Frequently
Asked Questions
What
is GPS?
What is DGPS?
How accurate is GPS?
What are some typical GPS applications?
How can GPS improve my business?
What is NavCom's relation to John Deere?
Will my GPS work under trees or in a tunnel?
How does weather affect the GPS
signal?
What are the effects of solar activity
on GPS?
What
is GPS?
The
Global Positioning System (GPS) is a network of nominally 24 satellites
funded by and maintained by the United States Department of Defense.
These satellites continually orbit the Earth transmitting navigation
messages, thus providing continuous and worldwide three-dimensional
positioning, velocity and time information. For more detailed information,
please refer to the related links section
of our site.
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What
is DGPS?
Differential GPS is the process of applying correction data to the
satellite positioning data to correct for bias errors. Differential
corrections are determined by calculating the known and observable errors
between a known location or reference site and the positioning data
provided by the satellite signal. This allows for significant improvements
in accuracy of precise positioning. Our StarFire™
Network is a global system providing DGPS corrections which can
be used in real-time or with post-processing techniques.
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How
accurate is GPS?
It is hard to generalize on the accuracy of GPS since it is highly
dependent on the type of receiver being used. There are, however, many
factors that can improve accuracies such as whether the receiver uses
single or dual frequency, differential corrections, and multipath mitigation.
Now
that Selective Availability (SA) has been turned off, the typical accuracy
for a stand-alone GPS receiver is between 2 to 5 meters.
Higher
accuracies can be achieved by using local area differential (1
base station covering 100 mile radius.) With local area differential,
a good receiver should yield accuracies of about 30cm horizontal. In
this scenario, the NCT-2000D™
dual frequency receiver yields accuracies of 10cm horizontal!
With
wide area differential, coverage is expanded over a continent
by using a global network of ground reference stations, such as our
StarFire™ Network or the WAAS
navigation system. A good receiver in this case gives accuracies between
0.5 – 1.5 meters. With NCT’s proprietary dual frequency network and
state of the art dual frequency
navigator, our receiver yields 0.25meter accuracy!
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What
are some typical GPS applications?
GPS is a fast growing, technologically sophisticated field, with
potential applications in many different industries. The most common
civilian applications to date have been land, air and marine navigation,
and surveying. More recent applications include aircraft precision approach,
robotics, IVHS (intelligent vehicle highway systems), construction,
resource extraction, and geographic information systems (GIS). Developments
in differential GPS mean increased reliability and even more widespread
possibilities.
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How
can GPS improve my business?
There are an increasing number of applications for GPS as the technology
improves and becomes more readily available. Depending on the industry,
the implications of GPS technology are vast. Obviously, the survey and
GIS markets depend on its reliability and accuracy, and we will continue
to service these areas and work toward advancement of the technology
for those applications. There are, however, a growing number of industries
turning toward GPS technology to run their businesses more efficiently
and create new businesses. The agricultural
industry, for example, is being revolutionized by the implementation
of precision farming enabling, at minimum, highly accurate yield maps
of soil/harvest conditions of an area, thus leading to more precise
farm care, less waste and greater profit. Mining, fleet management,
construction equipment, machine control and various offshore marine
industries are just a few industries discovering new applications and
benefits of GPS from employee safety to bottom line profits. NavCom’s
commitment to producing the highest quality products and services is
not limited to one niche market. As our customer’s businesses are very
diverse, it is important to us to remain flexible in order to design
and customize for customer-driven applications.
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What
is NavCom's relation to John Deere?
Since our inception in 1994, we enjoyed a long-standing client relationship
with Deere during which time we developed high precision receivers for
their agricultural markets. As the world leader in the agricultural
industry, John Deere has always had the tradition of excellent products
and leading technology - a tradition that, while NavCom is obviously
a much younger company than Deere, has been a fundamental building block
of our company. In 1997, Deere acquired forty percent of the company,
and in November 1999 we were fully acquired
by Deere forming their Special Technologies Group.
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Will
my GPS work under trees or in a tunnel?
For most applications, GPS is by its very nature strictly a line-of-sight
system, i.e. it needs a clear view of the sky. Therefore the receiver
will not be able to navigate if the signal path from the GPS satellite
to the receiver’s antenna is blocked by, e.g. buildings, tunnels, or
natural obstructions.
However,
signal attenuation due to foliage will not necessarily render a GPS
receiver useless. Depending on the signal processing techniques used,
it is possible to track GPS satellites under dense canopy even with
very low signal strength. The NCT-2000D™
uses several different techniques such as proprietary multipath rejection,
multibit sampling, and patented L2 tracking technology to improve its
signal tracking capability.
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How
does weather affect the GPS signal?
In general, GPS is an all-weather system not affected by rain,
snow, or other weather-related disturbances. However, there are a number
of possible effects of thunderstorms on the GPS signals and GPS receivers.
The largest effect is caused by a direct or near miss lightning strike,
which could permanently damage the GPS receiver. To protect GPS receivers
in fixed installations, lightning protection is recommended. The second
possible effect of lightning is related to electromagnetic noise generated
by the multitude of lightning strikes in a nearby thunderstorm interfering
with the differential GPS radio link (if not L-band). There are no measurable
effects on the GPS receiver or GPS signal of nearby lightning strikes.
However, snow or ice if piled up on a GPS antenna may absorb some of
the GPS signal reaching the GPS antenna, thus reducing the sensitivity
of the GPS receiver system.
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What
are the effects of solar activity on GPS?
Solar cycle
#23 will peak in the year 2000 and last for more than a year. The
resulting ionospheric disturbances will cause significant, random errors
for single frequency users, while dual-frequency users will be able
to measure the errors directly and compensate for it!
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