This cheat will reveal the entire map for you in single player.
Grand Theft Auto 5: Cheat (Singleplayer Reveal Map 1.1) Free Download
Activation / Deactivation on key 9
Installation
You need ScriptHookV, VC ++ Redistributable 2013 x64
Drop files gtamp-reveal-full-map.asi and gtamp_reveal_map_sp.cfg to the games
Good luck ^ _ ^