GNSS Markets and Applications - Understanding GPS: Principles and Applications - page 650

12.4 Recreational Markets for GNSS-Based Products

Some obvious recreational applications of global positioning technology include
hiking and orienteering. SAR teams can also make good use of the technology. Some
applications are not so obvious, and it is here that the assertion that there are more
uses for GPS than we can imagine is put to the test. Several organizations are devel-
oping positioning systems for golfing applications. Differential corrections are
required, as accuracy of a few feet is needed. Course managers are attracted to the
idea as a method to speed up play and improve the utilization of an existing
resource. Receivers have been put on golf carts to display from a database the dis-
tance to the green, to the pin, and to any hazards that may be of interest from a given
location.
At outdoor parks, tourists can use a GPS device that will allow them to conduct
a self-guided tour without any external signs or references. At each designated spot,
vignettes can be automatically triggered by the GPS unit and direct tourists based on
their present position and knowledge of where they have been previously. Recently,
recreational and commercial users were able to display digital maps on their
GPS-equipped cell phones via a service provided by Cellular Telephone Industry
Association members.
GPS receivers are small enough to be worn on the wrist. This has opened up
applications for joggers to keep track of their location, speed, and distance, as well
as for keeping track of children and for blind people to navigate [13, 14].

12.5 GNSS Time Transfer

The fact that GPS is based on accurate time references implies that the signals can be
used for the synchronization of very accurate clocks and timing standards. Each sat-
ellite has multiple atomic clocks on board, and each is frequently updated to system
time. A prime application of this accurate timing capability is in the control of data
communications networks like the Internet, where data packets time-share the same
communications bandwidth. Receivers and transmitters can be synchronized,
reducing the data overhead required of the system. Other applications include syn-
chronized switching of power grids and timing of racecars. An example of this was
reported in August 2004 in Network World at the July 2004 NASCAR race at the
New Hampshire International Speedway. Over 90,000 fans watched as GPS was
used to time the racecars' performances. Data from each car, including its speed,
position, time, braking, throttle position, and rpm, were sent five times per second
to a BS and thence over the Internet and pay-per-view TV. There are several manu-
facturers of equipment dedicated solely to the extraction of accurate time from the
GPS signal.

12.6 Differential Applications and Services

Perhaps the largest submarket involves the provision and use of differential
corrections.