Early hydrographic surveys consisted of depths measured by sounding pole and hand guide line, with positions based on a few-place sextant fixes to mapped reference points. Lead traces have been ropes, or lines, with depth markings and lead weights connected. Once analyzed, the location might be marked on Particular charts. https://hydrographic-survey09504.ltfblog.com/31517092/5-essential-elements-for-hydrographic-survey-in-bangladesh