GNSS measurement

Our experts are particularly experienced for necessary measurements of different movements during tunnels construction. Continuous monitoring during tunnel’s construction is regarded to several discrepancies, on the other side the results should satisfy very high level of realistic accuracy. Special cases are observations and evaluations of horizontal and vertical movements. Those variations are measured through pre-defined highly accurate elevation points, which are settled on stable parts of a tunnel, usually on the side or on the top of an object.

GNSS MEASUREMENT
Nowadays GNSS (Global Navigation Satellite System) are already well known all over the World. They are presented in ours everyday life, we have them in the car, in pockets and quite often we can’t imagine life without satellite navigation anymore. There are more and more equipments that receives (follows) digital signals from satellites; they can be very simple like those in our mobile phones and very complicated and expensive like those for air and sea navigation.

GNSS are well represented in the geodesy as well for a long time. In everyday surveying practice GNSS receiver became practically indispensable instrument in most geodetic offices that enables easer and faster measurement with much higher level of accuracy.

Under the term GNSS we understand all satellite navigation systems for determination ground coordinates points with the support of satellites all over the Earth’s surface. These systems are:

• American GPS (Global Positioning System)
• Russian GLONASS (GLObal’naya Navigatsionnaya Sputnikovaya Sistema)
• European Galileo and
• Chinese Compas/Bedou.

There are two basic GNSS approaches of measurements: absolute and relative. In geodesy for accurate determination of receiver’s site relative methods are most often used, because they assured up to few centimeters level of accuracy. Main characteristic of those methods are at least two receivers, one of them is located on the point with known and pre-defined coordinates and the other is on the new point. Relative GNSS methods are:

• Static survey
• Fast-static survey
• Kinematic and
• RTK (Real Time Kinematic).

With static, fast-static and kinematic method coordinates of new points are determined lately throughout appropriate calculations of observations, meanwhile with RTK method coordinates of new points are achieved in real-time. Most accurate is static approach that enables coordinates of new points with few millimeter level of accuracy. Fast-static, kinematic and RTK methods are less accurate and they assure spatial point coordinates with centimeter up to few centimeters level of accuracy.

Our company disposes with two GPS receivers Leica SR530 that enable all four methods mentioned above. All observations are lately calculated with software LEICA Geo Office Combined 7.0.1 that enables different level of data processing with combined network adjustments. Final results are spatial point coordinates within few millimeters of accuracy