How RTK Navigation Works

Regular GPS works simply: a satellite transmits a signal, the receiver catches it and calculates coordinates. The problem is that the signal passes through the atmosphere, reflects off buildings, slows down in the ionosphere. Because of this, you get an error of several metres, and sometimes tens of metres.

RTK solves the problem cleverly. The base station stands at a point whose coordinates are known to the millimetre. It also catches satellites and sees the difference between what should be and what is. This difference is the signal error. The station packs all the corrections and sends them to your receiver via the internet or radio.

Your receiver works in parallel: it catches the same satellites, receives corrections and fixes its calculations on the fly. The whole cycle takes less than a second. The main condition is you must be within 50 kilometres of the base station, otherwise the corrections lose relevance.

What the Equipment Consists Of

The base station isn't some space technology. Essentially it's a receiver with an antenna, a computer for calculations and a modem for communication. The antenna is installed on a roof or mast, where the sky is open and satellites are visible to the maximum. The station works round the clock, nobody needs to sit there.

The mobile receiver looks more compact. It's a box with an antenna that's attached to a tractor, geodetic pole or drone. Inside is a GPS/GLONASS receiver and a communication module - either mobile internet or radio at 400-470 MHz. You switch it on, wait a minute whilst the system "locks onto" the satellites - and you can work.

There are two working options. The first is your own base station, which you buy and install. The second is a subscription to a network service like SmartNet or ZAKPOS, where hundreds of stations already stand throughout Ukraine. With a network it's more convenient: you don't need to install anything, it works everywhere there's internet.

Real Accuracy Figures

When they talk about 2.5 cm accuracy, this isn't marketing. In the horizontal plane RTK gives 1-2 cm error, in height slightly worse - 3-4 cm. But this is ideal, when the sky is clear, there are many satellites (minimum 5-6), the connection is stable.

For comparison: car GPS shows your position with 5-10 metre accuracy. Differential GPS, which is used in logistics, gives 1-3 metres. RTK is a completely different level, when you can measure not blocks but centimetres.

There's a nuance with distance. If you're 10 km from the station - you'll get those same 2 cm. At 30 km the error can grow to 5 cm. At 50 km - to 10 cm. Further RTK simply stops working normally, because the atmospheric conditions above you and above the station are already too different.

Where This Is Really Used

In agriculture RTK has changed everything. A tractor with autopilot and RTK goes in even strips with 2-3 cm overlap. Previously a mechanic ploughed "by eye" with 30-40 cm overlap - that's hundreds of litres of excess fuel and tonnes of wasted fertiliser per season. With RTK one tractor driver processes 200-300 hectares per day instead of 100-150.

Surveyors now don't fiddle with theodolites and tape measures. One person with an RTK receiver on a pole sets out plot boundaries in an hour instead of a whole day. Builders transfer the project to the site - hammer in pegs where foundation blocks should stand, with accuracy to a couple of centimetres.

It's also used in cartography, when laying roads, in mining for controlling extraction volumes. Even drones for field surveying sometimes fly with RTK, so each frame has precise coordinates.

What Can Break the System

RTK doesn't like obstacles. Under dense forest, in gorges, between tall buildings the signal weakens or disappears altogether. Satellites must be visible, otherwise nothing will work. Therefore in the city centre or in mountains the accuracy drops.

The second point is communication. If the internet glitches or the radio channel is jammed with interference, corrections don't arrive and the system rolls back to ordinary GPS accuracy. Therefore they often install a backup communication channel.

After switching on RTK you need to wait 30-60 seconds, whilst the receiver "fixes" the satellites in a special mode. If the signal was interrupted for more than 10 seconds - you'll have to fix again. This isn't critical, but slightly annoying.

How Much This Costs

Your own base station - from 5000 dollars for a simple version to 15000 for a professional one with redundancy. A mobile receiver for a tractor - 2000-4000 dollars. A geodetic kit (receiver + controller + pole) - 5000-8000 dollars.

A subscription to a network RTK service works out cheaper at the start: 500-1500 hryvnias per month depending on the tariff. For a farmer with a couple of tractors this is an obvious choice. Their own station is installed by large farms or geodetic companies that work daily.

Payback is quick. A farmer saves 10-15% on fuel and fertilisers, increases yield by 5-7% through more precise sowing. Per season RTK returns its cost, and then it's pure profit.

Now compare with our prices:

Nav-Agro RTK antenna for agricultural navigation and geodesy

Promotional price: 730 €

 

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