I have done something, waiting for the patch (I hope there will be a fix for that!

)
I often see the same ships (petrolier Cimarron, Liberty ship...) so I have done on a paper a little drawing of each ship silhouette I have seen I have noticed the correct point to make my statement by comparing my stadimeter statements with the data I have found with the ruler on the map. Now I know where to move the stadimeter to have good results.
Waiting for better...