In order to be in a position to choose from the various GPS solutions
that are present in the consumer marketplace, it is necessary to have a
reasonable understanding of what they can offer, as well as what the user is
expecting from the solution.
There are several components that need to be looked at. There is the GPS
receiver (or antenna) itself, which plays an important part. Then there is
the portion of the system which uses the received information to estimate
where the device is located on an internal map.
Then there are the various capabilities for route planning and recording,
which vary from unit to unit. Finally, the display portion of each solution
type can vary considerably, from limited location information to full color
three dimensional maps of the immediate surroundings and advised route.
How it Works
All GPS solutions are based on the same premise, and it is a good idea to
at least be aware of the underlying technology so that an informed decision
can be made as to which application of the GPS technology is appropriate for
the user in question.
GPS receivers use signals from satellites which orbit the Earth at known
positions. Each satellite has a unique identification code and sends a
signal which the GPS receiver can use to calculate the distance from the
device to that satellite.
Much like regular orienteering triangulation, this allows the software to
estimate its own position from several (at least 3, preferably 4 or more)
signals, by finding the point in space at which the spheres representing the
distance from each satellite intersect.
From this location information, the software can then pinpoint the
devices location on a map and use the information for a variety of
operations, from simply displaying the location, to adjusting a proposed
route based on the actual position of the device compared to the desired
position.
Applications
There are three broad classes of application - road, hiking and maritime
- and each is further subdivided into other types which offer different
features depending on the exact use to which they will be put and the
environment that they will be operating in.
One important thing to remember is that this technology does not allow
the transmission of actual mapping data via the satellites. It is purely
concerned with the location of the device.
The first application we shall look at is the in-car (or in-vehicle) GPS.
These units need to be reasonably accurate, reliable, and contain details of
all the roads, and important addresses (gas stations, railroads etc.) and
points of interest for the region in which the device will be operating.
These devices may be part of the in-vehicle entertainment system, which
ties them to a single vehicle. Or installed under the dashboard. Obviously
the drawback is that they are not able to be removed from the vehicle.
Portable devices suitable for in-vehicle use exist, and offer a great
alternative to those which are integrated within a particular vehicle.
However, they will not be able to override the in-vehicle entertainment
device (CD player, etc.) and so the voice commands might be drowned out by
the music.
Then there are portable devices which are designed for general use, which
have a limited road database, and reasonable terrain information. They are
small enough to be carried in the palm of your hand.
However, a recent trend has seen PDA manufacturers attaching a GPS
antenna, and providing sophisticated software and maps which use the power
of the PDA to give an excellent solution. They might not be rugged, but they
do provide a very good base for both in-vehicle and general navigation.
Rather than having a direct connection, many PDA - based GPS solutions
use Bluetooth as a means to communicate with the GPS receiver. This makes
them more easily installed in, and transported from, vehicles.
Finally, maritime units need very specific features, not least being that
they should be waterproof, and containing additional information that can be
plotted on nautical charts. Their maps are also very specific, giving
undersea elevations as well as navigable channel information.
This includes devices such as fishfinders, which build other fishing
related features into the basic GPS unit. A fishfinder is very useful for
positioning, tracking and helping the fishing enthusiast to locate schools
of fish at sea.
Associated technologies such as GPS Tracking have also evolved, where the
user wears a watch which relays their position via radio to a central
control center. This tracking information is then used in conjunction with
an alert system to track anything from vehicles to people.
Updates & Mapping
When choosing a GPS, it is important to bear in mind that each type will
be updated in a different way. For example, dedicated in-vehicle units tend
to be updated via a CD, which has to be purchased from the road map data
supplier.
Those which are attached to a PDA, as well as most handheld dedicated GPS
devices, are usually updated via a PC. They also need maps, but said maps
can usually be acquired at a much lower price than the dedicated branded
ones needed for other systems.
Being able to update the device easily and at a reasonable cost is a very
important part of the decision process; unlike other consumer devices that
you purchase, the cost of ownership of a GPS unit is proportional to its
usefulness.
The less you spend on maintaining it, the less useful it becomes since
the road networks are always changing. This is perhaps less important for
devices aimed at hiking and orienteering, but could be a factor in deciding
whether a multi-function device is better than one dedicated to a specific
use.
Specific software vendors have solutions for preparing maps which can be
uploaded into the GPS unit. For example, many are based around the mapsource
system which permits users to define their own maps, perhaps scanned from a
real one, in order to get the most out of their GPS.
Accuracy & Portability
If accuracy is paramount, then it is also important to choose a unit that
is equipped with a WAAS (Wide Area Augmentation System) capability assuming
it is available in the region the unit is being used.
This is a satellite service which provides additional correction
information to the GPS receiver which enables it in order to increase its
accuracy.
WAAS equipped devices might be especially useful for road users and those
involved in either door-to-door selling, or providing a service which
requires them to be able to pinpoint their position right down to a few
feet.
On the other hand, it is useless to purchase a WAAS capable system if the
service is not available in the area in which the device is to be used.
If portability is a key part of the decision process, then it will
usually be a trade-off against accuracy, whether that accuracy stems from
poor GPS signal acquisition, or less powerful software coupled with a less
detailed map.
The Choice
In the end, the choice is reasonably straightforward – buy the most
expensive GPS that fits your needs; if price is a deciding factor, then buy
the most expensive one you can afford which fits your needs.
Try to think about the following:
- Portability
- Features
- Mapping and Updating
- Environmental Features
Portability is affected by weight and size, as well as the antenna. This
could have an effect on the features that the device offers – clearly if
the screen is tiny, and the whole unit is about the size of a cell phone,
then some advanced features will not be fitted.
The mapping and updating capabilities are also important. Should it be
able to accept any old map from a PC, or is it enough that the unit is
replaced after 5 years? Technology moves almost as fast as the roads are
updated, so this could be an option.
Finally, are there any specific environmental options that are needed,
such as waterproofing, rugged shock-proof design, or other features that
make one device more attractive than another?
Answering these questions will help determine what type of GPS receiver
that is right for you, and at the right price.
About the Author:
Guy Lecky Thompson is a successful freelance writer offering guidance and
suggestions for consumers regarding GPS
tracking, GPS,
GPS maps and tracking
devices. His many articles give information and tips to help people save
money and make smarter decisions.
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