Early hydrographic surveys consisted of depths calculated by sounding pole and hand direct line, with positions determined by 3-level sextant fixes to mapped reference details. Lead traces had been ropes, or strains, with depth markings and lead weights connected. Salinity together the Coastline differs with solid gradients. You can find https://hydrographicsurveyinbangl23069.suomiblog.com/new-step-by-step-map-for-hydrographic-survey-in-bangladesh-48121212