In Flight Simulator scenery, the seed coordinate system defines the borders of the square areas known as seeds. Seeds are specified in .bgl files and in memory as seed entities. The following code example shows the structure of a seed entity; note that the seed definition includes seed type and altitude.
;SEED ENTITY OPCODE DEFINITIONS -
;OpFormatDefinition
;-----------------------------------------------------------------
;4db 4SEED ENTITY;00 opcode
;dw 0;01 longitude coord
;dw 0;03 seed type
;db 0;05 seed class
;db 0;06 seed status
;db 0,0,0;07 altitude ii.f M
;;10
The parts that make up the preceding seed definition are described in the following table.
| Part | Description |
| Opcode | The opcode byte of the value 4 indicates that this is a single seed. |
| Seed level (implicit) | Although no seed level is explicitly specified, it's implied by the location of this seed definition in the .bgl file. |
| Latitude coordinate (implicit) | Although no latitude coordinate is explicitly specified, it's implied by the location of this seed definition in the .bgl file. |
| Longitude coordinate | The seed is located at the seed coordinate longitude specified by the word at offset 01. This is specified in seed “longitude coordinate” which, along with the level on which this seed occurs, corresponds to a true longitude coordinate. |
| Seed type, class, status | These entries, at offsets 03, 05, and 06, define what the seed represents visually. For example, a seed can represent a flat forest area, a desert, a mountain, a coastal section, or even a “hole” that will be filled in with object scenery. For more information, see the topics in the Seed Types section of this SDK. |
| Altitude | The seed’s altitude above sea level (MSL), specified in “ii.f” meters format; this is a signed fractional integer. |