This is a tutorial from Ducimus on postion reports and what you can do even if you think you are a million miles away from doing anything at all. This is the use of the map in the TMO mod created by Ducimus.
lets say the little X i drew is a contact report on a convoy that is moving at 9 kts and heading NE. So the first thing you do is pull down your chart to see how far he can travel at that speed, and how long it will take him. According to this handy dandy chart, a target moving at 9 kits can travel almost 72 NM in 8 hours. So i just used that since im a bit a ways from him.
Here i drew my circle, and faced it NE, same course as the convoy, and 72NM wide, centered on his current position. In 8 hours, assuming no radical changes in course, he should be somwhere where the line intercets the circumference of the circle. Not exact, but in that general vacinity. So now, i know where he will be, which is alot more important then where he currently is, if i plan to intercept him.
But how long will it take me to get there, and how fast would i have to go to be able to intercept him? Will i make it to that area in time? Is it possible to intercept him, or is this a fuel burning wild goose chase?
Time to go back to the chart:
Since im plotting on an 8 hour time frame, ill use the same for myself. Going at 19 kts, i can cover a distance 152NM. So lets plot that out.
So here's an 8 hour plot. Where i could be in 8 hours, and where he could be in 8 hours based on my projected speed of 19 kts, and his current speed of 9 kts. Now, really, i'll probably be pushing 20 to 21 kts, so i'll acutally cover this a bit faster.
In short, here is a contact report that i can get a firing position on, but barely. Now if this contacts speed was report at 12 kits, or somethign higher, this plot would have come out differently, and i'd probably have decided not to chase it and conserve my fuel. But in this case, it might be worth the fuel expenditure because we know we can overtake him if we want.