The presence of SA affects the acceptance of GPS by recreational boaters and some commercial users, and limits the ability of the Coast Guard's DGPS service to provide important safety-related information to its users.

The civil land transportation sector of the nation's economy has generally been slow to adopt high technologies from other sectors such as aerospace or electronics. Recently, however, this trend is beginning to change due to an increased focus on initiatives such as the Intelligent Transportation System (ITS), which adapt defense-related technologies for uses in the civilian community.²⁸ More specifically, land transportation applications of GPS are growing rapidly, triggered by ever cheaper and more sophisticated equipment, an accelerated maturation of technology, widely available differential augmentations, and competition for economic and environmental responsiveness. All modes of land transportation, including trains, trucks, automobiles, all-terrain vehicles, bicycles, backcountry skiers, hikers, and even pedestrians, have applications in which safety, position-location, and navigation are important, and have users who are therefore willing to use low-cost GPS, DGPS augmentations, or other comparable systems.

The trucking and railroad industries are currently the dominant land users of GPS for vehicle location and navigation, in part for reasons of competitive advantage in meeting the needs of just-in-time manufacturers and goods distributors. As on-time delivery becomes increasingly important to U.S. manufacturers and distributors, the trucking and rail industries and the international freight industry will require the ability to locate not only their vehicles or shipping containers, but also the components of their cargo when it consists of divisible elements, such as the packages handled by United Parcel Service or Federal Express. This must be accomplished with ever-greater accuracy and in near real-time. The tentative quantitative requirements for these GPS applications are listed in Table 2-6.

One of the largest near-term markets for GPS will probably be for automobile and light truck navigation and position-location. This market can evolve in a number of ways, since the automobile is used for a variety of purposes. On-board GPS and CD-ROM map systems are already being utilized by several rental car agencies, and at least one major U.S. automobile manufacturer already offers a GPS-based navigation system to its customers as

an option.²⁹ It also is estimated that over half a million automobiles owned and operated in Japan already carry a GPS-based automobile navigation system.³⁰

Although the final systems architecture and standards for the nation's ITS program have yet to be determined, the FHWA (Federal Highway Administration) anticipates that GPS will be an important component.³¹ Potential ITS applications for GPS, in addition to vehicle navigation and position-location, include collision avoidance and control, vehicle command and control, automated bus stops, automated toll collection, accident data collection, a number of commercial vehicle regulatory activities, and ITS infrastructure management. Tentative requirements for these applications are included in Table 2-6.

GPS can also be used for the automatic guidance of farm vehicles engaged in precision farming. Also known as prescription farming, or site-specific crop management, precision farming gives the farmer the ability to apply precise amounts of fertilizer and pesticide to exact field locations based on the type of crop planted and the soil composition, potentially improving both the efficiency and cost-effectiveness of these operations. The positioning and navigation accuracy required for precision farming, as shown in Table 2-6, can only be met with local-area DGPS.

Much of the growth in the so called low-end, personal GPS receiver market can be attributed to transportation-related recreation activities involving both vehicles and pedestrians. Examples include "off-roading" with four-wheel drive vehicles, back-country skiing, mountain climbing, bicycling, hiking, and even golfing.³² For those activities in which the potential for "getting lost" is high, and search and rescue services are often required as a result, GPS is much more than a useful gadget; it is a potentially life-saving device.