With the spread of firearms, the "bombardier" became a military technician highly specialized in the deployment of ordnance. To set cannon fire precisely, accurate measurements had to be made with specific instruments: quadrants and magnetic compasses for calculating the distance of the target, and squares for determining the elevation of the bombard, compasses with curved legs for the gauge of projectiles, graduated rods to weigh cannonballs and calculate the amount of gunpowder to be used.