Odd ship-of-the-line movement

[Jabba]

In my present game, I was very surprised to see that my AI opponent, Germany, had a ship-of-the-line with a movement allowance of 4.

Mine have a movement range of 3, which is also what is stated in the Civipedia.

Also, it looks like the ship-of-the-line in question magically upgraded from a frigate (which is what was occupying the same tile on the previous turn). Is that possible? Is it some kind of AI cheat? A bug?

 

[King Kalmah]

I do recall the first nation to circumnavigate the globe gets a +1 movement bonus.

As for the upgrade not sure if I ever seen an AI upgrade a unit,but I bet they have to....

 

[Tlalynet]

AI upgrades like mad, they even get sharp discounts on upgrade costs at higher levels.

If a Frigate can upgrade to a SOTL they'd do it. I'm not sure weather they can though...

 

[Verarde]

The extra movement is likely from the circumnavigation.

Frigates upgrade to Destroyers, as do SOTLs. The only thing I can think of is that they had a frigate and SOTL in the same area, and the frigate moved and the SOTL moved to the same tile that the frigate had been occupying.

 

[Jabba]

Yeah, it's from circumnavigation. Thanks.