If you are new to GPS surveying, you may not know how to get accurate measurements every time.
This technique combines measurements from a fixed base station with those from surrounding virtual reference stations to achieve centimeter-level accuracy. It is a powerful tool for many applications, including land and hydrographic surveys, air navigation, machine control, precision farming, and more.
We’ve created this article to help you understand how RTK GPS systems work and how to use them effectively.
Set the Base Stations
A base station can be a fixed location or a portable device with a wireless connection. It typically uses a UHF, VHF, or spread spectrum-frequency hopping radio to communicate with mobile receivers.
Depending on the requirements of your project, you may opt for a wireless station that is available to the public or one that you can create yourself. Either way, your base station needs to be in a position that is near your work area.
The transmitter at the base station operates on a frequency range of 400-475 MHz and is typically in the UHF or VHF band. It is the same range that many emergency voice communications operate in. So, if you’re using RTK in a busy or noisy area, ensure your base station transmits on a lower frequency or in a different channel.
You can set up a base station and a rover with a small GPS antenna if you’re in a remote area. It can help reduce obstructions that might affect the satellite signals and increase the accuracy of your GPS position. Check this link to learn more.
Set Up the Rovers
RTK surveying is best suited for projects where many unknown points need to be determined and when coordinates are required in real-time. It’s also ideal for surveys where built-up areas are difficult to avoid.
It’s not recommended to use RTK in marine areas, lands with obstructed terrain, or when construction disrupts communication. The GPS accuracy will decrease as the distance between the base station and the rovers increases, so it’s best to limit this to 20-30 kilometers for most projects.
The rover receives the correction signal from the base station in real-time via radio and uses this to improve its own computed position from the GNSS constellations. The rover then moves from point to point, stopping momentarily at each new position.
If the rover cannot get a direct connection with the base station, it can obtain data from a radio beacon broadcast by a nearby radio antenna. These radio beacons are available for free in many regions.
You must set the rover up with an RTK base to use it. It involves setting up the receiver information interface, similar to the base station’s, and establishing a Hi-Target connection.
Check the Positions
RTK (Real-Time Kinematic) GPS Systems allow you to get accurate measurements every time. They also help you save money and time by reducing the number of satellites needed to determine position accuracy.
To ensure the accuracy of your measurements, it is important to set up your base stations and rover equipment correctly. It requires a bit of planning and experimenting.
Once your base station antenna is properly located and the rover is connected, you can begin checking your positions. This process will vary depending on the type of base station you use and the terrain around your site.
For example, a base station antenna should be located at least 5 meters above ground on a known point, such as a radio tower or building corner, for effective operation. The RTK system will not work if the antenna is not pointed in a direct line of sight to the satellites.
Another important aspect of setting up a base station is to check for interference from other radio signals and electrical equipment in your area. It can cause problems with the signal lock or offset.
A high-quality GNSS antenna is essential for RTK accuracy. It must be able to withstand harsh weather and other outdoor conditions. It should also capture multiple signals from the satellites in a single transmission. A high-grade GNSS receiver is also essential to your RTK surveying equipment.
Take the Measurements
The first step in taking measurements with an RTK GPS is to set up the base station and one or more mobile receivers in the field. These receivers are located near a surveyed point and can receive radio corrections from the base station.
For RTK surveying to work properly, you must have a line of sight between the base station and the surveyed point. It means you need to place the base station antenna at least 5 meters above ground on a known point. It would help if you kept it protected from the weather and other hazards such as trees and trees.
Before you buy a GPS unit, take the time to research its features and options. It can help you decide whether it is the right unit for you and your needs.
You can also save money by purchasing a used unit, as these typically come with two years of warranty. You should always investigate the details of a warranty before purchasing to ensure that you are protected against any problems that could arise with your equipment.