Chinese English

指经过指标差、俯角（眼睛的高度）和半径（仅对太阳和月亮）改正后的天体六分仪高度。也称作rectified altitude（视高度）。

在天文学中，指某一天体相对地球中心的位置。该位置不同于考虑折射、周日光行差和周日视差影响的天体观测位置。

The seaward limit of marine vegetation, such as mangrove, marsh grass, or trees in water that would reasonably appear to the mariner from a distance to be the fast shoreline. The seaward limit of kelp, low grass in water, and other low‑lying vegetation normally does not constitute an apparent shoreline. A line drawn on the chart in lieu of the mean high water line or the mean water level line in areas where either may be obscured by marsh, mangrove, cypress, or other type of marine vegetation. This line represents the intersection of the appropriate datum with the outer limits of vegetation and appears to the navigator as shoreline.

海洋植物群（如红树林、沼泽草、水中树木）的向海界线，这些植物使在一定距离上的航海人员看来认为是一种可靠的海岸线。大型海藻、低矮水草以及其它一些低矮植物的向海界限一般不构成视海岸线。在一些可能被沼泽地、红树、柏树或其它海洋植物遮蔽的海区，在海图上绘制一条线以代替平均高潮线或平均海平面线。这条线是近似基准面与植被外缘的交线，航海者可视作岸线。

A position that is considered to be less than third-order accuracy, but is generally considered to be within 100 feet (30.5 metres) of its correct geographic location. The method of location may be an indication of the recorded accuracy.

1. A gently dipping featureless surface, underlain primarily by SEDIMENT, at the base of any steeper SLOPE. 2. The area of wharf or quay for handling cargo. 3. A sloping underwater extension of an iceberg. 4. An outwash plain along the front of a glacier.

1.海底较陡斜坡基底处平缓的斜面，主要由沉积物形成。 2.码头或堤岸装卸货物的区域。 3.冰山向水下倾斜延伸的部分。 4.在冰川前方的沉积平原。

太阳或其它天体在地平上下运行的视弧的统称。在地平上的视弧称为周日弧，在地平下的视弧称为夜间弧。