraysareasovertheentiremapsothat