Chinese English

The general lowering in level of a moving vessel, relative to what its level would be were it motionless. Settlement is due to the regional depres­sion of the surface of the water in which the ship moves. It is not an increase in displacement. Settle­ment is a factor to be reckoned in ECHO SOUNDING.

运动船只水平的普遍下沉，这种沉降是相对于其静止时的水平线而言。船体坐沉的原因是由于船所行驶水面的局部压力，而不是实际吃水量增加造成的。在回声测深中，船体坐沉是一个要考虑的误差改正因素。

An angular division whereby a circle is divided in 360 equal parts called degrees. A degree is divided in 60 minutes and one minute in 60 seconds.

A double-reflecting instrument for measuring angles, primarily ALTITUDES of CELESTIAL BODIES. The sextant has an arc of 60°, a sixth of a circle, from which it derives its name, and a RANGE of 120°. In modern practice the term also applies to a similar instru­ment, regardless of its RANGE. See also OCTANT, QUADRANT and QUINTANT.

双反射型光学测角仪器。主要用于观测天体高度。其分度弧长为圆周长的六分之一，即60°，因此得名。六分仪测角范围为120°。现在，这个名称也用于一种不考虑测角范围的类似仪器。

(British terminology). A simplified and more robustly constructed version of the marine sextant intended primarily for use in HYDROGRAPHIC SURVEY. It has no SHADES, a wide angle low magnification telescope and is generally graduated in MINUTES of arc. It may be fitted with either a VERNIER or a MICROMETER reading device. Both mirrors are silvered all over to enable angles up to 180° to be measured. Some sounding sextants have a 90° prism attachment which reflects the normal direct LINE OF SIGHT 90° to the left. Called surveying sextant, or hydrographic sextant in U.S. terminology.

一种主要供海道测量使用的，结构简单且坚固的航海六分仪，没有遮光罩，有一个广角、低倍率放大望远镜，其圆弧刻度一般以分为单位。常配有游标或测微装置。两个镀银反射镜可使量测角度达到180°。一些水深测量六分仪装有90°角棱镜，用以反射90°法线视准线至左侧。美国术语称作surveying sextant, 或 hydrographic sextant 。

绘有多组相交曲线的一种测量图板。图板上的每条曲线相当于两站间某一角度的轨迹。在海道测量中使用这种图板不用分度规就可标出定位点。其方法是先用内插法在曲线之间求出每一测角所对应的轨迹，然后在两轨迹的交点处标出船位。以前称为六分仪定位图板。亦见fixed angle plot（定角标示法）。

A substitute for PLANE TABLE TRA­VERSE for short distances in unimportant areas where the use of the PLANE TABLE is impracticable and the survey party operates in a LAUNCH. AZIMUTH is carried forward by means of angles accurately measured with a SEXTANT. Distance is determined by measuring, also with the SEXTANT, the small horizontal angle between fixed TARGETS on a special rod held horizontally. The angle may be converted into a distance by means of a HYPSO­GRAPH.

在无法使用平板仪的一般区域，用以代替短距离平板仪导线的一种测量方法。测量员在汽艇上作业，用六分仪精确测角的方法进行方位角传递。距离也是用六分仪测定的，其方法是观测一个水平放置的特制标杆上俩固定目标间的小水平角，再用测高仪把角度转换为距离。

A coloured glass that can be moved into the LINE OF SIGHT of an optical instru­ment, such as a SEXTANT, to reduce the intensity of light reaching the eye. Also calledshade glass. See HORIZON SHADE, and INDEX SHADE.

可以放进光学仪器（如六分仪）视准线，用以减少到达眼睛光强的一种有色玻璃。参见horizon shade（调色镜），index shade（遮光镜）。

可以放进光学仪器（如六分仪）视准线，用以减少到达眼睛光强的一种有色玻璃。参见horizon shade（调色镜），index shade（遮光镜）。