测绘英语第一单元调查的可靠性与误差

AmericanCongressonSurveyingandMapping(ACSM),isthescienceandartofmakingallessentialmeasurementstodeterminetherelativepositionofpointsorphysicalandculturaldetailsabove,on,orbeneaththesurfaceoftheEarth,andtodepicttheminausableform,ortoestablishthepositionofpointsordetails.commonlypracticedbysurveyors.Abasictenetofsurveyingisthatnomeasurementisperfect,andthattherewillalwaysbeasmallamountoferror.Surveyerrorsareclassedintothreetypes:Grosserrorsorblunders:areerrorsmadebythesurveyorduringthesurvey,forexample,upsettingtheinstrument,misaimingatatarget,orwritingdownameasurementwrong.Alargegrosserrormayreducetheaccuracytoanunacceptablelevel.Thereforesurveyorsuseredundantmeasurementsandindependentcheckstodetecttheseerrorsearlyinthesurvey.Systematicerrors:areerrorsthatfollowaconsistentpattern.ExamplesincludeeffectsoftemperatureonachainorEDMmeasurement,orapoorlyadjustedspirit-levelresultinginamisalignedinstrumentortargetpole.Systematicerrorsthathaveknowneffectscanbecompensatedorcorrected.Randomerrors:Randomerrorsarethesmallunavoidablemeasurementscausedbyimperfectionsinmeasuringequipment,eyesightandconditions.Theycanbeminimisedbyredundancyofmeasurementandavoidingunstableconditions.Randomerrorstendtocanceleachotherout,butchecksmustbemadetoensuretheyarenotpropagatingfromonemeasurementtothenext.Surveyorsusetoolssuchastotalstations,robotictotalstations,GPSreceivers,prisms,3Dscanners,radios,handheldtablets,digitallevels,andsurveyingsoftware.Adjustmentofobservationsisamodelforthesolutionofanoverdeterminedsystemofequationsbasedontheprincipleofleastsquares.Itisusedextensivelyinthedisciplinesofsurveying,geodesy,photogrammetry(thefieldofgeomatics,collectively).Therearethreeformsofadjustmentofobservations:parametric,conditional,andcombined.Inparametricadjustment,onecanfindanobservationequationh(X)=YrelatingobservationsYexplicitlyintermsofparametersX(leadingtotheA-modelbelow).Inconditionaladjustment,thereexistsaconditionequationg(Y)=0involvingonlyobservationsY(leadingtotheB-modelbelow),withnoparametersXatall.Finally,inacombinedadjustment,bothparametersXandobservationsYareinvolvedimplicitlyinamixed-modelequationf(X,Y)=0.Clearly,parametricandconditionaladjustmentscorrespondtothemoregeneralcombinedcasewhenf(X,Y)=h(X)-Yandf(X,Y)=g(Y),respectively.Yetthespecialcaseswarrantsimplersolutions,asdetailedbelow.Oftenintheliterature,YmaybedenotedL.Themethodofleastsquaresisastandardapproachtotheapproximatesolutionofoverdeterminedsystems,i.e.,setsofequationsinwhichtherearemoreequationsthanunknowns."Leastsquares"meansthattheoverallsolutionminimizesthesumofthesquaresoftheerrorsmadeintheresultsofeverysingleequation.Themostimportantapplicationisindatafitting.Thebestfitintheleast-squaressenseminimizesthesumofsquared

residuals,aresidualbeingthedifferencebetweenanobservedvalueandthefittedvalueprovidedbyamodel.Whentheproblemhassubstantialuncertaintiesintheindependentvariable(the'x'variable),thensimpleregressionandleastsquaresmethodshaveproblems;insuchcases,themethodologyrequiredforfittingerrors-in-variablesmodelsmaybeconsideredinsteadofthatforleastsquares.Leastsquaresproblemsfallintotwocategories:linearorordinaryleastsquaresandnon-linearleastsquares,dependingonwhetherornottheresidualsarelinearinallunknowns.Thelinearleast-squaresproblemoccursinstatisticalregressionanalysis;ithasaclosed-formsolution.Aclosed-formsolution(orclosed-formexpression)isanyformulathatcanbeevaluatedinafinitenumberofstandardoperations.Thenon-linearproblemhasnoclosed-formsolutionandisusuallysolvedbyiterativerefinement;ateachiterationthesystemisapproximatedbyalinearone,andthusthecorecalculationissimilarinbothcases.Unit1

TheReliabilityofaSurveyandErrorsNew

WordsandExpressionsreliability[rilai[5biliti]n.

可靠性error[5er[]n.

误差，错误issubjectto：受影响的accuracy[5Akjur[si]

n.

精度（有时特指最后结果的精度）accuracyrequired：要求的精度thescaleoftheplot：绘图比例尺plottableerror：绘图误差draughtsman[5drAftsm[n]n.

制图员，绘图员represent[repri5zent]vt.

表现，描绘，象征plottabledistance：可绘距离specification[spesifi5keiF[n]n.

规格，规范，技术要求，技术条件；说明书，明细表tolerance[5tCl[r[ns]n.

限差，容许误差；公差standard[5stAnd[d]n.

标准，规范angle[5ANg[l]n.

角，角度distance[5dist[ns]n.

距离，长度，间距salient[5seili[nt]a.

易见的，显著的，突出的，跳跃的blunder[5blQnd[]n.

粗差，错误grosserror：粗差transpose[trans5p[uz]vt.

vi.

改变顺序，互换位置well-planned：精心设计的observingprocedure：观测程序systematicerror：系统误差expansion[ik5spAnF[n]n.

扩充，膨胀frequency[5fri:kw[nsi]n.频率，周期，发生次数ElectromagneticDistanceMeasuring(EDM)：电磁测距仪collimation[kCli5meiF[n]n.

瞄准consist

of：包括succession[s[k5seF[n]n.

连续，演替level(l)ing[5lev[liN]n.

水准测量；抄平，置平traverse[5trAv[:s]

n.导线，导线测量；v.

横移，交叉traversing[5trAv[:siN]v.导线测量neglected[nig5lektid]a.被忽视的resultin：导致eliminate[i5limineit]vt.

排除，消除correction[k[5rekF[n]n.校正，修正，；修正量，改正数instrument[5instrum[nt]n.仪器，器械，器具，工具；手段，方法randomerror：随机误差，偶然误差identical[ai5dentik[l]a.一致的，同样的normally

distributed：正态分布的normaldistribution：正态分布dealwith：安排，处理，涉及accumulationoferror：误差累积workingfromthewholetothepart：从整体到局部redundant

observations：多余观测triangle[5traiAngl]n.三角形precision[pri5siV[n]n.精确，精密度，精度independent[indi5pend[nt]a.独立的inspect[in5spekt]vt.

检查，视察NotestotheText1．Agooddraughtsmancanplotalengthtowithin0.25mmandso,ifaplanofanareaisrequiredatascaleof1/1000,i.e.,1mmontheplanrepresents1montheground,thesmallestplottabledistanceis0.25m.Thus,forasurveyat1/1000scale,allthemeasurementsmustbetakensuchthattherelativepositionsofanypointwithrespecttoanyothermustbedeterminedto0.25morbetter.译文：一个好的绘图员可以在大约0.25mm的范围内画图，假如一个地区的图纸比例尺要求是1/1000，即1mm图上距离代表1m实地距离，那么最小的测距应该是0.25m。因此，对于1/1000比例尺的测量，所有测量必须保证任意一点与其他任意点的相对位置不得大于0.25m。2．Thereareseveraltypesoferrorthatoccurandaknowledgeoftheirimportanceandcharacteristicsisessentialintheunderstandingofthelimitationsofthetechniquesofmeasurement.Thesalientfeatureswillbestatednowbutfurtherinformationisgiveninlaterchapters.译文：在测量中有几种类型的误差，掌握它们的重要性和特性对于理解测量技术的限差是十分必要的。本章主要讲解这些误差的主要特征，其后的章节会对它们做更深入的阐述。3．Theseerrorsareofvitalimportanceinactivitieswhichconsistofaddingtogetherasuccessionofindividualobservations(seesectionsonlevelingandtraversing).Ifalltheindividualmeasurements