In Afghanistan, the U.S. Air Force has come up with a simple solution to supplying many army and marine bases with supplies by parachute, accurately and without using expensive GPS guided parachute rigs. The new solution uses expendable (one use) parachutes for light (under 227 kg/500 pound) bales of supplies. Coming in low and slow, in a C-130, puts less stress on the cheap parachutes and insures an accurate drop. This works in most cases, because the small outposts and bases being supplied do not need large quantities of stuff during each supply mission.
This comes just in time because, in Afghanistan, there's a growing crises with supplying the troops. This is especially true as more and more American personnel enter the country, and are dispatched to increasingly remote bases and outposts. There are over 300 American bases that have to be supplied either by truck, or by air. There aren't enough helicopters to do this, and it's often too dangerous (because of the Taliban, the terrain or the weather) to do it by road. So air drops are increasingly favored. But even here, there are problems.
Often, accuracy is needed for the drops (because of the presence of hostile forces or very rough terrain). Air dropped supplies have landed, on average, within 185 meters of the aim point. However, the new GPS guided pallets can land within 50 meters of the aim point. So when greater accuracy is needed (or it has to be done at night), a GPS guided parachute rig is used. But there is now a problem with getting these GPS parachute guidance systems back. The rigs are built to survive 20-30 drops, and even though helicopters visit the isolated troops periodically, and can bring back the several hundred pounds of equipment that comprises each GPS rig, there are still too many of them stranded out there. The army is even considering using UAVs to carry cargo, and to land and recover GPS parachute rigs.
Another problem is the many mountain peaks and ridges. The GPS guided rigs go for the spot on the ground, and navigate between the aircraft they were dropped from, and that GPS locations down there, without being able to detect and avoid any mountainous terrain that's in the way. Because of this, airdrop supervisors and pilots have to carefully plan the drops. There are several solutions to this in the works, including flight planning software that will calculate the optimum altitude and location for making a drop. There are still problems with unpredictable winds (that overwhelm the guided parachute's ability to compensate.)
In most cases, the low level, light weight drops, get the job done. For other jobs, the GPS guided rigs are still available. The air force has developed JPADS (Joint Precision Airdrop System) and ICDS (Improved Container Delivery System). Both of these systems work by using parachuted pallets of supplies equipped with GPS, and mechanical controls, to guide the direction of the descending parachute to a pinpoint landing.
Before the development of GPS guided air drops, a large percentage of air dropped supplies were lost, either by falling into enemy hands, or into things that destroyed them (especially water). With the GPS delivery systems, it's possible to do night drops, which is preferred when you don't want to alert nearby enemy troops. Often, you can accurately drop pallets without the GPS systems, if you have a large flat drop zone, daylight, and calm winds. But if conditions are difficult, you now have GPS guided drops. Otherwise, a low level, day time drop from a C-130, will get the job done.