Chinese English

In PHOTOGRAPHY, the actual difference in DENSITY between the highlights and the shadows on a NEGATIVE or POSITIVE. Contrast is not concerned with the magnitude of DENSITY but only with the difference in DENSITIES. Also the rating of a photographic material corresponding to the relative density difference which it exhibits.

A system of points with established POSITIONS or ELEVATIONS, or both, which are used as fixed references in positioning and correlating map features. Control is generally classified in four orders (with first order denoting highest quality) according to the PRECISION of the methods and instruments used in establishing it, and the ACCURACY of the resultant POSITIONS and ELEVATIONS. Often calledbasic control. Regulation or direction of a machine, electronic equipment, etc.; or the DIAL, knob, switch, etc. for performing this function. The exercise of directing influence over the movements of a craft or missile, with particular reference to changes in direction and SPEED.

（1）已经建立位置或高程的点系统，用来作为确定地图要素的位置及相互关系的固定基准。根据它建立时所使用的方法和仪器的精度以及位置和高程的综合精度一般分为四个等级（一等质量最高）。通常称为基本控制。 （2）指对机器、电子设备等的调节或操控，或者执行这个功能的控制调节盘、旋钮、开关等。 （3）指对飞行器或导弹运动过程施加修正影响的过程，尤其指方向和速度变化的修正。

Points established by subordinate SURVEYS, to relate AERIAL PHOTOGRAPHS used in mapping with the system of GEODETIC CONTROL. The points must be positively photo-identified, that is, the points on the GROUND must be positively correlated with their IMAGES on the PHOTOGRAPHS.

A point on the ground whose position (horizontal and vertical) is used as a base for a dependent survey. Also referred to as control station.- 2. In photogrammetry, any point in a horizontal and vertical control system that is identified on a photograph and used for correlating the data shown on that photograph. More specific terms are photo-control point, picture control point and ground control point.

1.地面上的一点，其位置（水平和垂直位置）为相关测量的基础。也称为控制站。 2.在摄影测量中，指像片上可辨认的、用来把像片上显示的资料连接起来的平面和高程控制点。更进一步的规范术语是：photo-control point（像片控制点）、picture control point （图片控制点）、ground control point（地面控制点）。

In general, mass motions within a fluid resulting in TRANSPORT and mixing of the properties of that fluid. In the ATMOSPHERE, organized internal motions within a LAYER of air, leading to vertical transport of heat, momentum, etc.

In OCEANOGRAPHY, a situation whereby waters of different origins come together at a point or, more commonly, along a line known as a convergence line. Along such a line the denser water from one side sinks under the lighter water from the other side. See SINKING.