Get Gangzone co ordinates without a tool?

hi everybody today i was working on a game Mode which isn't in San andreas, but far in the ocean so i cannot take gangzone co-ordinates by any tool,

i wanted to know if it's possible to make a gangzone there by taking co-ordinates /save ...
I'am sure it requires maths knowledge Mine is shit i'am just a 14 years old guy i only learned basic shits from school

Thanks in advance !