Background:
The Captain's Rutter is a logbook of all the known hazards and details of the local area. Captains who spend their time in one area will achieve a high level of detailed knowledge about the area that allows for superior navigation and strategy. Not just any ship captain can draw up the detailed map and measurements needed for a Rutter, only a knowledgeable mapmaker can produce a usable record of the terrain. The advantage gained by such a detailed book is so great that captains treasure the Rutter as an invaluable tool and guard it's contents with their life. Only the most trusted of companions will ever know where a captain keeps his or her Rutter and very few ever have the opportunity to copy it's contents into their own Rutter.
Description:
The Rutter would be a large book found in the Captain's log. Clicking on the Rutter brings up a map of Avonmora which allows you to click on any port to bring up a detailed map of that port divided into 256 regions (squares). The player can choose one square to explore for the next 24 hours (turns can speed up the process). Once explored the region adds +0.04% chance to hit in combat at that port and -0.1% travel time when departing that port. Once the 256 regions of the port are explored and written in the Rutter the total percent chance to hit is +10.24% and travel time is 25.6% shorter.
There are 2 other ways to acquire Rutter Logs:
1) A player can share explored regions with other players by selecting which regions to share and which player number.
2) Each battle won has a 20% chance of awarding 1 region to the attacker but only regions explored by the defender may be found by the attacker.
Once a region has been recorded in a player's Rutter it can never be lost, only copied by another player.
Here is a mock-up of what I imagine it would look like:

The blue squares of ocean are the explored ones and the paper-colored squares are unexplored. The player can choose which square to explore next and can choose which square to share with a target player. As the whole map gets explored it might to look like this:

Discussion:
I believe this feature would provide interesting depth to combat and trading and would benefit strong guilds who divide-and-conquer mapping the ports of Avonmora. It would be a prized posession for the guild officers who have received the information and might be a tool of betrayal for a nefarious soul...
New players who join a training guild might be rewarded for sharing their Rutter Logs with the guild officers and maybe some guilds might offer Rutter Logs to new players as a recruitment device. Within one year a guild could conceivably chart the entirety of Avonmora but the trust and loyalty required to keep the information secret would be difficult at best. Large traders may find it worthwhile to pay for Rutter Logs in ports where they require faster travel times. Pirates may find it easiest to plunder large traders who have collected many Rutter Logs in the ports where their ships travel. A particularly brash pirate may demand a trader pay tribute in the form of Rutter Logs.
256 regions x 21 ports is 5,376 total regions so one player acting alone would barely manage mapping 1.3 ports in a year without using turns. Thus cooperation, coercion and competition are encouraged. I have proposed that only 1 region can be explored per day per player because allowing any fleet to explore would mean a huge trader could explore everything within a month or two.
The detailed maps of each port would add a much needed visual aspect to the world of Avonmora. I have long wanted to see more detail of the world we sail and conquer.
Question:
Is +10.24% chance to hit and -25.6% travel time too much or too little? If the advantage of collecting Rutter Logs is not great then players will consider it a hassle and not bother with the feature. Are there other advantages that Rutter Logs should provide?
Should there be more than 256 regions per port?
Captain Dungeness