The potential applications for GPS systems go far beyond the initial project goals. Here are three diverse examples.
GPS will play a major role in the enhanced 911 Phase II FCC mandate for cellular carriers, which will require automatic cell-phone location using network-based, receiver-based, or hybrid technology. GPS-based systems will be required to determine location to an accuracy of 50 meters (with 67 percent confidence) and 150 meters (with 95 percent confidence). Cellular carriers will deploy the capability over the next few years.
Some manufacturers are going a step further by developing automated systems for accident response. Some will use airbag deployment systems to detect crashes. Others will integrate sensors such as accelerometers to gather additional information about the severity of a crash. The cellular system would automatically transmit the data to an emergency center, enabling emergency crews to reach the crash site more quickly and with better preparation, even when the driver is unable to initiate the emergency call.
The majority of commercial and recreational vessels now use GPS. Maritime applications include ship routing, traffic management, collision avoidance, and distress response. Differential GPS covers many coastlines and harbor entrances. In many cases, the accuracy of the GPS-based positioning system surpasses the accuracy of the nautical charts used by the mariners.
GPS has helped make onboard real-time ship routing a reality, enabling navigators to determine the optimal route based on the current weather, sea conditions, forecasts, and specific ship characteristics. The routine can be used to optimize a combination of travel time, fuel consumption, ship protection, and passenger comfort.
Some challenges remain—for example, the control of very large vessels in restricted waters and during berthing, especially in areas of strong tides or high winds. Integration of GPS with other devices such as underwater acoustic sensors may make these more challenging applications feasible.
Agricultural applications are naturally suited for GPS because open environments generally allow good satellite visibility. Already, GPS has been widely used in yield mapping, crop dusting, and assisted or automated steering of farm vehicles.
Yield mapping is a technique used to record the amount of crop harvested along with the real-time position of the harvesting machine. A two-dimensional yield map shows yield as a function of position, supporting decisions such as future fertilizer application rates.
An assisted steering system provides a display showing any deviation from a planned course, helping the tractor driver stay on track. An automated steering system completely relieves the driver of this task. Steering of machinery for planting, harvesting, fertilizing, and similar tasks typically requires accuracy on the order of 30 centimeters. This performance can be achieved with some differential systems or by integration of differential GPS with other sensors such as gyroscopes.