voxcity.utils.GridProjector
===========================

.. py:class:: voxcity.utils.GridProjector(geom: GridGeom)

   Projects between lon_lat (WGS84) and uv_m (local grid metres).

   The 2×2 affine A maps (u_cell, v_cell) → (dlon, dlat)::

       A = [[u_vec[0]*du_m, v_vec[0]*dv_m],
            [u_vec[1]*du_m, v_vec[1]*dv_m]]

   where (du_m, dv_m) = adj_mesh.  A⁻¹ is pre-computed for O(1) calls.
   Accepts both scalars and numpy arrays.


   .. py:method:: lon_lat_to_uv_m(lon: ArrayLike, lat: ArrayLike) -> tuple[ArrayLike, ArrayLike]

      lon_lat → uv_m.  Accepts scalars or numpy arrays.

      Returns (u_m, v_m) where u_m = metres along u_vec from grid origin,
      v_m = metres along v_vec from grid origin.
      Cell (i, j) occupies uv_m in [i*du_m, (i+1)*du_m) × [j*dv_m, (j+1)*dv_m).



   .. py:method:: uv_m_to_lon_lat(u_m: ArrayLike, v_m: ArrayLike) -> tuple[ArrayLike, ArrayLike]

      uv_m → lon_lat. Exact inverse of lon_lat_to_uv_m.



   .. py:method:: lon_lat_to_cell(lon: ArrayLike, lat: ArrayLike) -> tuple

      lon_lat → (i, j) integer cell index.

      Uses floor division — safe for boundary points and negative coordinates.
      Scalar inputs return Python ints; array inputs return int ndarrays.



   .. py:method:: cell_to_lon_lat(i: ArrayLike, j: ArrayLike) -> tuple[ArrayLike, ArrayLike]

      Cell centre (i+0.5, j+0.5) → lon_lat.