Several artillery ammunition manufacturers are trying to develop GPS guided long range shells. Some of these projects have been underway since the 1990s. The major problem is coming up with an affordable shell. To make the GPS guided shell work, you have to have devices on board that will pop up, as needed, to change the flow of air over the shell and change its direction. Since an artillery shell is, basically, traveling at several times the speed of sound when it leaves the barrel on a pillar of hot gas, any electronics and navigation devices have to be built to survive that and keep functioning until the target is hit. This isn't difficult, but so far it has proven expensive. The justification of these gold plated shells (costing over $100,000 each, so far) is that they can be fired at longer ranges (50 kilometers or more) and carry submunitions. While the longer range is nice, the number of anti-vehicle submunitions carried in a 155mm shell is limited (usually 3-6). For that kind of money, you can send an aircraft with a JDAM. And that's the basic problem; artillery is competing with aircraft (both fixed wing and helicopters). While it may seem crass to talk of money here, the defense budget is not unlimited and the artillery people have long been competing with the aviation crowd for a larger share of the pie. Like so many things in the military, the low bidder gets the job. When artillery are firing $500 shells at targets 20-30 kilometers away, the air force has a hard time competing on price. But if there's no artillery available, the aircraft are worth their higher cost. JDAM has brought down the cost of accurate firepower. The infantry and mechanized troops are impressed with JDAMs. The ability to put a one ton bomb on a nearby enemy bunker is something army artillery can't do. The JDAM, including cost of delivery, is less than $30,000. The air force has the artillery nailed on price and performance. The artillery still has an advantage in that it "belongs" to the army troops, so it's always there and will fire where an army, not an air force, general tells it to. And while the artillery manufacturers are trying to build a cheaper "smart shell," the bomb builders are coming out with 250 pound JDAMs, some with submunitions. There will always be artillery, and a need for it, but the gunners will always have a hard time competing on price with the air force.