Grid cell size
Grid cell size is a setting that stores the size of grid cell of the session, and is set for each active Grid Overlay.
Grid Overlays can be inactive. Changing the grid cell size does not change the grid cell size of inactive Grid Overlays. However, activating a Grid Overlay will require the recalculation of its results when their Grid Cell Sizes are different.
The name of the setting is 'GRID_CELL_SIZE_M' and has a default value of 2 meters.
Grid Accuracy Threshold
As the grid size decreases (and thus more cells exist in the project), calculations will take longer to complete. Under normal circumstances, when a calculation is based on geographical parameters, all contents of the cell are checked and all objects relevant to the calculation are taken into consideration based on how much of the cell is covered by it. When the grid size falls below this threshold, the method for determining these parameters changes. Instead, the exact center of the cell is checked, and if relevant data is found it is taken into consideration as if it were present in the entire cell. This is less accurate, but allows the calculation to complete faster.