Function offsetPosition

offsetPosition(
    p: SlicePosition,
    dir: readonly [number, number, number],
    metres: number,
): SlicePosition
Move a geographic position by metres along a local ENU direction (small-offset tangent math — exact to widget precision for the < few-km drags a slice sees).
Parameters
- p: SlicePosition
  The starting position.
- dir: readonly [number, number, number]
  Unit ENU direction [east, north, up].
- metres: number
  Signed distance to move.
Returns SlicePosition