Chinese English

A straight rod or bar, designed for use in measuring a vertical distance between a point on the ground and the LINE OF COLLIMATION of a LEVELLING INSTRUMENT which has been adjusted to horizontal position. Also called levelling staff.

一种直杆或直棒，用于测量地面点和已调整至水平位置的水准仪照准线之间的垂直距离。也称为levelling staff（水准标尺）。

A surface which, at every point, is perpendicular to the DIREC­TION OF GRAVITY. A level surface is an EQUIPOTENTIAL SURFACE. The GEOID or, in general, any surface parallel to it, is a level sur­face. If changes in ELEVATION due to TIDES, WINDS, etc. are neglected, the surface of the SEA is a level surface. A level surface is not a plane surface, but it is sometimes so regarded in SURVEYS of limited areas.

每一点均垂直于重力方向的平面。水准面是一个等位面。通常大地水准面或者任何平行于它的面，即为水准面。如果忽略潮汐、风等对海面高度变化的影响，则海平面是一个水准面。一个水准面并不是一个平面，但在测量有限区域时可视为平面。

Motions of the MOON due to which certain margins round the MOON's LIMB occasionally pass out of view while a cor­responding margin on the other side comes into view. The librations enable 59 per cent of the MOON's surface to be seen at one time or another.

由于月球的运动，月球边缘某处偶尔看不见，而另一边相应的边缘却可看见。月视振动使月亮的59%在某一刻或另一时刻可见。

(LIght Detection And Ranging) An instrument that measures distance to a reflecting object by emitting timed pulses of LASER light and measuring the time between emission and reception of reflected pulses.  The measured time interval is converted to distance.  In survey use, the lidar system usually scans the light PULSEs across the TRACK of the SURVEY platform (usually an aircraft) so that successive PULSEs cover a SWATH(E) either side of the platform's track.  Infra-red LASERS will reflect off land and water, and are normally used for TOPOGRAPHIC lidar SURVEYs.  Blue-green LASERS will penetrate water and are used in HYDROGRAPHIC lidar SURVEYs.

（激光雷达）通过发射计时脉冲到反射目标并测定脉冲发射和接收之间的时间间隔来测量距离的仪器。测量时间间隔转换为距离。在测量中使用时，雷达系统通常在测量平台（通常为飞机）航迹线方向扫描光脉冲，这样连续脉冲会覆盖平台航迹线两侧的狭窄的条带。近红外激光会被陆地和水反射，通常用于地形激光测量。蓝绿激光能穿透水体，用在海道激光测量中。

A luminous or lighted AID TO NAVIGATION. For internationally agreed abbreviations of light characteristics see the International Chart Specifica­tions.

A flashing light in which a sequence of groups of one or more flashes, which are specified in number, is regularly repeated, and the groups comprise different numbers of flashes.

An occulting light in which a sequence of groups of one or more eclipses, which are specified in number, is regularly repeated, and the groups comprise different numbers of eclip­ses.