Note: Interpretation of the type word is dependent on the class of the seed.
This topic describes flat seeds of class 11h The flat seed class specifies ground terrain that is flat with the same altitude across the seed. The terrain can be of varying types including water, crops, desert, and so on. The table included in this topic describes the different types of flat seeds.
There are two sizes of flat seeds. The size of the seed represents how large an area on edge is covered by one 256x256 visual texture. The large seeds are effective for vast expanses that will be viewed from high altitude; the smaller seeds show more detail. However, the smaller seeds cyclically repeat four times as often which gives a patterned effect on the ground.
The least-significant byte of the type word defines the ground cover type. The most-significant bit of the least-significant byte differentiates between large and small seeds. The most-significant bit is unused and is set to zero. The following table shows the type word value and type (and description, where necessary) for flat seeds.
| Type word value | Type | Description |
| Large Seeds (64km) | ||
| 00h | Water | |
| 01h | Broadleaf | |
| 02h | Needle leaf | |
| 03h | Tropical | |
| 04h | Crops | |
| 05h | Prairie | |
| 06h | Arid | |
| 07h | Desert | |
| 08h | Tundra | |
| 09h | Ice | |
| 0Ah | Swamp | |
| 0Bh | Paris | |
| 0Ch | Munich | |
| 0Dh | Variation on arid seed type | |
| 0Eh | Variation on arid seed type | |
| Small Seeds (16km) | ||
| 80h | Plain green | |
| 81h | Small city | |
| 82h | Medium city | |
| 83h | Suburban 1 | |
| 84h | Lake | |
| 85h | Suburban 2 | |
| 86h | Suburban 3 | |
| 87h | - | |
| 88h | Rolling hills | Special-case hill generator. Generates a 4x4 mountain grid, with latitude/longitude repeatable random peaks between 0–750 ft. that are green in color. This seed only works properly as a level 13. If you make the seed a level 12 or higher or if the front-end processor combines 2 or more of these seeds, a single level 13, 4x4 hill mesh will be centered in the middle of the combined area, and the rest of the seed will be solid green. |
| 89h | Sand dunes | Special-case hill generator. Generates a 4x4 mountain grid, with latitude/longitude repeatable random peaks between 0–750 ft. that are tan in color. This seed only works properly as a level 13. If you make the seed a level 12 or higher or if the front-end processor combines 2 or more of these seeds, a single level 13, 4x4 hill mesh will be centered in the middle of the combined area, and the rest of the seed will be solid green. |
| 8Ah | High-rise | |
| 8Bh | Medium-rise | |
| 8Ch | Urban | |
| 8Dh | Urban/Suburban |