Five arrays are used to encode the information of the contents of each tile. These arrays are referred to as map_owner, map2, map3_lo, type_and_height and map5. The known encodings are listed in the table below. The most important value is the class of a tile, stored in the upper 4 bits of the type_and_height array.
TTD's class-specific periodic tile processing routine is called once every +256 ticks for each tile.
| Class | Meaning & details of encoding | 
|---|
| 0 | 
map5 bits 4..0: tile type:
| 00 | bare land |  | 01 | 1/3 grass |  | 02 | 2/3 grass |  | 03 | full grass |  | 07 | rough land |  | 0B | rocks |  | 0F | fields; type of fields in map3_lo bits 3..0 (legal values: 0 through 9) |  | 10 | 1/4 snow |  | 11 | 2/4 snow |  | 12 | 3/4 snow |  | 13 | full snow |  | 15 | partial desert |  | 17 | full desert | map5 bits 7..6: update counter, incremented on every periodic processing for tile types other than 03, 07, 0B and 10 and above, on wraparound the tile is updated (for fields, the type of fields in map3_lo is increased, for other types the tile type in map5 is increased)
(for snow and desert, these bits are not used, tile is updated on every periodic processing)
map_owner: owner of the tile (normally 10)
map3_hi bits 7..5: type of hedge on the SW border of the tile (1 through 6, or 0=none); bits 4..2: same for the SE border
 | 
| 1 | map5 bit 7 clear: railway track 
map5 bits 7 and 6 set: railway depot / checkpointsmap5 bits 0..5: track layout: bit set = track present:
| bit 0: | in the X direction |  | bit 1: | in the Y direction |  | bit 2: | in the north corner (direction W-E) |  | bit 3: | in the south corner (direction W-E) |  | bit 4: | in the west corner (direction N-S) |  | bit 5: | in the east corner (direction N-S) | map5 bit 6 set = with signals:
map3_lo bits 7..4: bit set = signal present:
For track in the X direction:
| bit 6: | signal in the SW direction |  | bit 7: | signal in the NE direction | For track in the Y direction:
| bit 6: | signal in the NW direction |  | bit 7: | signal in the SE direction | For tracks in the W-E direction:
| bit 4: | signal in the W direction on the track in the S corner |  | bit 5: | signal in the E direction on the track in the S corner |  | bit 6: | signal in the W direction on the track in the N corner |  | bit 7: | signal in the E direction on the track in the N corner | For tracks in the N-S direction:
| bit 4: | signal in the S direction on the track in the E corner |  | bit 5: | signal in the N direction on the track in the E corner |  | bit 6: | signal in the S direction on the track in the W corner |  | bit 7: | signal in the N direction on the track in the W corner | map2 bits 7..4: bit clear = signal shows red; same bits as in map3_loOpenTTD bits in map3_hi:
| bits 1..0: | type of signal: |  | 00: | normal signals |  | 01: | pre-signals |  | 10: | exit-signals |  | 11: | combo-signals |  | bit 2: | set = semaphore signals, clear = light signals | map_owner: owner of the track
map2 bits 0..3:
| 0 | on bare land |  | 1 | on grass, no fences |  | 2 | fence on the NW side |  | 3 | fence on the SE side |  | 4 | fences on the NW and SE sides |  | 5 | fence on the NE side |  | 6 | fence on the SW side |  | 7 | fences on the NE and SW sides |  | 8 | fence on the E side (track in the W corner) |  | 9 | fence on the W side (track in the E corner) |  | A | fence on the S side (track in the N corner) |  | B | fence on the N side (track in the S corner) |  | C | on snow or desert | map3_lo bits 0..3 = track type: 0 - conventional railway, 1 - monorail, 2 - maglev
 
map5 value C0..C3: railway depot
map5 bits 1..0 - direction: exit towards: 00 = NE, 01 = SE, 02 = SW, 03 = NW
map5 value C4..C5: checkpoint
bit 0: clear = in X direction, set = in Y direction
 
 
map_owner: owner of the depot / checkpointmap3_lo bits 0..3 = track type | 
| 2 | map5 bits 7..4 clear: road 
map5 bit 4 set, bits 7..5 clear: level crossingmap5 bits 3..0: road layout: bit set = road piece present:
| bit 0: | NW piece |  | bit 1: | SW piece |  | bit 2: | SE piece |  | bit 3: | NE piece | map_owner: owner of the roadmap2 bits 0..2: 0 - on bare land, 1 - on grass, 2 - paved, 3 - with streetlights, 5 - tree-lined, 6 - on grass with road works, 7 - paved with road worksmap3_hi bit 7 set = on snow or desert 
map5 bit 5 set: road depotmap5 bit 3: clear - road in the X direction, set - road in the Y direction (railway track always perpendicular)map5 bit 2: set if crossing lights are onmap_owner: owner of the railway trackmap2 bits 0..2: 0 - on bare land, 1 - on grass, 2 or higher - pavedmap3_lo bits 0..7: owner of the roadmap3_hi bits 3..0: track typemap3_hi bit 7 set = on snow or desert 
map5 bits 3..0 - direction: exit towards: 0 = NE, 1 = SE, 2 = SW, 3 = NWmap_owner: owner of the depotmap3_hi bit 7 set = on snow or desert (not displayed, but set internally) | 
| 3 | Town building | 
| 4 | Trees 
map5 bits 7..6: number of trees minus onemap5 bits 2..0: growth status: 0..2 - one of trees is growing, 3 - all trees are fully grown, 4..6 - one of trees is witheringmap3_lo bits 7..0: type of trees:
(note: the actually displayed set of trees depends on both type and number of trees)| 00..0B | temperate climate trees |  | 0C..13 | sub-arctic climate trees |  | 14..1A | rainforest trees |  | 1B | cactus plants |  | 1C..1F | sub-tropical climate, non-rainforest, non-desert trees |  | 20..28 | toyland trees | map3_hi bits 7..5: type of hedge on the SW border of the tile (1 through 6, or 0=none)map3_hi bits 4..2: type of hedge on the SE border of the tile (1 through 6, or 0=none)map2 bits 5..4:
| 0 | on grass |  | 1 | on rough land |  | 2 | on snow or desert; map2 bits 7..6 - amount of snow or desert (for desert always set to 3 in TTD) | map2 bits 3..0: update counter, incremented on every periodic processing, on wraparound the growth status is updated (or, if it's 3, a random action is taken)map_owner: owner (normally 10) | 
| 5 | Station tile 
map5: tile type:
| 00..07 | railway station 00..01 - open platform, 02..03 - open platform with station building, 04....07 - roofed platform
 bit 0: clear = in X direction, set = in Y direction
 |  | 08..33 | large airport 
The initial layout of a large airport is (rows in Y direction, columns in X direction):| 0B | pad 1 |  | 16..19 | runway middle |  | 1A | runway ending |  | 1C | control tower |  | 20 | hangar |  | 21 | pad 3 |  | 22 | pad 2 |  | 27..32 | radar (animated) |  | 33 | transmitter |  
1F 1B 1E 33 26 1A
09 24 0B 0C 0D 16
21 1D 23 0E 0F 17
09 22 0D 11 10 18
09 08 14 13 12 19
20 0A 15 1C 27 1A
 |  | 34..41 | small airport 
The initial layout of a small airport is (rows in Y direction, columns in X direction):| 3A..3D | field with the wind meter (animated) |  | 3E | runway south ending |  | 3F | runway middle |  | 40 | runway north ending |  | 41 | hangar |  
36 3A 40
35 39 3F
34 38 3F
41 37 3E
 |  | 42 | heliport |  | 43..46 | lorry loading area;
exit towards: 43 - NE, 44 - SE, 45 - SW, 46 - NW |  | 47..4A | bus station;
exit towards: 47 - NE, 48 - SE, 49 - SW, 4A - NW |  | 4B | oilfield |  | 4C..51 | ship dock;
4C - SW coast part, 4D - NW coast part, 4E - NE coast part, 4F - SE coast part, 50 - X direction water part, 51 - Y direction water part |  | 52 | buoy |  |  | map_owner: owner of the stationmap2: index into the array of stationsmap3_lo bits 0..3: track type for railway stations, must be 0 for all the other stations | 
| 6 | 
map5: tile type:
| 00 | water |  | 01 | coast or riverbank |  | 10..1B | canal locks 
| 10 | middle part, (SW-NE direction) |  | 11 | middle part, (NW-SE direction) |  | 12 | middle part, (NE-SW direction) |  | 13 | middle part, (SE-NW direction) |  | 14 | lower part, (SW-NE direction) |  | 15 | lower part, (NW-SE direction) |  | 16 | lower part, (NE-SW direction) |  | 17 | lower part, (SE-NW direction) |  | 18 | upper part, (SW-NE direction) |  | 19 | upper part, (NW-SE direction) |  | 1A | upper part, (NE-SW direction) |  | 1B | upper part, (SE-NW direction) |  |  | 80..83 | ship depots 
| 80 | ship depot, NE part (X direction) |  | 81 | ship depot, SW part (X direction) |  | 82 | ship depot, NW part (Y direction) |  | 83 | ship depot, SE part (Y direction) |  | map_owner: owner (for water and coasts normally 11) | 
| 7 | Void 
Tiles of this class form an invisible, one tile wide border at the south (bottom) edges of the map, so as to protect several algorithms from the consequences of a wraparound at the edges.
 | 
| 8 | Industry tile 
map5: type:
(note: this is not the same as the industry type stored in the array of industries)
 
| 00..06 | coal mine 
| 00 | wheel tower when not animated |  | 01 | wheel tower when animated; animation state in map_owner bits 5..0; map_owner bit 6 set = sound already generated |  |  | 07..0A | power station 
| 08 | chimney |  | 0A | transformer; animation progress in map_owner bits 5..2 (valid range 0..7) |  |  | 0B..0F | sawmill |  | 10..11 | forest |  | 12..17 | oil refinery |  | 18..1C | oil rig |  | 1D..20 | oil wells 
| 1D | not animated |  | 1E..20 | various stages of animation; progress of animation in map_owner bits 1..0 |  |  | 21..26 | farm |  | 27..2A | factory (temperate climate) |  | 2B..2E | printing works |  | 2F..33 | copper ore mine 
| 2F | wheel tower when not animated |  | 30 | wheel tower when animated; animation state in map_owner bits 5..0; map_owner bit 6 set = sound already generated |  | 31 | chimney |  |  | 34..39 | steel mill |  | 3A..3B | bank (temperate climate) |  | 3C..3F | food processing plant |  | 40..47 | paper mill |  | 48..58 | gold mine 
| 4F | wheel tower when not animated |  | 58 | wheel tower when animated; animation state in map_owner bits 5..0; map_owner bit 6 set = sound already generated |  |  | 59..5A | bank (sub-arctic or sub-tropical climate) |  | 5B..63 | diamond mine |  | 64..73 | iron ore mine |  | 74 | fruit plantation |  | 75 | rubber plantation |  | 76..77 | water supply |  | 78 | water tower |  | 79..7C | factory (sub-tropical climate) |  | 7D..80 | lumber mill |  | 81..82 | candyfloss forest 
| 82 | candyfloss 'trees' cut down |  |  | 83..86 | sweet factory |  | 87..88 | battery farm |  | 89 | cola wells |  | 8A..8D | toy shop |  | 8E..93 | toy factory 
| 8F | animated part; animation state in map3_lo (valid range 00..31) tile animation is started (map3_hi zeroed) on the periodic processing if field 2C in the corresponding industry array entry is nonzero
 while the animation is in progress (see the array at 04328) map3_hi holds the number of animation cycles that have already taken place; when this number reaches 8 the animation is stopped
 |  |  | 94..9B | plastic fountains (various stages of cyclic animation) |  | 9C..9F | fizzy drink factory |  | A0..A3 | bubble generator 
| A1 | generators |  | A2 | bubble capture facility; animation state in map3_lo (valid range 00..27) |  |  | A4..A6 | toffee quarry 
| A5 | animated part; animation state in map3_lo (valid range 00..45) |  |  | A7..AE | sugar mine 
| AE | animated part; animation state in map3_lo (valid range 00..5F) |  |  |  | map2: index into the array of industries
map_owner bit 7: clear = under construction
map_owner bits 4..2: construction counter, for buildings under construction incremented on every periodic tile processing
map_owner bits 1..0: stage of construction (3 = completed), incremented when the construction counter wraps around
the meaning is different for some animated tiles which are never under construction (types 01, 1E..20, 30, 58; see above)
 | 
| 9 | map5 bits 7..4 clear: tunnel entrance/exit 
map5 bit 7 set: bridgemap5 bits 3..2: 0 - railway tunnel, 1 - road tunnelmap5 bits 1..0 - direction: entrance towards: 0 = NE, 1 = SE, 2 = SW, 3 = NWmap_owner: owner of the tunnelmap3_lo bits 3..0 = track type for railway tunnel, must be 0 for road tunnelmap3_hi bit 7 set = on snow or desert 
map5 bit 6 clear: bridge ending
map5 bit 6 set: bridge middle partmap5 bit 5: clear - northern, set - southern endingmap3_lo bits 3..0 = type of track on the bridge, must be 0 for road bridgemap_owner: owner of the bridge 
map5 bit 5 clear:
map5 bit 5 set:map5 bits 4..3: land under bridge: 0 - grass, snow or desert, 1 - water 
map5 bits 4..3: transport route under bridge: 0 - railway, 1 - roadmap3_lo bits 7..4 = type of track on the bridge, must be 0 for road bridgemap3_lo bits 3..0 = type of track under the bridge, if anymap2 bits 3..0: bridge piece (0..5)
map_owner: owner of the land under bridgemap5 bits 2..1: 0 - railway bridge, 1 - road bridgemap5 bit 0: clear - bridge in the X direction, set - bridge in the Y directionmap2 bits 7..4: bridge type:
| Type | Max. speed (mph) | Description | 
|---|
 | 0 | 20 | wooden |  | 1 | 30 | concrete |  | 2 | 40 | girder, steel |  | 3 | 50 | suspension, concrete |  | 4 | 60 | suspension, steel |  | 5 | 70 | suspension, steel |  | 6 | 100 | cantilever, steel |  | 7 | 130 | cantilever, steel |  | 8 | 150 | cantilever, steel |  | 9 | 160 | girder, steel |  | A | 200 | tubular, steel | map3_hi bit 7 set = on snow or desert
 | 
| A | 
map5: tile type:
| 00 | transmitter |  | 01 | lighthouse |  | 02 | company statue |  | 03 | company-owned land |  | 80..93 | company headquarters (5 sets of 4 tiles each, updated quarterly depending on the company performance) | map_owner: owner of the object (for lighthouses and transmitters normally 10) | 
| Classes B through F are reserved. The presence of a tile in one of the reserved classes will crash TTD. |