The Second Army centralised its artillery and devised a plan of great sophistication, following the precedent set at the Battle of Arras in April. The use of field survey, gun calibration, weather data and a new and highly accurate map, much improved artillery accuracy. Systematic target-finding was established by the use of new sound-ranging equipment, better organisation of flash-spotting and the communication of results through the Army Report Centre at Locre Château. Counter-battery artillery bombardments increased from twelve in the week ending 19 April, to in the last ten days before the attack. A survey of captured ground after the battle found that of the German artillery positions had been plotted. The 2nd Field Survey Company also assisted mining companies by establishing the positions of objectives within the German lines, using intersection and a special series of aerial photographs. The company surveyed advanced artillery positions for guns to be moved forward to them and open fire as soon as they arrived.