AIS Targets Approaching Sabang

Non-eventful motoring passage so far with little wind. On our second night out, as we approach Sabang, we need to cross the shipping lanes as expected. Normally with such heavy traffic there are defined shipping lines much like a highway where ships always get in line and stay left like in Singapore Straits, English Channel, Straits of Hormuz or even further south in the Malacca Straits. Here there are no defined shipping lanes it is quite the free for all. Massive 366m supertankers traveling at 20 knots both ways between Middle East and China, Japan Korea etc. We have to cross the paths of these behemoths with only about 5knots of speed. It takes many miles for these ships to come to a stop and with all the other traffic their ability to turn and not hit another ship are pretty limited. So really it is up to us for self preservation to maneuver around and between these ships. Luckily the mandatory introduction of the Automatic Identification System (AIS) on board commercial ships over last decade or so makes this task at least somewhat manageable. The AIS system is installed aboard all commercial ships and it automatically transmits position, course, speed and other interesting tidbits about each vessel. We have AIS installed on Escapade to allow us to receive all this information as well as transmit our own information to other vessels in the area. Our plotting software then plots all these ships over our navigation charts and calculates each ships closest point of approach (CPA) and time to CPA (TCPA). Obviously a CPA distance less than the size of a ship like 0.25 miles is not good and indicates we are on a collision course. So the objective in crossing the shipping lanes is choose courses and speeds that get us across the shipping lanes as quickly as possible but to also maximize the CPA distance to each crossing ship. I took the above screenshot about halfway across the shipping lanes at about 10pm. At this point we had let Shagra (366m supertanker) and Genius Master (366m container ship) go past and were trying hard to pass in front of Hirada (another 366m supertanker). We had to do this for about 6 hours nonstop to get across. Challenging but fun.