Type 0 Extension 11 - mattpascoe135/dab GitHub Wiki
#Extension 11 - Region definition The Region definition feature defines the geographical area by providing the cross reference between a Region Identifier and a TII list, and optionally geographical co-ordinates. The geographical area shall always be defined in terms of a TII list (GATy = "0000"), regardless of whatever other means of definition is also signalled (GATy ≠ "0000"). The feature is encoded in extension 11 of FIG type 0 (FIG 0/11). Figure 66 shows the structure of the Region definition field which is part of the Type 0 field (see also figure 4).
This feature shall use the SIV signalling (see clause 5.2.2.1). The database shall be divided by use of a database key. Changes to the database shall be signalled using the CEI.
The following definitions apply:
###GATy (Geographical Area Type): this 4-bit field shall indicate the coding method for the geographical area. The following values of the GATy field are defined (the remaining values are reserved for future use of the geographical area field). In all further cases, the length of the geographical area field shall be defined by a byte length indicator contained within the first byte of the field and encoded in the same way as in the case GATy = "0000"):
b15 - b12
0 0 0 0 : Geographical area defined by a TII list;
0 0 0 1 : Geographical area defined as a spherical rectangle by the geographical co-ordinates of one corner and its latitude and longitude extents.
###G/E (Global/Ensemble) flag: this 1-bit field shall determine the coverage area over which the RegionId is defined as follows:
0: Ensemble coverage area;
1: Global coverage area (area defined by CountryId + ECC).
###RegionId (Region identifier): this 11-bit field, organized as a 5-bit upper part and a 6-bit lower part, shall identify the region. The value RegionId = "000...0" is reserved (see clause 8.1.8).
###Geographical area: this field defines the area of the region in terms of a TII list or a rectangle based on co-ordinates.
##TII list: this field defines the geographical area in terms of the service area of all transmitters identified in the list:
###Rfu: this 3-bit field shall be reserved for future use of the associated geographical area field excluding the first byte. The Rfu bit shall be set to "0" for the currently specified definition of this associated field;
###Length of TII list: this 5-bit field, expressed as an unsigned binary number, shall represent the length in bytes (maximum 25) of the TII list field, excluding the byte in which this length parameter is carried.
The definitions below apply to one transmitter group sharing a main identifier:
###Rfa: this 1-bit field shall be reserved for future additions. The bit shall be set to "0" until it is defined;
###MainId (Main Identifier): this 7-bit field, expressed as an unsigned binary number, shall identify a group of transmitters (see clause 8.1.9);
###Rfa: this 3-bit field shall be reserved for future additions. The bits shall be set to zero until they are defined;
###Length of SubId list: this 5-bit field, expressed as an unsigned binary number, shall represent the length in bytes (maximum 23) of the SubId list field. The length "00000" shall be reserved for future use;
###SubId list: this list shall contain a number of SubIds. Padding bits (0 to 7) shall be added for byte alignment;
###SubId: this 5-bit field, expressed as an unsigned binary number, shall signal a Sub-identifier associated with a transmitter (see clause 8.1.9);
###Padding: this field shall contain sufficient bits in the range 0 to 7 to make up the overall length of each SubId list field to an integral number of bytes. Padding bits shall be set to "0".
##Co-ordinates: this field defines the geographical area in terms of a rectangle based on co-ordinates.
###Latitude coarse: this 16-bit field, coded as a two's complement number, shall specify the coarse latitude of a corner of the spherical rectangle that defines the area. It shall be calculated by multiplying the value of the Latitude coarse field by (90° / 215). Southern latitudes shall be considered negative and northern latitudes positive;
###Longitude coarse: this 16-bit field, coded as a two's complement number, shall specify the coarse longitude of a corner of the spherical rectangle that defines the area. It shall be calculated by multiplying the value of the Longitude coarse field by (180° / 215). West of Greenwich shall be considered negative and east of Greenwich positive;
###Extent of Latitude: this 12-bit field, coded as a unsigned binary number, shall specify the extent of latitude of the spherical rectangle that defines the area. It shall be calculated by multiplying the value of the extent of Latitude field by (90° / 215);
###Extent of Longitude: this 12-bit field, coded as a unsigned binary number, shall specify the extent of longitude of the spherical rectangle that defines the area. It shall be calculated by multiplying the value of the extent of Longitude field by (180° / 215).
The database key comprises the OE and P/D flags (see clause 5.2.2.1) and the RegionId field.
The Change Event Indication (CEI) is signalled by the Length of TII list field = 0.