Here's a wild theory-
When Keamey goes into the safe in the freighter to get the 2nd protocol folder containing information on where Ben is going and what he is doing, the captain of the boat asks him "How could Widmore possibly know that?" To which Keamey replies, "Because Charles Widmore is a very smart man."
And, in the lamppost station, Ms. Hawking tells us that a very smart man built the pendulum and designed the series of equations that approximates the location of the island.
Could Charles Widmore have built the pendulum, or, at the least, financed the construction of the pendulum giving him access to its information and approximations? That would more than justify his reasons for being able to locate the island and park his freighter 5 miles off its coastline in the first place. What do you all think?
It's a good idea, but if Widmore built it, I highly doubt he still has access to the data. If he did, it wouldn't have taken so long to find the island and he wouldn't have needed the anomaly.