Modern radars have a wonderful ability to project the closest point of approach (CPA) between you and another vessel, and when (TCPA) this will occur. To do this the radar needs to know your speed and heading, and that of the target. Some times there is poor data in the loop in which case the CPA calcs are going to be off. In the photo above the radar is projecting the true course of the ship with the CPA information in the data box beside.

The CPA is projected at .443 nautical miles and the TCPA is seven minutes and 14 seconds.

Here is the actual crossing, which we are happy to report took place as projected. Every few months we like to compare the CPA data that occurs with the calcs, to make sure the radar is doing its job correctly. So far, as long as we and the other vessel maintain course and speed, the data has been spot on.