Early hydrographic surveys consisted of depths calculated by sounding pole and hand lead line, with positions based on three-stage sextant fixes to mapped reference factors. Direct lines have been ropes, or strains, with depth markings and direct weights hooked up. The increase of new Digital technologies – sidescan sonar and https://hydrographic-survey-in-ba72307.ivasdesign.com/53907044/the-greatest-guide-to-hydrographic-survey-in-bangladesh