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GPS finding its way into the surveying toolkit

Professional surveyors are always looking for new technologies that can be helpful in their daily work. The ‘survey tool’ must be accurate, easy to use, reliable, fast and water and dust resistant. Today, the GPS technology is fully compatible with all these requisites: high-accuracy receivers are certified to provide real-time GPS measurements with centimetric accuracy, with short acquisition time (seconds), are able to fix in less than 10 seconds even in the cold start conditions. Current satellites constellations (Navstar, Glonass, the incoming Galileo and Compass) offer 24-hour coverage all over the world. It is always possible to find several satellites just above our heads! The large number of satellites in orbits around the Earth offer field operators the choice of the best configuration of satellites in the sky and enhance the quality of survey. Also, the number of broadcasted carriers by each satellite has increased: the latest generation of GPS receivers can detect, for example, the GPS L5 carrier, or increase the precision of measurements in an area where satellite reception is weak.

Field software is becoming more and more important: new protocols for differential corrections, such as RTMC 3.1, provide real time transformation information for geographical coordinates and height, with better accuracy compared to old systems. The field software must always be updated and customised for every new protocol, giving the user the ability to fully exploit the new technologies.

New technologies
A new way for GPS survey is now present in the market, not only for GIS applications, but even for high-accuracy survey. New receivers integrate in one unit the complete system: receiver, GNSS antenna, controller facilities (display and software), connections (Wi-Fi, Bluetooth, GPRS): all in one hand complete system. Even total stations are an exciting challenge for surveyors: new robotic total stations, developed using an advanced electronic technology to maximise the precision of distance measurements, allow to execute survey with only one operator on field (that means: save money). Using a GPS receiver embedded in the robotic controller, the robotic instrument can be pre-oriented to the operator‘s position, assuring a safe survey even in case of obstacles in the line of sight. Laser scanner technology is also growing considerably. With a laser scanner, it is possible to collect millions of points in few minutes, allowing civil engineers and cadastral operators a fantastic chance to process/produce in their office 3D models of objects, lands, roads, houses or store in electronic format shapes of objects of interest for cadastral, architecture, archeology and industrial applications.

It is always difficult make a prediction in a market of fast changes. New challenges and prospects for GPS survey could be summarised as some improvements in the receiver system, such as integration of inertial platform in the GPS sensor, a major use of the wireless connections of new generation, more robust and powerful and other minor improvement like tilt compensators. Other sensors will be integrated, in order to maximise the accuracy of the survey: for example humidity or temperature sensors.

GPS network expansion
Beyond the receiver’s improvements, the big challenge will be the great expansion of local GPS network, thanks to the opportunities given to the major competition between producers of CORS stations and network adjustment software. The possible uses of these permanent GPS/GNSS networks interest a wide range of scientific orders, as well as applications for territory management nowadays which is of considerable interest for the community. Surveyors, GIS users, engineers, scientists and the public at large who collect GPS data can use CORS data to improve the precision of their positions. CORS-enhanced, post-processed coordinates approach a few centimetres relative to the National Spatial Reference System, both horizontally and vertically.

This approach to positioning in RTK is radically improving productivity and the quality of the survey. Deleting the installation of a reference receiver, the professional will save time and money for the purchase of a second receiver. With a permanent GPS/GNSS network, control data is always guaranteed and it is possible to reduce the propagation of errors resulting from improper placement of the reference receiver. The receiver will initialise faster and the quality of all data will be monitored before one can get them. Such a system application can find its way in various applications like survey works, monitoring, construction control, asset management, cadaster, navigation, etc. The solution enables customers to increase productivity and reduce costs — there is no need to use a separate base station.