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Land Surveying

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ApplicationsApplications
Title Land Surveying
Edited by GMV
Level Intermediate
Year of Publication 2011
Logo GMV.png

Land Surveying is a technique and science of accurately measuring the distances and angles between different points, on the surface of Earth. GNSS has been used by land surveyors since the late 1980s, primarily for geodetic control networks and for photo control[1].

Nowadays, GNSS is used to determine precise locations all over the globe, in any weather conditions and at any time of the day. GNSS geodetic surveying equipment has become smaller and easier to use being faster to use than other surveying methods. GNSS is specially used for large topographic surveys where a centimeter level accuracy is enough[2].

Contents

Application Architecture

Land surveying

Land surveying usually relies on geodetic control networks that will be used as reference points and surveys are made in relation to these reference points. In detail surveys the traditional survey techniques rely on measurements from other known locations, such as the edge of properties, landmarks, or even a surveyor's stake. These land references, are subject to change over the time. With the use GNSS the coordinates can be located precisely on a worldwide reference frame and the GNSS land surveying tools produce measurements that do not rely on what happens to the surrounding land, constructions or landmarks.

Usually GNSS survey equipment use GNSS augmentation techniques to achieve the required level of accuracy. These techniques can range from the use of satellite based augmentation systems such as EGNOS or WAAS to dual frequency receivers using Real Time Kinematic (RTK). The augmentation technique is chosen depending on the required accuracy of the survey, the available equipment resources, the time required for the survey and the environmental characteristics of the surveyed site.

Typically survey grade receivers use DGNSS or Real Time Kinematic (RTK). These techniques require data from a base station with accurate and known coordinates. The base station data can be obtained from a base station network, a single public station or a own base station setup by the surveyor. Also the surveyor can chose between realtime corrections (requiring a communication link between the station and the rover) or post-processing correction.

In general terms GNSS high-end surveying equipment is more expensive than high-end traditional surveying equipment but when used for large topographic surveys where centimeter level accuracy is enough the added cost of the equipment becomes irrelevant given that it can be much faster than traditional methods. Traditional methods are still able to achieve better accuracies and are still the best option for surveys where: sub-centimeter accuracies are required, in situations where a clear view of the sky is not available or if vertical accuracy is important. In general, for detail surveying for construction, the traditional methods are still preferred[3].

Survey Techniques

GNSS survey techniques can be separated into the following methods[1]:

Application Examples

Land surveying makes use of several equipments such as transits, tape, theodolites and GNSS receivers. Modern instruments rely on GNSS and lasers for measurements[4].

The following companies are prominent in GNSS land surveying equipments market:

Notes


References

  1. ^ a b c Guidelines for the use of GNSS in land surveying and mapping, Royal Institution of Chartered Surveyors (RICS), Practice Standards, 2010
  2. ^ Surveying on Wikipedia
  3. ^ Nature of Geographic Information, Pennsylvania State University
  4. ^ Land surveying today site, Land Surveying and GPS
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