unit 8测量中的误差

Unit 8 Errors in Measurement （测量工作中的误差） Measurements are defined as observations made to determine unknown quantities. （测量被定义为确定未知量【quantity】的观测） They may be classified as either direct or indirect. （它们可以被分为直接观测和间接观测） A direct measurement is one where the reading observed represents the quantity measured, without a need to add, take averages or use geometric formulas to compute the value desired. （直接观测就是观测读数即代表了【represent代表、描述】测量量，不需要另外加、取平均或利用几何【geometric几何的】公式【formulas】来计算出所需【desired想得到的】值。） Determining the distance between two points by making a direct measurement using a graduated tape is an example of direct measurement. （用一把刻度尺直接确定两点之间的距离，就是一个直接观测的例子） An indirect measurement requires calculation and can be determined from its mathematical relationship to direct measurements when it is not possible or practical to make direct measurements. （间接观测需要计算，当直接观测是不可能或不实际【practical实际的】时 ，可以利用它与直接观测量之间的数学关系来确定。） For example, station coordinates can be mathematically computed by measuring angles and lengths of lines between points directly. （例如，测点【station测点】坐标可以由直接测得的点之间直线的角度和长度来计算） Therefore the indirect measurements (computed station coordinates) contain errors that were present in the original direct observations and propagated (distributed) by the computational process. （因此，这个间接测量值（计算出的测点坐标）包含了初始【original】直接观测出现【present】的和由计算过程传播【propagate】（散播的）的误差。）【that 后面全都是修饰errors的】 This distribution of errors is known as error propagation. （这种误差的散播被认为【be known as被称为】误差传播） Also, it is the indirect nature of measurements that forces the need to often apply some rather sophisticated mathematical procedures to analysis of errors and thus determine a “best value” to represent the size of the quantity. （同样，间接测量的特性需要【forces the need to使„„成为需要】经常应用一些更复杂的数学方法【procedure】来分析误差并从而确定“最佳值”来代替【represent代替、代表、扮演、表现】测量值的大小）

It can be stated unconditionally that all measurements, no matter how carefully executed, will contain error, and so the true value of a measurement is never known, and the exact sizes of the errors present are always unknown. 可以绝对地【unconditionally无条件地】说【state声明】，所有测量工作，无论多么仔细的实行【execute】，也会包含误差，因此测量的真值是永远不知道的，出现【present出现】的确切的【exact】误差大小也永远不知道 Even with the most sophisticated equipment, a measurement is only an estimate of the true size of a quantity. （即使使用最复杂精密的装置，测量值也仅仅是一个量的真值的估计【estimate】） This is because the instruments, as well as the people using them are imperfect, because the environment in which the instruments and people operate influences the process, and because the behavior of people, instruments, and the environment cannot be fully predicted. （这是因为同使用它们的人一样，仪器是不完美的【imperfect】，仪器和人的操作环境影响会观测过程，并且人的行为，仪器，和环境不能完全预知【predicte】） However, measurements can approach their true values more closely as better equipment is developed, environmental conditions improve and observer ability increases, but they can never be exact. （然而，当【as】仪器的改进，环境条件改善和观测者技术【ability】的进步时，测量可以非常接近它们的真值，但是它们永远不能达到真值） By definition, an error is the difference between a measured value for any quantity and its true value. （根据【By】定义，误差是某一量的测量值和它的真值之间的差值。） The sources of errors fall into three broad categories which are described as follows: （误差来源分成【fall into分成、属于、落入】三个主要的【broad】类型【category】，描述如下：）

Instrumental Errors.（仪器误差）These errors are caused by imperfections in instrument construction or adjustment. （这种误差由仪器的结构和调节装置不完整性引起） For example, the divisions on a theodolite or total station instrument may not be spaced uniformly. （例如，经纬仪或全站仪中的刻度【divisions，division原意指分离、分开，这里指刻度】没有被均匀地【uniformly】分划【即刻度分划不均】） These error sources are present whether the equipment is read manually or digitally. （不论是人工【manually人工地】读取还是数字式读取，这种误差源均会出现）

Natural Errors.（自然【环境】误差）These errors are caused by variation in the surrounding environment conditions, such as atmospheric pressure, temperatures wind, gravitational fields, and magnetic fields, etc. （这种误差是由周围环境条件的变化【variation】引起的，如大气压力，温度，风力，重力场，和磁场）

Personal Errors.（人为误差）These errors arise due to limitations in human senses, such as the ability to read a micrometer or to center a level bubble. （这种误差的出现【arise出现v.】是由于【due to 由于adv.】人类的感官局限性【limitation局限性】，比如读取千分尺和对中水平气泡的能力） The sizes of these errors are affected by personal ability to see and by manual dexterity. （这种误差的大小受到人眼观察能力和手的灵活性【dexterity灵活n.】的影响） These factors may be influenced further by temperature, insects, and other physical conditions that cause humans to behave in a less precise manner than they would under ideal conditions. （这种因素受温度、蚊虫【insect虫】和其它引起人不精确行为的自然条件的影响，使得操作者在这种环境中的行为精度较理想条件下更低）