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In addition, developers of Digital NOTAM encoding application shall be aware that in particular situations the operator might need to adjust the content of the Q line (code, purpose, area of influence, etc.) in order to ensure a certain processing for that NOTAM for pre-flight purpose. Therefore, it might be necessary to allow modifications in the items A and Q of an automatically generated text NOTAM. Manual intervention in the other NOTAM items is strongly discouraged.

Use of upper and lower case text

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The Event schema allows the automatic generated NOTAM text to be coded and provided as part of the Digital NOTAM data set. As for its distribution it is possible to use more advanced channels than AFTN, there is no constraint for this text to be only in upper case. As demonstrated by several human factors studies, the use of the usual "sentence case" mix of lower and upper case improves the readability of the information. This is particularly important for Pre-flight Information Bulletin (PIB) applications. Therefore, the Digital NOTAM Specification provides rules for generating the NOTAM text using lower case in general, while upper case is used only in specific cases, such as start of a sentence, place names, certain abbreviations and acronyms, etc.For NOTAM transmission over AFTN, the conversion into full upper case will still have to be done, but it is straight-forward.

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One of the major advantages of Digital NOTAM (as compared with the current text NOTAM) is that it enables the automatic creation of more precise graphical representations of the event. In the case of an ad-hoc restricted area, a navigation warning, a temporary obstacle, a taxiway closure, etc. the real location and geometry of the feature shall can be presented graphically (right side of the following image) and not the radius of influence (left side of the following image, as provided by the coordinates/radius block in item Q of an ICAO NOTAM).               

The Q line of an ICAO NOTAM message includes a geographical position and a radius, which were originally intended as NOTAM filtering parameters, for selecting NOTAM geographically. This is commonly exploited in order to represent the NOTAM graphically, as a circle. For airport NOTAM, the circle is typically centered on the Airport Reference Point (ARP) location and has a radius of 5 NM. Also, many NOTAM are issued with a maximum radius of 999 NM in order to ensure that they appear in all PIB. These aspects limit significantly the use of this location/radius as graphical representation of a NOTAM.

A Digital NOTAM can be represented graphically much more precisely, showing the extent of the area or the feature affected. This is exemplified in the following two pictures, which compare the display of a restricted area as a circle (based on the NOTAM Q line) versus the real geometry of the airspace (as made possible by Digital NOTAM).

                  Text NOTAM  (centrecenter/radius)                              Digital NOTAM (real geometry)

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Graphical visualisation of Digital NOTAM usually requires data which goes beyond strictly the features affected by the event. For example, a taxiway closure Digital NOTAM will provide the information about the closure status, eventual exceptions and schedules of the closure. In order to graphically display this closure on an airport map, the geometry of that taxiway is necessary. This might not be available in the message that contains the Event data and might require querying a source of reference database. A system providing Digital NOTAM data to consumer application might include the provision of ‘reference data’, to support applications such as graphical visualisation. Such data might be included directly in the Digital NOTAM messages (as an option) or be provided as a separate service.

The graphical capabilities offered by Digital NOTAM can be exploited in the provision of digitally enhanced Preflight Information Bulletin services and products. Such a specification was developed through the SESAR Research projects.

Event filtering capabilities

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