Can a number be accurate, but not very precise?（一个量可以正确却不怎么精确吗）
Let’s find out the difference between these two terms; you’ll see that precision and accuracy are really two different things.（让我们来找出这两个术语的不同；你将会看到精度和准确度确实是两个不同的概念）
A measurement can be precise but inaccurate, as well as accurate but imprecise.（一个测量量可以是精确的但不准确，也可以是准确的但不精确。）
For example, if a measurement was made with much care using a highly refined instrument, repeated readings of the same quantity wouldagree closely and thus precision would exist.（例如，如果一个测量量由仔细的利用高精密的【highly refined】仪器，对一个数重复读数得来，它们将非常一致，精度就存在了）
But if the instrument contained one or more undetected, uncorrected systematic errors, the results would be inaccurate.（但是如果仪器含有一个或多个未被发现、未被修正的系统误差，结果将不会准确的）
In contrast, it is possible that the mean of several repeated measurements of this same quantity, using a less refined (but calibrated) method,could be closer to the true value and thus this procedure would yield more accurate results even though there was less agreement among thereadings.（相反【In contrast】，这个量的几个重复测量值，用的是低精密的（但经过校正的）方法，可以更接近真值，这样，这个过程将产生【yield】更准确的结果，即使【even though】这些读数中【among在??之中】的一致性很低）
Perhaps the easiest way to illustrate the difference between accuracy and precision is to use the analogy of a marksman, to whom the “truth”represents the bull’s –eye.（或许最简单的举例说明【illustrate】准确度和精度之间不同方法是，用一个射手的座类比【analogy类比、推理】，“真”就代表了靶心【bull’s –eye】）
Precision: The degree of refinement in the performance of an operation, or the degree of perfection in the instruments and methods used toobtain a result, or an indication of the uniformity or reproducibility of a result.（精度：一项工作【operation】成绩【performance成绩、执行】的精密程度，或者获取结果的仪器和方法的完善【perfection完美、完善】程度，或者一致性【uniformity】程度的指标或结果的重复性【reproducibility重复能力】。）
Precision relates to the quality of an operation by which a result is obtained, and is distinguished from accuracy, which relates to the quality of the result.（精度涉及【relates to】获取结果的操作的质量，区别于【distinguished from区别于，disinguished卓越的】准确度——涉及结果的质量）
Figure 1 shows uniformity achieved by the marksman who is skilled by very small scatter.（图1显示了射手完成的一致性，非常熟练，分散【scatter分散n.】非常小）
It illustrates the excellent precision.（举例说明了极好的精度）
However, as the shots are far from the center, caused by the bent sight (systematic error), they are completely inaccurate.（然而，由于斜视（系统误差），子弹离中心很远，它们完全不准确）
With the knowledge gained by observation of the results, the marksman can apply a systematic adjustment (aim higher and to the left of hisintended target, or have his equipment adjusted) to achieve more accurate results in addition to the precision that his methodology andequipment have already attained.（由观察结果得出结论，这个射手可以采用系统的调整（相对于他瞄准的目标，再瞄高一些，向左一些，或者调整他的装备）来获得更准确的结果，来增加【addition增加n.】用他的方法和装备已经获得的精度）【这里的in additionto不是除??外的意思，in是介词，that 后面是precision的补语】
Such a situation can arise in practice when a piece of EDM equipment produces a set of measurements all agreeing to a few millimeters (highprecision) but, due to an operation fault and lack of calibration, the measurements are all incorrect by several meters (low accuracy).（这样的情形也出现在实际当中，当一个EDM装置测出一系列观测值都只相差几mm（高精度），但是由于【due to】操作失误和没有校正，测量值都有几米的偏差（低准确度）【incorrect不准确的adj. by后面表示程度】）
Accuracy: The degree of conformity of a final measured value, with respect to the true value as defined by accepted standard (the “truth”).（准确度：相对于【with respect to】被公认的标准（真理）【如三角形的内角和为180，这就是真理】定义的真实值，最终观测值的一致【conformity】程度）
Figure 2 shows the shots achieved by the marksman with a wide scatter.（图2显示了射手的子弹分散的很广）
It illustrates that the bent sight is now corrected, i.e. the systematic errors are minimized, and the marksman has approached the “truth”,although without great precision.（显示了现在斜视被修正，也就是说，系统误差最小化了，射手接近了“真值”，尽管精度不高） It may be that the marksman will need to change the equipment or methodology used to obtain the result if a greater degree of precision isrequired, as he has reached the limitations associated with his equipment and methodology.（如果要求更高精度的话，有可能射手需要更换获取结果的装备或方法，当他已经达到装备和方法所能达到的限度时）
In Figure 3, the shots are clustered near the center of the target.（在图3中，子弹集中于接近目标的中心） It represents results indicating both accuracy and precision.（它代表了结果显示出【indicate】准确度和精度）
In this case, the marksman has probably made one of the systematic adjustments that were indicated by his attainment of precision withoutaccuracy.（这种情况下【In this case】，射手或许做了一个系统调整——由他准确度不够的精度达到的【attainment达到n.】程度所显示【indicate】的那样）
The degree of precision has not changed greatly, but its conformity with the “truth” has improved over the results obtained in Figure 1. （精度并没有大的改变，但是它与“真值”的一致【conformity】已经超过图1中获得的结果了）
The scatter is, of course, due to the unavoidable random errors.（这些离散，当然，应归咎于【due to】不可避免的【unavoidable】随机误差）
So from the analysis of precision and accuracy, several important facts should be mentioned as follows.（因此从精度和准确度的分析看出，下列几点重要的事实需要提出：）
⑴Scatter is an “indicator of precision”; the wider the scatter of a set of results about the mean, the less reliable they will be compared withresults having a small scatter.（离散是一个“精度指标【indicator】”；一系列结果相对于平均值分散的越广，与离散小的结果比【comparedwith与??比】，它们越不可靠【reliable可靠的】）
⑵Precision must not be confused with accuracy; the former is a relative grouping without regard to the nearness to the truth, whilst the latter denotes absolute nearness to the truth.（精度不能和准确度相混淆；前者【the former】是不关心是否靠近真值的一个相关群）⑶Precisionmay be regarded as an index of accuracy only when all sources of error, other than random errors, have been eliminated.（只有当除了【otherthan除了】随机误差外，所有的误差原因【sources of error】已经被消除【eliminate】的时候，精度可以当作是准确度的指标）
An example that explains the difference between precision and accuracy better than any other in surveying has to do with error of closure intraversing.（测量上有一个比其它例子更好解释精度和准确度之间的不同的例子，与导线闭合差【closure闭合差】有关【have to do with与??有关】）
Many surveyors seem to think that error of closure checks the accuracy of the work.（许多测量者似乎认为闭合差检核的是工作的准确度）Wrong! Error of closure primarily checks the precision, not the accuracy.（不对！闭合差主要检核的是精度，而不是准确度）
It checks accuracy only in that it can find blunders. But, since it cannot detect systematic errors in the distances, it cannot fully checkaccuracy.（它检核准确度仅仅由于它能发现粗差。但是既然【since】它不能发现测距的系统误差，它就不能完全检核准确度） In surveying, the need for greater precision usually leads to greater costs.（测量上，高精度的需要通常导致高成本）
To obtain a higher degree of precision, it may be necessary to use more sophisticated (costly) equipment or a more time-consumingmethodology.（获得一个更高的精度，需要用更精密（昂贵的）的装置或更耗时的【time-consuming】方法）
The surveyor must determine what methodology and resultant precision is needed to achieve the accuracy required for a task at hand.（测量者应当决定什么方法和成果【resultant结果的】精度是完成手头上任务所要求达到的准确度所必需的）
Accuracy is telling the truth?Precision is telling the same story over and over again.（准确度表明了真实??精度一再地讲述现象【story有故事、谎话、情景的意思】）
Unit 18 Construction Layout （施工放样）
Engineering surveys are conducted to obtain data essential for planning, estimating, locating, and layout
for the various phases of construction activities or projects.（工程测量是在施工活动或工程的不同阶段中为计划编制、估计、定位、和放样获取必需的【essential必需的】数据的行为【conduct这里是动词：处理，翻译时用名词 行为 代替】）
After the necessary topographic maps are prepared and positions of the structures are established as well
as the final plans for the project are available, the engineers, architects or building contractors need to
know information about overall site grade and elevations to determine placement of site structures, or
estimate the volume of dirt to be moved, and then to set the required horizontal and vertical positions for
the structures.（在必要的地形图准备好、建筑物位置已确定之后，同样项目的最终方案也是可用的，工程师、建筑师【architect】或承建者【building contractor承建者、承包者；contract合同】需要知
道全部场地的坡度和高程来确定建筑场地的布置或者土方估算【volume体积；estimate估计】，然
后放置建筑物的设计【required要求的，这里指设计位置】水平和竖直位置）
Construction surveying is the translation of construction plans into physical points on the ground that can
be used as a basis for the actual construction.（施工测量【Construction surveying施工测量，不要翻译成建筑测量】是施工图【construction plan施工图】到地面上实地点位的转换【translation】，可以被用来作为实际施工的基础【或译为原理】。）
This type of surveying is sometimes called “construction layout” or “layout work”.（这种测量有时被称为“construction layout”或“layout work”）
Obviously construction surveying is the inverse operation of the activities with which the surveyor is
usually associated: the gathering of data regarding real points and positions on the ground and
representing those positions on a map.（显然施工测量【construction surveying】是测量者通常参与【associate参与、联合】的测量活动【activities】的逆过程【inverse operation逆过程；inverse反的】，这些通常的测量活动是实地点位数据的收集和那些位置在图上的表示）
The surveyor performing construction surveying is taking a “map” representing proposed structures and
placing that information on the ground.（进行施工测量的测量者持有一张标有【represent标示】设计建筑的“图纸”，并将其上的信息标定【place放置】在地面上）
As you can see, the surveyor is literally involved from start to finish of a construction project.（正如你所看到的，测量者从始至终【from start to finish自始至终】完全【literally完全地、真正地；原意是逐字地】伴随【involve伴随、涉及、包括】施工项目）
The results of construction surveying are seen in almost any urban, suburban, and even rural setting.（施工测量的成果能见于几乎任何城市的、郊外的、甚至乡村的工程【setting安置；这里译为工程】）
Almost any roadway, building, or other man-made structure probably had some amount of construction surveying involved. （几乎任何道路，建筑，或其它人工建筑物都大概有一些施工测量在内）
Construction surveying provides not only the horizontal location of new man-made structures, but also
the vertical information required to ensure that surfaces drain or pipes flow as required.（施工测量不只提供新人工建筑物的水平定位，还提供保证表面排水沟渠【drain】或管道【pipe】流动【flow】的竖向的信息）
Construction control: the first on-site job for the construction surveyor is to relocate the horizontal and
vertical control used in the preliminary survey.（施工控制：施工测量人员第一项场区内【on site场区内】的工作是重建初测【preliminary survey初测】时的水平和竖直控制）【即工程测量中的定测阶段的：恢复初测控制网】
Generally speaking, the horizontal and vertical control used in the preliminary survey may not be used again in construction surveying.（一般而言，初测的水平和竖直控制在施工测量中不再使用） Depending on the size and complexity of the project as well as the precision requirements, it may be
necessary to reestablish the horizontal and vertical control in the areas of proposed construction.（依靠工程的大小和复杂性以及设计精度，必然【necessary必然的】可以在设计【proposed计划的、被提议的】建筑物所在场地重建水平和竖直控制）
For example, the construction surveyor will establish one or more benchmarks in the general vicinity of
the project.（例如，施工测量人员将在大体【general】临近工程附近【vicinity临近，附近n. in the vicinityof 在附近】建立一个或多个水准点） These benchmarks are placed away from the immediate vicinity of the buildings so they will not be
destroyed by the construction operations, and are used to provide vertical control for the project.（这些水准点被设置在离建筑物较远的地方【away from远离；immediate vicinity紧靠n. 直接译为：离建筑物较远】，以免它们被施工工作【operation工作、操作】破坏，并用来提供工程的竖直控制）
Once these are set, the surveyor will then establish a good many less permanent but more accessible
benchmarks quite close to the project.（一旦这样，测量人员将建立一个很多【a good many很多】非永久的【permanent永久的】但是更易接近【accessible易接近的】于工程项目的水准点）
The location of these less permanent points should be carefully selected so that turning points will ideally
not be needed when elevations have to be set at the project.（这些非永久的点位应当谨慎选取，以保证在对工程高程放样时尽量【ideally完美地、理想地】不需转点【turning point】）
Such careful selection of the points may result in critical time saving which is so important on
construction project.（这些点的这种谨慎的选择，将会带来【result in导致，不符合中文习惯】关键的【critical批评的、危急的，可这里的意思是关键性的，即节省时间是关键性的】时间的节省，这在工程的施工工作【construction project】中非常重要）
Layout: It is obviously critical for a construction job that the various parts of the structure be placed at
the desired elevation.（放样：这明显是施工工作中的关键【critical关键的；或者：这明显对于施工工作来说是关键的】，建筑物的不同部分将放置【测设】到设计高程上去）
To accomplish this goal the construction surveyor will establish the reference lines or base lines before
the actual layout measurements begins.（为了完成这个目的，在实地放样测量开始之前施工测量人员将建立参考线或者基线）
For large construction projects, the usual procedure is to set down a main base line down the centerline of
the structure, such as the centerline of the bridge.（对于大型施工项目，通常的【usual】做法【procedure程序】是将主基线设到建筑物的中心线位置【即，以建筑物中心线为主基线】【set??down放下、设下】，例如桥中轴线）
The monuments are set along the centerline at each end beyond the area of the construction work.（沿中心线在越过施工场地两端设置标石）【还是沿中心线设置标石，中心线两端越过施工场地（沿中心线设置标石，直至越过场地）？】
The monuments along the ends of the line may be occupied by the surveyor and will enable him to check
and reset points within the construction areas.（测量者占据【occupy】基线两端的标石，使得他可以检查和重现放置施工场地内的点）
The stakes and points set during the process of construction surveying are not usually set at the actual
construction point, but usually on some sort of offset.（在施工测量过程中，所设的测桩和点位通常不在真实建筑点上，而是通常多少有些【some sort of】偏移【offset】）
This is done so that the survey stake is not disturbed by excavation or other activities that will take place at the actual point of construction.（这么做是为了让测桩不受挖掘或其它在真实建筑点上会发生的活动的干扰）
The stakes are marked with an “offset” and a “grade”, which provides the construction crew with the
special relationship of the construction stake to the actual point of construction.（测桩偏心设置【offset平移 grade斜坡，指的是两种后果，直接译为 偏心】，给施工人员提供额外的【special额外的、特殊的】施工桩和实际建筑点之间的关系）
The “offset” is the distance from the survey stake to the horizontal position of the actual point of