Why a ship can have a position but no name
An AIS marker is a received message, not a complete registry record. Position reports and descriptive information do not necessarily arrive together. A tracker can therefore know where a transmitter was observed while its vessel name is still unavailable. The US Coast Guard AIS FAQ distinguishes position information from static and voyage information. Do not interpret a blank name as proof that a vessel is suspicious, unregistered or deliberately hiding. The missing value may simply be absent from the information available to this website.
MMSI and IMO answer different questions
MMSI identifies the maritime radio identity used in AIS messages. An IMO ship number serves a different purpose: the IMO identification scheme assigns a persistent identity to a ship, retained through changes such as its name, owner or flag. The fields are not interchangeable. When following a renamed ship across records, an available IMO number is useful corroboration. A name alone is a poor matching key: spelling, abbreviations and name changes can make two records look different, or make unrelated records look alike.
What the Coast Guard's VIVS tool checks
The Vessel Information Verification Service compares received AIS static information with relevant US licensing and vessel documentation records. Its scope is the Nationwide AIS coverage area, not every vessel worldwide. NAVCEN explicitly says it is not a real-time service and updates can take two business days. That makes it a useful separate identity check, not a replacement for a recent position report. A mismatch is a reason to examine the fields and their dates; it is not an automatic finding about a vessel's conduct.
A practical way to compare two vessel cards
Start with the observation timestamp, then compare identifiers, coordinates and descriptive fields separately. Record which provider supplied each observation. If one card has a newer position but an older name, keep those two statements separate instead of choosing one whole card as universally correct. A destination text field does not establish that a port has confirmed an arrival. Likewise, an unavailable speed is not the same observation as a measured speed of zero. These distinctions make a useful research note much clearer than a screenshot with no time or source.
Use PocketWorld as a geographic starting point
Open the ship explorer and select a reported vessel to inspect the available identity, source and time. Coverage and completeness depend on the configured providers; we do not claim access to VIVS records for every marker. This guide links you to the official verification service rather than silently filling gaps with guessed names. If a field is unknown, leave it unknown in your comparison. For operational navigation, vessel identification or a safety decision, use the appropriate official services and equipment, not this educational map.
Data sources
Official references are linked beside the explanations above. This educational guide does not report current marine conditions or provide navigation advice.