Lire les coordonnées d'une région

et les convertir en distance et en emplacement

GRID_SYSTEM:
- unit: 100km x 100km per cell
- cell_id: [ROW_LETTER][COL_NUMBER] (e.g. P03)
- origin: bottom-left corner of cell = (0,0)
- axes: x=right, y=up, unit=km, range=[0,100]

CELL_NOTATION:
- P03 → full cell, area=10000km²
- P03(75.100) → rect from (0,0) to (75,100), area=7500km²
- P03(0.0) → null surface
- P03(100.100) → equivalent to P03

ZONE: sum of all listed cells and partial cells.

GRID:cell=[LETTER][NUMBER],100x100km,origin=bottom-left(0,0),x=right,y=up; NOTATION:P03=full(10000km²),P03(x.y)=rect(0,0)→(x,y)km,P03(0.0)=null,P03(100.100)=P03; ZONE=sum of cells.