AIS identity mismatch is checked by asking other vessels or shore stations what they receive.
The simplest method to check own-ship transmitted identity, position, and movement information is to contact another vessel or shore station. This external corroboration helps confirm whether the displayed AIS data matches reality. Without this step, a single source cannot reliably verify the accuracy of its own broadcasted static identity fields.
Static identity fields include the MMSI, call sign, name, IMO number, vessel dimensions, and ship type. Several of these are set during installation and require amendment when vessel identity or configuration changes. Reviewing whether these configured fields need updating is a critical step in resolving discrepancies. If the internal data is outdated, it may cause apparent mismatches without any external interference.
Official guidance notes that invalid or duplicated MMSIs occur and can confuse target association. Reports from vessels using the same MMSI can appear as one target jumping between positions on a graphical display. Such mismatches have more than one data-quality explanation and do not establish deliberate spoofing. One must consider these technical errors without assuming intent.
