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Missing a pertinent NOTAM can cause a significant safety hazard and missing a Digital NOTAM is no different. To prevent such risks, the text NOTAM production and distribution systems have mechanisms (sequential numbering, checklists, etc.) that enable a user to check if they are in possession of all applicable NOTAM messages. Similar mechanisms must be put in place when working with Digital NOTAMs. However, these mechanisms are allowed to be different from the mechanisms used for the synchronisation of NOTAM text message sets. The requirements may also be different, as Digital NOTAM synchronisation requires both:

  • the synchronisation of the BASELINE data, without which the TEMPDELTA TimeSlices cannot be processed correctly;
  • the synchronisation of the PERMDELTA and TEMPDELTA data itself;

This could be supported through reports that contain the list of all valid TimeSlices - sequence number and correction number for each feature, identified by UUID or by a SNAPSHOT TimeSlice containing feature identifying properties (natural key). An AIXM BasicMessage could be used for this purpose.

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Another aspect that requires the attention of Digital NOTAM receivers is the risk of duplicate information, in particular for data situated in the vicinity of two or more areas of responsibility. This duplication already exists today in the form of different NOTAM messages issued by different States for the same facility or situation. With Digital NOTAMs, this risk to happen as well because of potential difficulties in coordinating the data publication between neighbouring States, also taking into consideration the need for rapid data dissemination. With Digital NOTAMs, the risk should be reduced at least when it concerns updates to existing facilities, as the TEMPDELTA is expected to be issued by the same authority who has issued the BASELINE data. However, for situations when a new temporary item is announced (such as a temporary obstacle in the vicinity of the boundary), there is still a risk of lack of coordination. This may result in duplicate data being issued. Therefore, Digital NOTAM recipients should foresee appropriate actions for dealing with both potentially duplicate PERMDELTA and BASELINE data.

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