水下测量是大地测量中地形测量的一部分。水面以上的陆地地形测量(用等高线表示)和水面以下的水底地形测量(一般用等深线表示)同属于地形测量,后者就是本文所述的水下测量。根据施测对象的内容,虽有海洋测量、航道测量、海道测量、疏浚测量、湖泊测量、河道测量等不同名称,但只是面积的大小,水的深浅不同而已,主要内容就是水下地形测量(简称水下测量)。 Underwater measurements are part of the geodetic survey in geodesy. Terrestrial measurements above the surface (indicated by contours) and those above the surface (commonly indicated by isobaths) are both terrain measurements, the latter being the underwater measurements described in this article. According to the contents of the test object, although there are different names such as ocean measurement, waterway measurement, seaway measurement, dredging measurement, lake measurement and river measurement, but only the size of the area and the depth of the water are different, the main content is underwater topographic measurement Referred to as underwater measurement).