STEP ONE: Run visibility tool with all observer points in a single shapefile.
This yields a raster showing what is visible from ANY of the obervers, but also with cell values ranging from 0 to 4, indicating how MANY observers can see each cell.
STEP TWO: Use Raster Calculator to generate a raster that only includes cells visible from 4 observers:
In my example there are only a few cells that are actually visible from all 4 observers, shown by the green cells. Black indicates not visible.
Jay
Jay
Washoe County GIS