# Georeference

> Talos next · Since next

Where the scene is on the earth.

Frame (fixed): a transverse Mercator plane centred on (lat, lon), scaled to groundHeightM; +x grid east, +y up, +z grid south. A map plane, not an east-north-up tangent plane: convert round-earth positions through latitude, longitude and height.

## Fields

| Field | Type | Required | Default | Allowed values | Description |
|---|---|---|---|---|---|
| `lat` | `number` | yes |  |  | Latitude of the scene origin, degrees (WGS84), north positive. |
| `lon` | `number` | yes |  |  | Longitude of the scene origin, degrees (WGS84), east positive. |
| `heightM` | `number` | no | `0` |  | The height that local y = 0 stands for, in the scene's vertical datum (DEM heights are usually above the geoid). Default 0. |
| `groundHeightM` | `number` | no | `heightM` |  | Height of the ground around the origin (m); lengths on the scene's plane are true at this height. Default heightM. |
| `geoidSeparationM` | `number` | no | `0` |  | Ellipsoid height minus geoid height at the origin (EGM2008 N, m); added when converting to ECEF (DIS). Default 0. |