GPS and RTK
GPS and RTK
How Sub-Inch Accuracy Makes it to Your Field…
In order to understand RTK, it helps to have a small understanding of GPS (Global Positioning System). GPS can be quite complicated- thinking in 4-D space and grasping quantum mechanics is fairly difficult for most. Below you will find some helpful links if you’re interested in brushing up on your GPS knowledge.
Very simple explanation: Physics.Org
The video below goes into a bit more detail:
Although GPS can deliver a specific location fairly accurately, as the video explains, it can have an error range of from about 3M up to 15M. There are a variety of factors contributing to these errors such as frequency interference from satellite clocks, orbit errors, ionospheric and tropospheric delays, receiver noise or multipath. In order to correct these errors, other sources are needed to do so. This is where RTK (Real Time Kinematics) comes in, as it is one of the most precise methods used for error correction.
RTK uses permanent fixed base stations, set up within a radius, which communicate between GPS satellites and a central processing station. With RTK, the base stations remain at a fixed point, therefore their latitude, longitude and height data is recorded and set. This fixed information is used to decipher inconsistencies received from satellite transmissions. If one or more satellites is sending information which appears incorrect, the base stations recognize an error. When the base stations send this information to the central processing station, it uses algorithms to process the error information, corrects the errors, and forwards the corrections back to the base station. The base station then communicates the corrections to the rover, so it is able to account for the incorrect GPS information it received from the satellites.
CELLULAR RTK vs. BASE STATION RTK
Hanlon’s RTK network is a cellular network meaning it uses cellular data to transmit information as opposed to radio frequencies (used by base station RTK). Because of this, a line of sight is not necessary between the base stations and the rover. This obviously has many advantages for the end user. With cellular RTK, base stations do not need to be located on a users property- meaning no moving stations around or entering codes to pick up a signal. The rover is simply equipped with a SIM card to send and receive information, which also eliminates the need to lug around heavy radio equipment in the field. The SIM card in the rover seamlessly detects the best station (located up to 70km away) and immediately begins transmitting its location while receiving its necessary location corrections.
Another advantage to cellular RTK is repeatability. Because the base stations are permanent, previous lines can stored on your terminal and be utilized for days, months or years to come. With cellular RTK there is no limited communication range, no need for licensing (some radios require that) and there is no need to worry about radio interference.
What Separates Hanlon’s RTK Network?
- Serviced Internally- our dedicated technicians are available when you need them.
- No need to worry about extra data charges or other costs- our flat yearly rate of $1,500 covers it all
- Dependable- our network has been up and running for 5 years
- Maintenance free- we service the base stations and ensure the network is operating properly
- Installs on any equipment- works with all major GPS systems
Want to know more? Hanlon Ag Centre RTK Network
*This article is from Hanlon Ag Centre’s March 2019 Newsletter.
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