When working with 2D maps, coordinates are always expressed in X and Y. Adding a 3rd dimension also adds the Z-coordinate, which typically stands for height.
However, when working with vertical grids (for measurements, visualizations on building facades or the sides of 3D polygons, etc.) I don't know which coordinates to mention in order to express what I mean.
Is it 'X and Z' or 'Y and Z'? Or does it become 'X and Y' again since there is no 3rd dimension?