From the MarineTraffic point of view, ports are defined as bounding boxes usually covering the harbor and anchorage as well as the surrounding area. There are more than 7.000 ports and 10.000 marinas in our database while we are currently recording Port Calls for most major ports and a few marinas.
Port Calls reporting is based on processing of the AIS positions that are being received by MarineTraffic - it is not something broadcast by the vessels themselves. Thus, a Port Call is registered when we record two positions of a vessel inside and outside of the port's bounding box, within a short interval.
A Port Call might not get recorded because of any of the following reasons:
- no AIS coverage (both in the port and the surrounding area) or the subject vessel did not broadcast any AIS information (switched off transponder)
- the vessel left the port and then switched on her AIS transponder
- the subject port area is not registered in our database