MAPS.BSA is a Name Record (0x0100) BSA file containing the overland data for 62 regions of the game. The file contains 4 different record types. Each described region has one of each record type associated with it, for a total of 248 distinct records within the file. Within each of the region's associated records, all navigable settlements, dungeons, shrines, etc are listed and described.
General File LayoutEdit
Each described region has 4 records associated with it. Records are all named in 7-bit ASCII string DOS8.3 format. The 3 character record extension is the ASCII representation of the region's decimal number, with leading 0's. Ex: Daggerfall (0x11) is identified by records ending with "017", such as "MAPPITEM.017". The leading 8 characters indicate the specific type of record:
- These records simply lists the names of all navigable locations within the region, stored as an array of 7-bit ASCII strings.
- These records describe the coarse GPS data, and type of the navigable locations within the region.
- These records describe the exterior of each navigable location within the region.
- These records describe the dungeon interiors of each navigable location within the region.
Ex: "MAPNAMES.005" is the list of the names of all navigable places within Dwynnen.
Location Name Record (MapNames)Edit
This type of record contains the count of all navigable locations within the record's associated region, immediately followed by the names of all navigable locations within the record's associated region.
The first four bytes are the count of name elements as an UInt32, referred to as LocationCount. This record is variably sized, but must always be 4 + ( 32 * LocationCount ) bytes long.
Immediately following this count are the actual names of all the navigable locations for the record's associated region, each 32 characters wide, stored as a null-terminated, 7-bit ASCII string. There are exactly LocationCount elements.
Location GPS Record (MapTable)Edit
These records report the GPS location data, as well as the type of the described location, for each navigable location within the record's associated region. Each record consists of a contiguous list of MapTable structures. Each MapTable structure is 17 bytes long in size.
There are exactly MapNames.LocationCount elements in the contained list, and each indexed record is the same location as in the map names.
|0-3||Int32||MapId||This numeric ID is used to associate values MapTable elements with LocationRecordElement elements. Each LocationExterior value must be described by a MapTable value. The first 20 bits of this field matches the first 20 bits of a LocationExterior.ExteriorData.MapId value; Simply match
|5-8||UInt32||LongitudeType||This field is actually the combination of the location's Longitude and type. Decoding instructions are below.|
|9-10||UInt16||Latitude||The location's latitude.|
Location Item RecordsEdit
The remaining two types of records (MapPItem and MapDItem) each use a common base format for their root data, described here. Each record consists of a contiguous list of the data for all the navigable locations for that record's associated region. Since not all locations have dungeons, Location Exterior Data Records may contain more elements than Dungeon Interior Data Records.
The base format, LocationRecordElement, is variably-sized. It consists of a DoorHeader, immediately followed by a contiguous list of zero or more Door elements, immediately followed by a LocationRecordElementHeader.
|0-3||UInt32||DoorCount||The count of Door elements which immediately follow this header as a contiguous list.|
Immediately following the DoorHeader is a contiguous list of Door elements, DoorCount in count, each 6 bytes long.
|0-1||UInt16||BuildingDataIndex||This is a valid index to an element within the LocationExterior.BuildingData array, or 0xffff which indicates this Door is not associated with an element of the BuildingData array. This places a maximum count of BuildingData elements at 0x7fff.|
|2||UInt8||NullValue||This value is always 0x00.|
|3||UInt8||Mask||This value is a mask of some type. The specific purpose is presently unknown.|
The LocationRecordElementHeader immediately follows the contiguous list of Door elements. Each LocationRecordElementHeader structure is 112 bytes long.
|0-3||UInt32||AlwaysOne1||This value is always 0x00000001 for all records.|
|4-5||UInt16||NullValue1||This value is always 0x0000 for all records.|
|6||UInt8||NullValue2||This value is always 0x00 for all records.|
|7-10||Int32||Y||This is the Y coordinate for the location in game world units. It's 256 times the longitude plus 0-255.|
|11-14||UInt32||NullValue3||This value is always 0x00000000 for all records.|
|15-18||Int32||X||This is the X coordinate for the location in game world units. It's 256 times the latitude plus 0-255.|
|19-20||UInt16||IsExterior||This value is an enumeration. Since there are only two valid values (described below), this may be treated as a Bool16.|
|21-22||UInt16||NullValue4||This value is always 0x0000 for all records.|
|31-32||UInt16||AlwaysOne2||Always 0x0001 for all records.|
|33-34||UInt16||LocationId||This is the unique LocationId for the location. This LocationId is used by the Quest Subsystem.|
|35-38||UInt32||NullValue4||Always 0x00000000 for all records.|
|39-40||Bool16||IsInterior||Exterior data (MapPItem) elements are FALSE (0x0000). Interior data (MapDItem) records are TRUE (stored as 0x0001).|
|41-44||UInt32||ExteriorLocationId||If the LocationRecordElementHeader describes interior data (MapDItem) and IsInterior is TRUE, this is the LocationRecordElementHeader for the exterior data (MapPItem) associated with this record. Otherwise, this value should be 0x0000. Since each DungeonInterior element must correspond to a LocationExterior element, this field's value must match a LocationExterior.LocationRecordElement.LocationId value.|
|45-70||UInt8[ 26 ]||NullValue5||Each element of this 28 byte field should be 0x00.|
|71-102||7-bit ASCII string||LocationName||Reports the NULL-terminated name of the location, but may not always exactly match the values in the MapNames record for the region. This value is used when displaying the name of a location when entering it. The fast travel map uses the MapNames record for display.|
|103-111||UInt8[ 9 ]||Unknown3||An unknown array of bytes, 9 bytes long.|
|0x0000||The LocationRecordElementHeader describes dungeon interior data.|
|0x8000||The LocationRecordElementHeader describes location exterior data.|
After the LocationRecordElementHeader, data specific to the record type (MapPItem or MapDItem) follows.
Location Exterior Data Record (MapPItem)Edit
Each MapPItem record begins with a list of UInt32 values with MapNames.LocationCount elements. This is a list of offsets to the LocationExterior structures for each location. These values are relative to the end of the list, so adding (LocationCount * 4) to the offset locates the actual record. One offset may be greater than a subsequent one; no data order is presumed.
At each offset indicated, a LocationExterior structure is present, which includes all fields from the LocationRecordElement and some data of its own.
|0-1||UInt16||BuildingCount||This is the count of BuildingData structures which immediately follow this header, as a contiguous list. This field must be less-than-or-equal-to 0x7fff.|
|2-6||UInt8[ 5 ]||Unknown1||Unknown Purpose.|
Immediately following the above header, is a contiguous list of BuildingData structures. Each BuildingData is 26 bytes long. BuildingData structures are associated with buildings within a settlement, such as a tavern.
|0-1||UInt16||NameSeed||This field is used as a seed value for generating the building's name.|
|2-9||UInt64||NullValue1||Should always be 0x0000000000000000.|
|10-17||UInt64||NullValue2||Should always be 0x0000000000000000.|
|18-19||UInt16||FactionId||This is the FactionId which should be associated with this building, or 0x0000 if no faction should be associated with this building. Valid values for this field are defined by the FACTION.TXT file.|
|20-21||Int16||Sector||This value seems to generally increase with each building. Changing this number at all crashes the game when the location is loaded. Always non-zero and ranges from 4 to 2329.|
|22-23||UInt16||LocationId||The value for this field should always be the same as the LocationRecordElementHeader.LocationId field.|
|24||UInt8||BuildingType||This indicates the type of the building. Valid values are defined in the Building Type Code enumeration.|
|25||UInt8||Quality||This specifies the quality of the building, always non-zero and ranges from 1 to 0x14 (20). Divide by 4 to rate on the "rusty-relics…" through "incense burning…" scale.|
|0-31||7-bit ASCII string||Name||Appears to be another name for the location, but changing the value has no visible effect on the game.|
|32-35||Int32||MapId||Since each LocationExterior value must be described by a MapTable value, this field must correspond to a MapTable.LocationId value. The first 20 bits of this field matches the first 20 bits of a MapTable.MapId value; Simply match ( LocationExterior.ExteriorData.MapId & 0x000fffff ) with ( MapTable.MapId & 0x000fffff ).|
|40||UInt8||Width||The width of the exterior data. This value may not be 0, and must be less-than-or-equal-to 8.|
|41||UInt8||Height||The height of the exterior data. This value may not be 0, and must be less-than-or-equal-to 8.|
|42-48||UInt8[ 7 ]||Unknown2||Unknown Purpose.|
|49-112||UInt8[ 64 ]||BlockIndex||Only the first Width * Height elements will have any meaning. See decoding instructions below.|
|113-176||UInt8[ 64 ]||BlockNumber||Only the first Width * Height elements will have any meaning. See decoding instructions below.|
|177-240||UInt8[ 64 ]||BlockCharacter||Only the first Width * Height elements will have any meaning. See decoding instructions below.|
|241-274||UInt8[ 34 ]||Unknown3||Unknown Purpose.|
|284-371||UInt32[ 22 ]||Unknown4||Unknown Purpose.|
|372-411||UInt8[ 40 ]||NullValue3||Each element is always 0x00.|
Interpreting the Block Data arraysEdit
The BlockIndex, BlockNumber, and BlockCharacter arrays all have a fixed size of 64 elements, but only the first Width * Height elements are used; the remainder are ignored. All 64 elements must be read just the same. These values are used to load the appropriate records from the BLOCKS.BSA file, which contains the automap data and are in turn used to load the appropriate meshes and models from ARCH3D.BSA to actually display the scene.
When accessing the block arrays, they should be synchronized. This is to say BlockIndex[ 5 ] should refer to the same Block record as BlockCharacter[ 5 ] and BlockNumber[ 5 ]. If one adds, removes, or reorders any array then one must reorder both of the other arrays to keep them synchronized.
The arrays are stored in west-to-east, south-to-north order. This means index 0 refers to the southwest corner of the location, and index ( Width * Height ) refers to the northeast corner of the location. Locations are not required to be squares (Width is not required to equal Height).
The details of the logic are described in Block Record Indexes.
Dungeon Interior Data Record (MapDItem)Edit
Each MapDItem record begins with an UInt32 count (DungeonCount) of DungeonInterior elements contained within the record.
Dungeon Offset SectionEdit
Immediately following the DungeonCount field is a contiguous list of DungeonOffset values. Each value is 8 bytes long. The elements are not required to be in any particular order; That is to say the first element's offset could be higher than the second element's offset.
|0-3||UInt32||Offset||These offsets refer to the DungeonInterior elements of the record, and all offsets are relative to the end of the offset list.|
|4-5||Bool16||IsDungeon||This value is TRUE (stored as 0x0001) for all elements.|
|6-7||UInt16||ExteriorLocationId||Since each DungeonInterior element must correspond to a LocationExterior element, this field's value must match a LocationExterior.LocationRecordElement.LocationId value.|
Dungeon Record DataEdit
Each DungeonOffset.Offset refers to a DungeonInterior element. This is also a composite structure, similar to the LocationExterior structure.
Immediately following the LocationRecordElement structure is a DungeonHeader structure.
|10-11||UInt16||BlockCount||This is the count of the DungeonBlock elements in the contiguous list which follows. This value must be greater than 0 and less-than-or-equal-to 32.|
|12-16||UInt8[ 5 ]||Unknown3||Unknown Purpose.|
Immediately following the DungeonHeader is a contiguous list of DungeonBlock structures, each 4 bytes long. There are BlockCount elements in this list.
Each DungeonInterior structure contains a contiguous list of DungeonBlock structures. There are exactly DungeonHeader.BlockCount elements in this list.
|0||UInt8||X||The X coordinate of the block.|
|1||UInt8||Z||The Z coordinate of the block.|
|2-3||UInt16||BlockNumberStartIndex||This is a concatenation of the BlockIndex and BlockNumber values. Decoding instructions follow.|
The X and Z fields indicate how the blocks should be arranged in a two-dimensional grid. Dungeons are not required to be uniform such as squares or rectangles. They can contain empty spaces, or have spurs.
Ex: Privateer's Hold B0000012 B0000009 @S0000999 B0000003 B0000006
Ex: Mantellan Crux S0000005 S0000006 S0000004 S0000003 S0000002 S0000001 @S0000000
|0-9||UInt16||BlockNumber||This value is used for decoding the string name of the RDB record from BLOCKS.BSA. As of the current patch, bits 8-9 are only necessary for Privateer's Hold (999); all other blocks require only bits 0-7.|
|10||Bool||IsStartingBlock||This bit is set (1) if this block is the "entrance" block. This is the block where the player starts when entering a dungeon. This bit is reset (0) otherwise. All DungeonInterior records must have one and only one DungeonBlock element with this bit set (1).|
|11-15||UInt8||BlockIndex||This value is used for decoding the string name of the RDB record from BLOCKS.BSA. Valid values are described in Block Record Indexes.|
Immediately following the last DungeonBlock element are ( 128 - ( BlockCount * 4 ) ) bytes of padding. These values are simply padding and can be ignored. This gives each Dungeon a maximum of 32 DungeonBlock elements.