GPS Total Station- Benefits and Drawbacks

What is a GPS Total Station
GPS stands for "Global Positioning System." It is a technique for determining positions and elevations on earth. For maximum accuracy, a GPS total station takes help of a number of satellites placed into orbit. Depending upon the quality of the GPS survey equipment, the accuracy can differ from about 30 meters (plus/minus) for inexpensive hand held receivers, to only 1 centimeter (plus/minus) for sophisticated systems using a base station located at a known position on earth to give a reference signal. This technique is known as "differential processing". GPS v/s Total Station
The price of a GPS total station is about 2 to 3 times that of a regular total station. However, the extra investment can prove beneficial as you save a lot on its operating cost. In the debate- GPS v/s Total station- an analysis of the advantages and disadvantages of GPS total station will go a long way to help you decide what to buy- GPS total station or not?
Benefits of GPS Total Station
The most crucial advantage of a GPS total station is that it brings your costs to the minimum level possible through these following ways.
•When you use a total station, you require professionally surveyed ground markers. These markers are used as fixed reference points known as control points. You require a number of control points- each one of which should be within line of sight to at least one other control point. However, when you use a GPS total station for mapping, you need no control points. As such, you save the money you would have spent for hiring a surveyor to install the markers.
•When using a total station, a whole team is needed for the operation. A GPS total station brings this number to a single person who could perform the whole operation thus saving on manpower.
•The dual frequency GPS total stations can even be used in any weather condition, as they come with a radio communication link between GPS receivers.
•Many of the GPS total stations now are equipped with softwares
providing powerful tools for site calibration, coordinate geometry calculations and other features for maximized productivity.
•The most advanced GPS total stations also have multitasking operating system
that allows several screens to be opened simultaneously without hindering the GPS surveying activities or satellite lock.
•During the survey, the "job map" display- installed in many GPS total stations- lets you see a real-time graphic review of what has been surveyed or staked out. This avoids costly site revisits.
Drawbacks of GPS Total Station
If you just go for a GPS total station and not for the most advanced one, then you you must also consider the following disadvantages of a GPS total station.
•A GPS total station almost is non workable in areas with lots of big trees or buildings. Tree Canopies, if wet, can affect GPS measurements, thus reducing their accuracy or increasing the time duration for measurement. However, there is also a solution for this- a laser range finder and a built-in electronic compass can automatically provide the offset data to the GPS.
•A GPS system can also shut down due to periodic loss of satellite signals. However, you can always determine beforehand about the time when satellite coverage will not be adequate with the help of the GPS vendor and schedule your work according to these time periods of low satellite availability.
•In spite of providing high accuracy, a GPS system is not essentially consistent. Changes in signal conditions can make the results vary. Generally though, you can expect GPS accuracy of less than one meter most of the time when using real-time or post-processing correction and on the order of 1 centimeter most of the time when using your own base station for correction. One-meter accuracy is sufficient for mapping most of the woody plants while it is not so for mapping smaller and tightly spaced plants. However, smaller plants may be added manually by sketching in their positions in relation to the woody plants and hardscape features. As far as a total station is concerned, its accuracy does not vary provided it is properly maintained. Accuracies on the order of 1 - 10 cms can be consistently received with a total station based on the skills of the operator surveyors.
If not going for a very sophisticated GPS total station, the best idea would be to buy both- a total station and a GPS total station- depending upon the volume of work you have to perform. A total station can be taken anywhere without the concern for weather or vegetation and it is great to work with a GPS total station in wide open spaces that also increases your productivity!



With Regards,

Sebastian

G.M. Technical

Nunes Instruments

645 Hundred Feet Road,

Coimbatore. 641012.

Tamil Nadu

India,

Web: www.nunesinstruments.com

Mail: info@nunesinstruments.com



Mobile: 09345226022