【正文】 （換度盤(pán)方向至盤(pán)右并照準(zhǔn) C 點(diǎn)，記下讀數(shù)為 255 度）⑸Release upper p。) =50176。（水平角就是兩個(gè)方向值的差值，即， (75176。25176。.（著手，說(shuō)【示意】，“盤(pán)左”，【用豎絲】將 B 點(diǎn)的目標(biāo)仔細(xì)分中，水平 度盤(pán)讀數(shù)為 25 度）⑵The upper plate clamp is released and telescope is turned clockwise to survey point C. The readingon horizontal circle is 75176。 in a clockwise manner set in horizontal and vertical plane.（經(jīng)緯儀的水平度盤(pán)和豎直度盤(pán)與順時(shí)針刻【graduate】了 0 到 360 度刻劃的圓分度器【circular protractor】相連）The horizontal circle is used when measuring or laying off horizontal angles and the vertical circleis used to measure or lay off vertical angles or zenith angles.（測(cè)或撥水平角時(shí)用水平度盤(pán)，測(cè)或撥豎直角或天頂距時(shí)用豎直度盤(pán)【lay off 翻譯為撥、放樣的意思】）Usually the units of angular measurement employed in practice are degrees, minutes, and seconds, thesexagesimal system.（通常角度測(cè)量法【angular measurement 角度測(cè)量法】使用的單位是六十進(jìn)制【sexagesimal 六十進(jìn)制的】的度、分、秒）Angle Measurement （角度測(cè)量）A horizontal angle in surveying has a direction or sense。 minus the vertical angles.（顯然，天頂距等于 90 度減去豎直角）Vertical angles or zeniths are used in the correction of slope distance to the horizontal or in heightdetermined.（豎直角或天頂距用于斜距化平距的改正或者高程的測(cè)量）For the most part, the instrument used in the measurement of angles is called a transit or theodolite,although angles can be measured with clinometers, sextants (hydrographic surveys), or passes.（在極大程度上【for the most part】，用來(lái)測(cè)角的工具被稱(chēng)為經(jīng)緯儀，雖然角度可以用傾斜儀【一種測(cè)量物體 隨時(shí)間的傾斜變化和鉛垂線隨時(shí)間變化的儀器】、六分儀（用于海道測(cè)量）、或羅盤(pán)儀來(lái)測(cè)）The theodolite contains a horizontal and vertical circles of either glass or silver.（經(jīng)緯儀有一個(gè)玻璃的或鍍銀的水平度盤(pán)和豎直度盤(pán)）The horizontal and vertical circles of theodolite can be linked to circular protractors graduated from0176。 and 180176。）The zenith is an angle measured in a vertical plane downward from an upward directed vertical linethrough the instrument.（天頂距是一個(gè)在豎直面內(nèi)從一個(gè)過(guò)儀器的被定向?yàn)橄蛏系呢Q直方向線 向下測(cè)量的 角。90176。】）A vertical angle is an angle measured in a vertical plane which is referenced to a horizontal lineby plus (up) or minus (down) angles, or to a vertical line from the zenith direction.（豎直角是在一個(gè)豎直面內(nèi)參考于【reference 參考】水平線的正（仰）角或負(fù)（俯）角，或者相對(duì)于一個(gè)天頂方向的垂線的 角）Plus and minus vertical angles are sometimes referred to as elevation or depression angles, respectively.（正負(fù)豎直角有時(shí)分別【respectively 分別地】被稱(chēng)為仰角【elevation angle】或俯角【depression angle】）A vertical angle thus lies between 0176。）A horizontal plane at a point is the plane that is perpendicular to the vertical line at the point.（過(guò)一點(diǎn)的水平面是垂直于過(guò)該點(diǎn)的垂線的平面）There is only one horizontal plane through a given point.（過(guò)給定的一個(gè)點(diǎn)只有一個(gè)水平面）A vertical plane at a point is any plane that contains the vertical line at the point.（過(guò)一點(diǎn)的豎直面是包含【contain】過(guò)該點(diǎn)的垂線的任一平面）There are an unlimited number of vertical planes at a given point.（過(guò)給定的一點(diǎn)有無(wú)數(shù)個(gè)豎直面）Horizontal Angle and Vertical Angle（水平角和豎直角）A horizontal angle is the angle formed in a horizontal plane by two intersecting vertical planes, ora horizontal angle between two lines is the angle between the projections of the lines onto a horizontalplane.（水平角是指在一個(gè)水平面內(nèi)由兩相交【intersect 相交 v.】的豎直面形成的角，或者說(shuō)，兩條線之間的 水平角是這兩條線在水平面上的投影線的夾角）For example, observations to different elevation points B and C from A will give the horizontal angle∠bac which is the angle between the projections of two lines (AB and AC) onto the horizontal plane.（例如，在 A 點(diǎn)觀測(cè)不同高度的 B 和 C 點(diǎn)，其水平角∠bac 是由 AB 和 AC 兩條線在水平面上的投影構(gòu)成的） It follows that, although the points observed are at different elevations, it is always the horizontalangle and not the space angle that is measured (Figure 1).（由此得出結(jié)論【It follows that 由此得出結(jié)論】，雖然被觀測(cè)的點(diǎn)在不同的高度上，測(cè)出的總是水平角而不是空間角。）A horizontal line at a point is any line that is perpendicular to the vertical line at the point. （一點(diǎn)上的水平線是垂直【perpendicular 垂直的】于過(guò)該點(diǎn)的垂線的直線。）More plete EDM instruments also have the capability of measuring horizontal and vertical or zenithangles as well as the slope distance. （更完全的【功能更完備的】EDM 還具有測(cè)水平角、豎直角和 天頂角的功能）These instruments referred to as total station instruments. （這種儀器被稱(chēng)為全站儀）Unit 4 Angle and Direction Measurement（角度和方向測(cè)量）Horizontal and vertical angles are fundamental measurements in surveying.（水平角和豎直角是測(cè)量的 基本測(cè)量工作）It is necessary to be familiar with the meanings of certain basic terms before describing angle anddirection measurement.（在描述角度和方向測(cè)量之前，有必要熟悉【be familiar with 熟悉】幾個(gè)【certain 某些】基本術(shù)語(yǔ)的含義【meaning】）The terms discussed here have reference to the actual figure of the earth.（這里討論的這些術(shù)語(yǔ)與地球的真實(shí)形狀有關(guān)【have reference to 與??有關(guān)】）Basic Terms（基本術(shù)語(yǔ)）A vertical line at any point on the earth’s surface is the line that follows the direction of gravityat that point.（地球表面任一點(diǎn)的垂線是指這點(diǎn)上沿著重力的方向的線【可譯為：地球表面任一點(diǎn)的垂線方向 是過(guò)該點(diǎn)的重力方向】）It is the direction that a string will assume if a weight is attached at that point and the stringis suspended freely at the point. （如果在這點(diǎn)上用線懸掛一個(gè)重物，當(dāng)線自由【即無(wú)干擾】靜止【suspended 暫停的、懸浮的】時(shí)，這條線所呈現(xiàn)【assume 呈現(xiàn)】的方向即重力方向。 (2)Light wave systems with range up to 5 km (for small machines), visible light, lasers and distance reduced by visibility。）These velocities, which are affected by the air’s density, are reduced and need to be recalculated in theatmosphere. （它們的速度，由于會(huì)收到空氣密度的影響而降低，在大氣中需要重新計(jì)算【recalculate】） The basic principle of EDM instruments is that distance equals time multiplied by velocity.（EDM 的基本原理是距離等于時(shí)間乘速度）Thus if the velocity of a radio or light wave and time required for it to go from one point to another are known, the distance between the two points can be calculated.（這樣，如果無(wú)線電波或光波的速度和其 從一點(diǎn)到另一點(diǎn)所需的時(shí)間已知了，兩點(diǎn)之間的距離就可以計(jì)算出來(lái)）The EDM instruments may be classified according to the type and wavelength of the electromagnetic energy generated or according to their operational range.（可以依照產(chǎn)生【generate】的電磁能量【電 磁波】的類(lèi)型和波長(zhǎng)或根據(jù)它們的運(yùn)作范圍【工作范圍】給 EDM 分類(lèi)。）EDM instruments refer to the distance measurement equipments using light and radio waves. （EDM 是利 用光波和無(wú)線電波測(cè)距的設(shè)備【refer to 譯為“是”】）Both light waves and radio waves are electromagnetic.（光波和無(wú)線電波都是電磁波【electromagnetic 電磁的】）They have identical velocities in a vacuum (or space) to 299,177。）The advent of EDM instrument has pletely revolutionized all surveying procedures, resulting i