LGN1's SH3 Log mod forces one to make an estimation of the GRT of the ships one has sunk. With all the ships one can mod into SH3 nowadays, it sometimes happens, that one sinks a ship one does not recognize. In these cases I guess most of us just make a crude guess about the GRT.
The US Coast Guard has a formula for GRT calculations. Here's the formula changed into the metric system:
Download from here:
http://www.mediafire.com/download/oj...31j517/grt.tga
I haven't had time to try this in the game yet, so I'm not 100% sure I made the feet to meters conversion right, so maybe doublecheck the results with the recognition manual when possible.