GPS Engineering Survey

Geographic Positioning System (GPS) applications are widely used in engineering surveys such as in site surveying setting out, check and compliance surveys. The application of GPS become very complex and demanding, when it is used in engineering projects such as bridges, dams, tunnels, high rise buildings which require precise deformation measurements. In essence, GPS has been a popular tool for long term monitoring of civil engineering structures. Hence, GPS application on engineering survey implies accuracy and reliability.

As we know in engineering surveying, emphasis on error correction and accuracy is taken seriously. In other words, an engineering surveyor should know the accuracy and reliability limits of the surveying technique or method he uses. Hence, he has to use the most reliable, economical, technically appropriate measuring technology for the intended purpose.

It is important to know about the real accuracy limits of surveying methods. Thus when using GPS, one should be aware of its applicability and limitations in engineering surveys.

GPS applications use satellite technologies (which has comprehensive error correction procedures or large error budgets) which allow reliability and accuracy. The accuracy of GPS application in engineering survey depends on many factors that depend on optimal observation parameters and procedures using various standards and software systems. The accuracy and reliability of GPS in engineering surveying greatly influenced by the factors:

1) the satellite constellation system used,
2) the atmospheric condition,
3) actual measuring condition of the observed site,
4) the quality of GPS instruments used and
5) the procedures used for testing, processing and optimization of GPS data obtained from site. Hence, similar to traditional engineering surveying, accuracy management is essential when applying GPS engineering Application to surveying.

Presently the GPS applications are popularly used when developing local special geodetic networks for engineering projects. Such networks are small compared to large regionally and globally available networks. To ensure reliability accuracy of these testing models, it is essential to acquire large amount of experimental data for a considerable period. Then the data is subject to various investigation and analyses with a view to improve and optimize the observation and processing procedures.

When GPS is used for measuring heights, it may encounter constraints or limitations owing to lack of exact knowledge and the condition of the local geoid, particularly in mountain areas or proximity to tall building. In such situation, it may have to depend on observations made from different directions using multiple satellite and receivers.
Similarly, measurement of deformation needs high accuracy and require longer time and costs. In the recent past, terrestrial methods were employed in many scenarios but now these have been substituted by GPS engineering survey applications.

In the case of long term monitoring of structures, static GPS applications are widely used. It can give relative position accuracy up to few millimeters based upon the time of observation and distance of the reference station. By establishing permanent GPS stations can help you to maintain a reliable and consistent reference coordinate system in the interested location.

There are many engineering surveying firms specialized in GPS application in engineering construction.

Land Surveys Pty Ltd are one of Perth's premier surveying companies and providing surveying services and GPS mapping services in Western Australia.

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