# `Sidereon.Terrain.MmapTerrain.TerrainGeoidModel`
[🔗](https://github.com/neilberkman/sidereon-ex/blob/main/lib/sidereon/terrain/mmap_terrain.ex#L303)

Geoid tier used for terrain orthometric-to-ellipsoidal conversion.

# `t`

```elixir
@type t() :: %Sidereon.Terrain.MmapTerrain.TerrainGeoidModel{
  geoid: Sidereon.Terrain.MmapTerrain.Egm96FifteenMinuteGeoid.t() | nil,
  tier: :egm96_one_degree | :egm96_fifteen_minute
}
```

Terrain geoid model.

# `egm96_fifteen_minute`

```elixir
@spec egm96_fifteen_minute(Sidereon.Terrain.MmapTerrain.Egm96FifteenMinuteGeoid.t()) ::
  t()
```

Use a caller-supplied EGM96 15-minute grid.

# `egm96_one_degree`

```elixir
@spec egm96_one_degree() :: t()
```

Use the embedded EGM96 1-degree grid.

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*Consult [api-reference.md](api-reference.md) for complete listing*