求翻译：在船中吃水标识“4M”下边缘位置作为基准点，用钢尺倒挂在外板上，钢尺“0”刻度对齐基准点，保持钢尺的垂直，用激光经纬仪读数是什么意思？

The location of the logo "4m" under the edge of the drinking water in the boat as a reference point outside the board upside down with steel ruler, steel ruler "0" scale alignment reference point, to maintain the vertical ruler, using a laser theodolite readings

In the Ship waterline M ID " 4" the Edge as a reference point, with a steel ruler down on the plate, steel " 0" scale alignment reference points to keep the vertical ruler, laser theodolite, reading

Drinking water marking “4M” the lower limb position takes the reference point in the ship, hangs upside down with the steel rule on the outside plank, the steel rule “0” the scale division to the uneven reference point, maintains the steel rule vertically, with laser altazimuth reading

In ship draught identifies "4M" position the bottom edge as the datum point, with a ruler hung upside down on the outer panel, ruler "0" scale snap to datum points, keeping the vertical ruler, with a laser theodolite readings

正在翻译，请等待...