The following example shows the BGL file format of a database header.
;DATABASE HEADER ********************************************************
dw0001;00 world set number (not saved to file list)
dd0004c4eabh;02 N bound 43 degrees Meter units
dd000400000h;06 S bound
dd0cf000000h;10 E bound 85 degrees 32-bit pseudo
dd0bf000000h;14 W bound
ddVOR_DATA;18 VOR_DATA
dw50;22 lowest vor freq (channel 0–199)
dw50;24 highest vor freq (108.00–117.95)
ddSYNTH_SEEDS_08;26 seeds level 8
ddSYNTH_SEEDS_09;30 seeds level 9
ddSYNTH_SEEDS_10;34 seeds level 10
ddSYNTH_SEEDS_11;38 seeds level 11
ddSYNTH_SEEDS_12;42 seeds level 12
ddSYNTH_SEEDS_13;46 seeds level 13
ddSYNTH_SEEDS_14;50 seeds level 14
ddSYNTH_SEEDS_15;54 seeds level 15
ddOBJECT_DATA;58 OBJECT_DATA
ddLIBRARY_DATA;62 LIBRARY_DATA
ddFACILITIES_DATA;66 FACILITIES_DATA
ddANCHOR_POINTS;70 ANCHOR POINT DATA
ddCOM_DATA;74 COM RADIO DATA
ddADF_DATA;78 ADF DATA
ddDYN_PATH_DATA;82 DYNAMIC OBJECT PATHS
dw3,3,2,1;86 Library id min
dw5,3,2,1;94 Library id max
ddMISC_DATA;102 MISC_DATA (iom, landme)
ddTITLE_DATA;106 TITLE AND DESCRIPTION DATA
ddMAGDEC_MAP;110 MAGVAR MAP PTR
ddEXCEPTIONS_DATA;114 EXCEPTION LIST PTR
dd0;118 spare 1
dd0;122 (not saved to file list)
dw0;126 (not saved to file list)
Important: If there is no data for any given pointer, set its value to 0.
The following table describes the components and characteristics of the BGL extended header record.
Note: If the BGL system finds the “magic number” in the offset 118 spare slot, the extended header information is used for facility and version information. This feature was added for Flight Simulator 98; earlier versions of Flight Simulator use only the basic header shown in the preceding example. Flight Simulator 98 is backward compatible with the basic header.
| Name | Offset, size | Description |
| World set # | 0, UINT16 | |
| North lat bound | 2, SINT32 | |
| South lat bound | 6, SINT32 | |
| East lon bound | 10, ANGL32 | |
| West lon bound | 14, ANGL32 | |
| VOR data | 18, PTR32 | |
| Lowest VOR channel | 22, UINT16 | |
| Highest VOR channel | 24, UINT16 | |
| Seed level 8 data | 26, PTR32 | |
| Seed level 9 data | 30, PTR32 | |
| Seed level 10 data | 34, PTR32 | |
| Seed level 11 data | 38, PTR32 | |
| Seed level 12 data | 42, PTR32 | |
| Seed level 13 data | 46, PTR32 | |
| Seed level 14 data | 50, PTR32 | |
| Seed level 15 data | 54, PTR32 | |
| Object data | 58, PTR32 | |
| Library data | 62, PTR32 | |
| Facility data | 66, PTR32 | |
| Anchor data | 70, PTR32 | |
| COM radio data | 74, PTR32 | |
| ADF radio data | 78, PTR32 | |
| Dynamic scenery data | 82, PTR32 | |
| Library minimum | 86, UINT64 | |
| Library maximum | 94, UINT64 | |
| Miscellaneous data | 102, PTR32 | |
| Title data | 106, PTR32 | |
| Magvar data | 110, PTR32 | |
| Exception (inclusion) filter data | 114, PTR32 | |
| Magic # | 118, UINT32 | =0x87654321 |
| Reserved | 122, PTR32 | =0x00000000 |
| Reserved | 126, UINT16 | =0x0000 |
| File GUID | 128, GUID128 | Use Visual C++ GUIDGEN utility to generate this value. |
| Version | 144, UINT32 | =0x00000001 |
| Data pointers count | 148, UINT32 | =N |
| Data pointer list | *, PTR32*N | |
| Facility2 name list | 152, PTR32 | See NAME_LIST |
| Reserved | 156, PTR32 | |
| Facility2 data | 160, PTR32 | See OBJECT_CONTAINER |
Important: The File GUID entry must be unique for each and every version of the file. This value is used to detect when the index file, which is derived from the new facility data, needs to be rebuilt. Failure to rebuild the index file can result in incorrect or outdated facility information being presented to the user.
The following table describes the primitive data types used in the database header.
| Data type | Description |
| UINT8 | 8-bit general-purpose data type. |
| UINT16 | 16-bit general-purpose data type. |
| UINT32 | 32-bit general-purpose data type. |
| UINT64 | 64-bit general-purpose data type. |
| PTR32 | Pointer data type. |
| ENUM32 | 32-bit enumerated value. This data type is restricted to a very specific set of values. |
| GUID128 | 128-bit globally unique ID. Think of this data type as a computer-generated name or label. Generally, the GUIDGEN utility is used to generate this data type. |
| FREQ32 | 8-digit BCD number. The units of the number is 100 Hz. For example, a frequency of 122.250 MHz would have a value of 0x01222500; a frequency of 699.2 kHz would have a value of 0x00006992. |
| RWY32 | 32-bit number that designates the runway number or orientation, as follows: 1–36, runway numbers 37, N/S 38, E/W 39, NW/SE 40, SW/NE |
| STRINGZ4 | Variable-length string, but with an additional requirement that the length be a multiple of 4 bytes. There should be 1-4 bytes of 0 (zero) that terminates the string, the number of 0 bytes being whatever number is required to make the total length of the string divisible by 4. If the string length is already divisible by 4 (prior to adding any 0 bytes), you must add 4 bytes of 0 to the string; that is, the string must always be followed by at least one byte of zero. |
The records in the following table show the general structure of different classes of records. These records aren't meant to be used in a database, but are documented to show the common fields of each record class.
| Name | Size | Description |
| IF48 (ANGL48) | ||
| Reserved | UINT16 | =0x0000. |
| Lo | UINT16 | Lower 16 bits of value (fraction). |
| Hi | SINT32 | Upper 32 bits of value (integer). |
| OBJECT_ | ||
| Type | ENUM32 | See OBJECT_ enum list. |
| Size | UINT32 | Size of remainder of object. |
| Data | UINT8*Size | Contents is object-specific. |
| LOCATION_ | ||
| Type | ENUM32 | =LOCATION_ |
| Size | UINT32 | Size of remainder of object. |
| Latitude | IF48 | Meters from equator. |
| Longitude | ANGL48 | |
| Elevation | IF48 | Meters (MSL). |
| Heading | ANGL32 | Pseudodegrees. |
| <other data> | (unknown) | The format of the rest of the record depends on the particular type of record. |
| OBJECT_NULL | Commonly used to mark or terminate a sequential list of other types of records. | |
| Type | ENUM32 | =OBJECT_NULL |
| Size | UINT32 | =0x00000000 |
| OBJECT_CONTAINER | Used to group a collection of related records. For example, a collection of records that make up an airport description are placed within an OBJECT_CONTAINER record. | |
| Type | ENUM32 | =OBJECT_CONTAINER |
| Size | UINT32 | Size of remainder of object. |
| Container type | ENUM32 | CONTAINER_AIRPORT CONTAINER_VOR CONTAINER_NDB |
| Reserved | UINT32 | =0x00000000 |
| Data | OBJECT[N] | Other objects in this container. |
| LOCATION_AIRPORT | Included in the airport container object and gives the ARP lat/long as well as the field elevation data. There should be exactly one LOCATION_AIRPORT record in an airport container. | |
| Type | ENUM32 | =LOCATION_AIRPORT |
| Size | UINT32 | Size of remainder of object. |
| ARP Latitude | IF48 | Meters from equator. |
| ARP Longitude | ANGL48 | |
| Field elevation | IF48 | Meters (MSL). |
| Heading | ANGL32 | <unused> |
| LOCATION_RUNWAY | Include one LOCATION_RUNWAY record for every runway (and helipad) that an airport has. Any LOCATION_NAVAIDS that follow a LOCATION_RUNWAY within an AIRPORT_CONTAINER are assumed to be related to the LOCATION_RUNWAY until a new LOCATION_RUNWAY is found. This ordering inside the AIRPORT_CONTAINER creates the relationship between localizers and ILSs and the associated runway. | |
| Type | ENUM32 | =LOCATION_RUNWAY |
| Size | UINT32 | Size of remainder of object. |
| Center latitude | IF48 | Meters from equator. |
| Center longitude | ANGL48 | |
| Center elevation | IF48 | Meters (MSL). |
| True heading | ANGL32 | Pseudodegrees. |
| Magnetic variation | ANGL32 | Pseudodegrees. |
| Length | UINT32 | Feet. |
| Width | UINT32 | Feet. |
| Runway type | ENUM32 | RUNWAY RUNWAY_LEFT RUNWAY_RIGHT RUNWAY_CENTER HELIPAD |
| Runway number | RWY32 | Orientation. |
| Surface material | ENUM32 | SURFACE_UNKNOWN SURFACE_DIRT SURFACE_CEMENT SURFACE_ASPHALT SURFACE_GRASS SURFACE_GRAVEL SURFACE_OIL_TREATED SURFACE_MATS SURFACE_SNOW SURFACE_CORAL SURFACE_WATER |
| Reserved | UINT32 | =0x00000000 |
| LOCATION_SET | Used to identify specific locations in an airport where the user might wish to place their aircraft. Currently, only takeoff locations can be identified, but in the future, this record will be used to mark parking apron tiedown locations, gate locations, and so on. | |
| Type | ENUM32 | =LOCATION_SET |
| Size | UINT32 | Size of remainder of object. |
| Latitude | IF48 | Meters from equator. |
| Longitude | ANGL48 | |
| Elevation | IF48 | Meters (MSL) |
| Heading | ANGL32 | Pseudodegrees |
| Set type | ENUM32 | SET_TAKEOFF |
| Subtype | ENUM32 | (Set type=SET_TAKEOFF) RUNWAY RUNWAY_LEFT RUNWAY_RIGHT RUNWAY_CENTER HELIPAD |
| Number | RWY32 | Set type=SET_TAKEOFF) orientation |
| Reserved | UINT32 | =0x00000000 |
| LOCATION_TOWER | Identifies the location of the airport's tower and the MSL altitude of the tower viewpoint. Typically, only one of these records exists in an airport container record, but in some cases, more that one is be specified. | |
| Type | ENUM32 | =LOCATION_TOWER |
| Size | UINT32 | Size of remainder of object. |
| Latitude | IF48 | Meters from equator. |
| Longitude | ANGL48 | |
| Altitude | IF48 | Meters (MSL) |
| Heading | ANGL32 | <unused> |
| FREQUENCY | Used to identify the various communication frequencies that the airport uses. | |
| Type | ENUM32 | =FREQUENCY |
| Size | UINT32 | Size of remainder of object. |
| Frequency | FREQ32 | |
| Type | ENUM32 | FREQ_ATIS FREQ_MULTICOM FREQ_UNICOM FREQ_CTAF FREQ_GNDCON FREQ_CT FREQ_CDEL FREQ_APCON FREQ_DEPCON FREQ_CENTER FREQ_FSS FREQ_AWOS |
| ICAO_ID | Used to identify the ICAO ID that is associated with the airport. | |
| Type | ENUM32 | =ICAO_ID |
| Size | UINT32 | Size of remainder of object. |
| Id | STRINGZ4 | |
| LOCATION_NAVAID | Included in a container record. Specific types of navaids are included in specific types of container records. For example, NAVAID_VOR and NAVAID_DME types should only be used in VOR containers and the NAVAID_NDB type should be used in an NDB container. Include the NAVAID_LOCALIZER, NAVAID_GLIDESLOPE, NAVAID_SDF, and NAVAID_MARKER types in airport containers. The frequency field of a navaid of type NAVAID_TACAN is assumed to be a BCD encoding of the‘channel’. Each NAVAID_TACAN record must have an associated NAVAID_DME that specifies the VOR frequency to tune so the DME capabilities can be used in a civilian aircraft. | |
| Type | ENUM32 | =LOCATION_NAVAID |
| Size | UINT32 | Size of remainder of object. |
| Latitude | IF48 | Meters from equator. |
| Longitude | ANGL48 | |
| Elevation | IF48 | Meters (MSL). |
| Heading | ANGL32 | Depending on navaid type this may be unused. |
| Frequency | FREQ32 | In the case of DME and GLIDESLOPE navaids, the value of the frequency must be the same as the VOR or LOCALIZER with which it's associated. |
| Type | ENUM32 | NAVAID_VOR NAVAID_DME NAVAID_NDB NAVAID_LOCALIZER NAVAID_GLIDESLOPE NAVAID_SDF NAVAID_MARKER NAVAID_TACAN |
| Class | ENUM32 | SSV_TERMINAL SSV_LOW_ALTITUDE SSV_HIGH_ALTITUDE NDB_COMPASS_LOCATOR NDB_MH NDB_H NDB_HH MARKER_OM MARKER_IM MARKER_BC |
| Flags | FLAG32 | VOICE_ANNOUNCE |
| Reserved | UINT32 | =0x00000000 |
| Identifier | STRINGZ4 | |
| NAME_LIST | Order name entries in a hierarchical fashion. Start with a FACILITY_REGION entry and follow it with all the FACILITY_COUNTRY entries that are in that region. Follow each FACILITY_COUNTRY entry with all the FACILITY_STATE entries that are part of that country, and then follow each FACILITY_STATE entry with all the FACILITY_CITY entries that are within that state's boundaries. FACILITY_AIRPORT and FACILITY_ICAO_ID entries are ordered in the list after each FACILITY_CITY entry that they are associated with. The FACILITY_AIRPORT entry precedes the related FACILITY_ICAO_ID entry. (The FACILITY_ICAO_ID name always includes the country code; for example, O'Hare is designated KORD, not ORD). | |
| Type | ENUM32 | =NAME_LIST |
| Size | UINT32 | Size of remainder object. |
| Language ID | UINT32 | =0x00000409 for U.S. English. (See winnt.h for other ID values; search for"LANG_".) |
| String type | ENUM32 | =STRINGZ_ASCII |
| Reserved | UINT32 | =0x00000000 |
| Name entry count | UINT32 | Number of name entries. |
| Name entries | NAME_ENTRY [N] | |
| Note: You must include more than one NAME_LIST record in a BGL file; at minimum, there must be two. The NAME_LIST records are sequential in the file. The last NAME_LIST record must be an OBJECT_NULL record. If there are more than two NAME_LIST records in the file, it is assumed that each NAME_LIST record has a different language ID value; this way, you can use a single BGL facility file to support multiple languages. | ||
| NAME_ENTRY | See preceding description. | |
| Type | ENUM32 | =NAME_ENTRY |
| Size | UINT32 | Size of remainder of object. |
| Facility type | ENUM32 | FACILITY_REGION FACILITY_COUNTRY FACILITY_STATE FACILITY_CITY FACILITY_AIRPORT FACILITY_VOR FACILITY_NDB |
| Object pointer | PTR32 | See OBJECT_CONTAINER. |
| Name | STRINGZ4 | |