Early hydrographic surveys consisted of depths measured by sounding pole and hand direct line, with positions determined by three-place sextant fixes to mapped reference points. Guide traces ended up ropes, or lines, with depth markings and direct weights attached. NOAA makes use of USCG-taken care of differential GPS beacons to https://edwinpsycd.ka-blogs.com/85806008/5-simple-statements-about-hydrographic-survey-in-bangladesh-explained