As a member of the observer's books club, it's a pleasure to explain a little bit about the hydrographic survey and different methods to take accurate positioning in the water.
You should have basics of surveying to keep on understanding how it goes around.
Textbook referral: "Surveying (6th and 7th Edition)" by A. Bannister, Stanley Raymond, Raymond.
Civil Engineering
Sextant use: https://youtu.be/DrAkrgZRb9Y
float method: https://youtu.be/W1lUdxE5BGU
