9,000 commercial receivers were in
use in the Gulf region. They were carried by foot soldiers and attached to
vehicles, helicopters, and aircraft
instrument panels. GPS receivers were
used in several aircraft, including F- 16
fighters, KC-135 aerial refuelers, and B-
2 bombers; Navy ships used them for
rendezvous, minesweeping, and aircraft operations.
Surveying with GPS: Probably
even more important to the surveyor
or engineer than the theory behind
GPS, are the practicalities of the
effective use of GPS.
GPS has numerous advantages
over traditional surveying methods:
1. Intervisibility between points is not
2. Can be used at any time of the day
or night and in any weather.
3. Produces results with very high
4. More work can be accomplished in
less time with fewer people.
In order to operate with GPS it is
important that the GPS antenna has
a clear view to at least four satellites.
Sometimes the satellite signals can
be blocked by tall buildings, trees,
etc. Hence, GPS cannot be used
indoors. It is also difficult to use GPS
in town centers or woodland. Due to
this limitation, it may prove more cost-effective in some survey applications
to use an optical total station or to
combine use of such an instrument
GPS Applications in
Agriculture: More and more producers today are using precision
farming techniques that can help
increase profits and protect the environment. Precision or site-specific
farming involves applying fertilizer,
pesticides, and other inputs only
where they are needed. GPS-guided
equipment is often used for variable
rate application of fertilizer (based
on soil tests) or pesticides (based on
pest survey). GPS can also be used
to develop the initial reference maps
upon which variable rate applications are based. A GPS system on a
combine with a yield monitor can be
used to develop an on-the-go yield
map or can be used to map weed
locations from the combine when
harvesting. Mounted in an airplane,
GPS can be used to guide aerial
spraying operations. This reduces
production costs, as well as environmental damage from runoff of
excess nutrients and pesticides.
GPS can be used to locate weed,
insect, or disease infestations and
monitor their spread. It can also be
used to navigate back to previously
mapped infestations to apply controls. A field map can be created
using GPS to record the coordinates
of field borders, fence lines, canals,
pipelines, and point locations such as
wells, buildings, and landscape features. The resulting field map might
be the first layer a producer would
develop for an on-farm GIS
(Geographic Information System).
Additional layers showing crop damage from hail or drought, and riparian
areas or wetlands could be mapped
using GPS. Ranchers could use GPS
to develop rangeland utilization maps
and to navigate back to previously
mapped areas or monitoring sites.
GPS Navigation on Land,
Sea, and Air: GPS is being used for
emergency response (fire, ambulance, police), search and rescue,
fleet management (trucking, delivery
vehicles, and public transportation),
and for automobile guidance systems. Recreational uses of GPS
include navigation while hiking, hunting, or skiing. GPS is even used on
golf courses to track golf carts, and
to let players know how far it is to the
center of the greens. GPS is being
used for recreational sailing and fishing, and for commercial shipping
fleet management. Assisted steering,
risk assessment, and hazard warning
systems for marine navigation are
being developed using GPS. In the
air, GPS is being used for en-route
navigation (helicopter, airplane, hot-air balloon), aircraft landing, and air-collision avoidance systems.
GPS Mapping: GPS applications in natural resource management include inventory and mapping
of soils, vegetation types, threatened
and endangered species, lake and
stream boundaries, and wildlife habitat. GPS has been used to aid in damage assessment after natural disasters
such as fires, floods, and earthquakes.
GPS has also been used to map
archaeological sites and for infrastructure (streets, highways, and utilities)
mapping, management, and planning for future growth.
GPS receivers can be hand-car-ried or installed on aircraft, ships,
tanks, submarines, cars, and trucks.
These receivers detect, decode, and
Circle #152 on the Reader Service Card.