01. INTRODUCTION
Satellite navigation systems has become integral part of all
applications where mobility plays important role. These functions will be at
the heart of the mobile phone third-generation (3G) networks such as the UMTS.
In transportation systems, the presence of receivers will become as common as
seat belts or airbags, with all car manufacturers equipping their entry-level
vehicles with these devices.
As for the past developments, GPS launched a variety of
techniques, products and, consequently, applications and services. The
milestone of satellite navigation is the real time positioning and time
synchronization. For that reason the implementation of wide-area augmentation
systems should be highlighted, because they allow a significant improvement of
accuracy and integrity performance. WAAS, EGNOS and MSAS provide over US,
Europe, Japan a useful augmentation to
GPS, GLONASS and Galileo services.
GNSS development has an interesting aspect due to its
sensitive nature. Considerable events or developments are always subject to a
couple of differentiators: technological developments and political decisions. GPS
and GLONASS in all stages of improvements are strictly related to those
differentiators. The approval and startup of the European Galileo program is
considered by far the most real innovation. Technological and political
decisions in Galileo substantiate that interoperability and compatibility must
be reached in the forthcoming years. Such issues are the true GNSS improvement
for the benefit of institutions and organizations.
GNSS applications in all fields will play a key role, moving
its use from the transportation domain to multimodal use, outdoors and indoors.
It is expected that GNSS will increase significantly the precision in position
domain.
The concept of reference system for navigation is essential
since all the applications of GNSS are related to the coordinate system used.
The main application of GNSS is focused on the potential of to determine the
position in the Global reference system anywhere any time on the Globe in a
simple, fast and cost-effective manner. The integration between GNSS and other
related technologies such as telecommunications (GSM, GPRS, UMTS), the
Geographic Information Systems (GIS) and Inertial Navigation System (INS), has
created numerous applications that needs more time to be discussed in details.
Many research efforts have been exerted in order to find each new applications
to promote the quality of our life using the GNSS benefits
The GNSS consists of three main satellite technologies: GPS, GLONASS, and Galileo. Each of them consists mainly of three segments: (a) space segment, (b) control segment, and (c) user segment. These segments are almost similar in the three satellite technologies, which all together make up the GNSS. As of today, the complete satellite technology is GPS technology, and most of the existing worldwide applications are related to the GPS technology. The GNSS technology will become clearer after the operation of Galileo and the reconstruction of GLONASS in the next few years.
The ground stations use radar to make sure they are actually
where we think they are. A receiver, as you might find in your phone or your
parent's car, is constantly listening for a signal from these satellites. The
receiver figures out how far away they are from some of them.
Once the receiver calculates its distance from four or more
satellites, it knows exactly where you are. Presto! From miles up in space your
location on the ground can be determined with incredible precision! They can
usually determine where you are within a few yards of your actual location.
More high-tech receivers, though, can figure out where you are within a few
inches!
Land
surveying involves gathering information about the positions of certain points
as well as the angles and distance between them. Through the use of certain
instruments, surveyors can create maps, establish property lines, and gather
important information for architects, engineers, and developers.
The
accuracy of land surveying measurements is dependent on the quality of the
instruments used to gather the data. With the invention of GPS technology, land
surveyors are now able to make complex calculations more quickly and accurately
than ever before.
How Is
It Used in Land Surveying?
GPS
stands for global positioning system, and it uses signals from satellites to
pinpoint a location on the Earth’s surface. In addition to transmitting
information about location, GPS can provide data about velocity and time
synchronization for various forms of travel. GPS uses at least 24 separate
satellites in a system that consists of six Earth-centered orbital planes, each
having four satellites.
Generally
speaking, GPS has five key uses:
·
Determining a
position (location)
·
Moving from one
place to another (navigation)
·
Monitoring the
movement of a person or object (tracking)
·
Creating a map of
an area (mapping)
·
Making precise
time measurements (timing)
The
Global Positioning System was originally developed for military use but has
been readily available for civilian use since the 1990s. In addition to its use
in mobile devices and car navigation systems, GPS is used for land surveying.
Surveying
was one of the first commercial adaptations of GPS technology. It can provide
accurate latitudinal and longitudinal location information regardless of
weather conditions and without the need for measuring angles and distances
between points. Though GPS makes surveying possible in nearly any location, it
does have its limits.
What Are the Best GPS Instruments for
Land Surveying?
GPS
survey equipment makes it possible to obtain location, distance, and height
measurements almost instantaneously – the only requirement is that the
instrument has a clear view of the sky to receive signals from GPS satellites
clearly. When used properly, GPS for land surveying offers the highest level of
accuracy and is much faster than conventional surveying techniques.
Different
types of GPS land survey equipment are used for different purposes, though
there are three methods of GPS measurement used most often by surveyors:
Real-Time Kinematic (RTK) Observations – In this method, one receiver remains open
over a known point (the Base Station) while another receiver moves between
different positions (the Rover Station). Using a radio link, the position of
the Rover Station can be calculated within a few seconds, ensuring a similar
level of accuracy to baseline measurements as long as they are within 10km of
the Base Station.
Certain
instruments are required for proper implementation of GPS land surveying
methods. Here is a quick summary of the most common GPS land survey
instruments:
GPS
Receiver – This instrument is required to
receive signals from GPS satellites in order to make calculations. These
instruments come with a variety of optional features such as multiple band
channels, built-in Bluetooth and Wi-Fi technology, and OLED displays.
GPS Poles – Used to mount GPS surveying equipment,
these poles are typically lightweight but durable and come in different
lengths.
GPS Bipods/Tripods – For greater stability in mounting GPS
equipment, bipods and tripods come in adjustable lengths and numerous sizes.
GPS Antennae – This piece of equipment makes it possible
for GPS systems to receive signals from satellites. Many systems come with an
internal antenna, but you can purchase external antennas to boost the signal.