Part 2 By Michael John B. Delos Reyes
On Part 1 of this series, we introduced one of the equipment used by Surveyors in doing land surveys, the Total Station. Now, let’s take a look at another equipment used in land surveys – the GNSS and see its edge over the other equipment commonly used by surveyors and Geodetic Engineers.
The Global Navigation Satellite System (GNSS)
GNSS is a general term that encompasses all types of satellite-based positioning systems. It is a constellation of satellites that orbits the Earth and continuously transmit signals that enable the user to determine positioning, navigation, and timing services on a global or regional basis.
GPS is a type of GNSS. It is a constellation of satellites developed by the United States Department of Defense. There are 4 kinds of GNSS in the world: GPS, GLONASS, Galileo, and BeiDou. GNSS-compatible equipment can use satellites from other networks beyond the GPS system, and more satellites mean increased receiver accuracy and reliability. All GNSS receivers are compatible with GPS, but GPS receivers are not necessarily compatible with GNSS.
GPS and GNSS consist of three segments: the space segment (satellites), the control segment (ground control stations), and the user segment (GNSS or GPS receivers). Some function of the space segment is to receive and store information sent by the ground (control) station and send location information to users in real-time. The control segment is what instructs/performs necessary commands for the space segment and processes all the products for the end-users use. The user segment refers to the GNSS or GPS receiver.
Real-time kinematic positioning (RTK)
RTK is a technology used to improve the accuracy of GNSS positioning. RTK uses one stationary reference receiver called the base station, and one moving receiver called the rover.
Base stations are stationary and their location is known. It is comprised of an antenna, a radio modulator, and an amplifier. The modulator converts the correction data into a radio signal. The amplifier increases the signal’s power, which determines how far the information can travel. The base station calculates its position by utilizing the signals received from the satellites and it is compared to its known location and identifies any errors and generates a correction signal.
The rover is the GNSS Receiver whose location needs to be determined. It utilizes the correction signal from the base station to improve its own calculated position. Rovers can be moved from point to point, stopping momentarily at each new point.
Advantages of Using RTK
The primary advantage of using RTK is that a large number of positions can be established in a short amount of time. It provides centimeter-level positioning accuracy and eliminates human errors caused in traditional surveying. RTK relies on satellite, radio positioning and communication, this makes conducting survey faster. It provides GPS position in real-time and has better waypoint navigation which is required for challenging environments.
If you have projects that would require RTK surveying do not hesitate to contact our team in LPH Land Surveying Services
Allen Instruments and Supplies. (n.d.) Digital and Auto Level Equipment. Retrieved from: https://www.alleninstruments.com/geospatial-solutions/survey-engineering/digital-and-auto-levels/Iqbal, S. (8 July 2021). Digital Level Surveying – Advantages – Component – Types. Retrieved from: https://definecivil.com/digital-level-surveying/
TERRISGPS. (n.d.) GNSS/GPS Differences Explained. Retrieved from: http://www.terrisgps.com/gnss-gps-differences-explained/ Editorial Team – everythingrf. (27 July 2020) What is Real Time Kinematics. Retrieved from: https://www.everythingrf.com/community/what-is-real-time-kinematics