Buyers guide: Retrofit entry-level auto-steer systems

Free satellite signals and plenty of competition between manufacturers mean simple agricultural GPS guidance systems are more affordable than ever.

For less than £1,000, firms such as Patchwork and Agricision can provide a tablet-based GPS lightbar that will help guide operators in arrow-straight parallel lines with a pass-to-pass accuracy of between 20 and 30cm.

That’s precise enough for spinning fertiliser on grassland or spraying off stubble fields, but when it comes to crop establishment, they’re a little too woolly to deliver tidy results.

Unsurprisingly, plenty of people have had a stab at using them for drilling, either in conjunction with markers or by upgrading to a system with a more accurate correction signal and focussing on the flashing lights like a hawk.

But while this can work well, it’s far from relaxing. Getting the proper benefit of an accurate GPS system means investing in some sort of automated steering device.

When teamed with a receiver that’s capable of picking up a correction signal with sub-10cm accuracy, the two will work together, providing constant, rapid adjustments that keep the tractor and implement on the correct path.

This technology isn’t available to many of the smaller players, so it generally means dealing with the key GPS providers such as Trimble, Topcon, Ag Leader and Raven. However, Dutch/Ukranian firm eFarmer does offer a DIY setup.

See also: 6 budget GPS guidance system options for farmers


In all cases, there’s a significant jump in price from the most basic offerings, and buyers are introduced to a new world of unlock fees and annual subscriptions for correction signals.

These can seem hard to swallow, but the reduction in input costs from fewer overlaps generally results in quick payback times.

Most manufactures in this sector operate a modular setup so, once the initial investment has been made, it’s generally less expensive to add the kit onto other machines and access features such as variable-rate application and automatic sprayer section control.

Many people will also purchase a few extra components so that the system can be transferred from the drilling tractor to the sprayer and then to the combine.

GPS signals at a glance

Basic GPS – no differential correction means accuracy is 2-5m. Examples include GPS, Glonass and Galileo.

Differential GPS – free correction signals provided by Egnos and WAAS, with 30cm pass-to-pass accuracy (as used by most lightbar guidance systems).

High-performance differential GPS – more accurate subscription-based correction signals, provided by the likes of Omnistar, offering pass-to-pass accuracy of 15 to 2.5cm, depending on the amount precision a buyer needs.

RTK – the most accurate and consistent correction signal with repeatable accuracy of 2.5cm or less. It requires a base station or a subscription to access others.

Most manufacturers have their own networks and there are a number of independent options. The signal can be sent over short distances via radio signal and considerably further when using mobile internet.

For the purposes of this article, we’re concentrating on the large number of second-hand and new tractors in the UK that didn’t come out of the factory auto-steer ready.

This means they don’t have the necessary smart steering valves that aftermarket GPS units can plug into.

Although these valves can be retrofitted, the fee can run to many thousands of pounds, so in most cases it makes more sense to opt for a motorised system that attaches to the steering column.

Early versions of these were a little crude, but current models can deliver accuracy approaching that of integrated systems.

Below, we take a look at four setups from the main players in the UK, plus eFarmer’s FieldBee DIY option that can be ordered from the Netherlands.

Discounts are likely to be available on some of the prices quoted and many firms will offer to buy back older displays, which helps lower costs.

Trimble EZ Pilot


Trimble’s agricultural GPS equipment is sold by Soil Essentials in Scotland and Vantage England and Wales south of the border.

Vantage England and Wales is a subsidiary of Cambridgeshire-based precision farming firm AS Communications and was formed purely for the Trimble side of the business. The Irish market is served by Vantage Ireland.

Trimble offers four displays that are capable of receiving correction signals accurate enough for drilling. Prices for these start at £1,850 and go up to £4,595, but buyers will also need to pay an unlock/licence fee before the display can access more accurate signals.

So realistically, the fees for displays capable of drilling accurately range from £4,534 to £6,946.

According to Vantage, the GFX 750 is one of the most popular for this sort of setup as it has a large display, runs the newer-type Precision IQ software and can be upgraded in the future. It costs £6,141, including a licence for the firm’s Centrepoint RTX signal.

The first step up from the free Egnos signal is Trimble’s Rangepoint RTX that offers sub 15cm accuracy.

Apparently, some customers are able to drill successfully with it, but the Centrepoint RTX with sub-2.5cm pass-to-pass accuracy is the better bet.

This comes in ‘standard’ and ‘fast’ versions, with the latter offering a quicker convergence time for more precise work and year-on-year repeatability.

The next step up is RTK, which has an instant convergence time and no satellite drift, making it well suited to controlled traffic farming systems that confine vehicles to the same lines year after year.

The mobile version requires an additional GSM modem and has a £750/year subscription fee. Radio versions work over shorter distances and fees are at the discretion of the individual or firm that owns the mast.

Steering system

There are two steering systems on offer from Trimble, the simplest of which is the friction-drive EZ-Steer unit that’s been around for years. It’s basically a motor with a foam rubber wheel on the end that engages with the steering wheel. 

It Is capable of driving accurately enough for drilling duties, but as it is still relatively expensive, many buyers go for the EZ-Pilot version that mounts directly to the steering column in place of the original wheel.

The EZ-Steer costs £2,500 with a GFX 750 display and the EZ-Pilot with Pro operating software is £3,396.

Guideline prices
System price: 
£13,358 – Including GFX 750 display with relevant licences, auto-steer system, one-year Centerpoint Fast subscription and installation (based on a Massey Ferguson 7618)

Optional extras: Transfer kit allowing system to be moved to another tractor – £1,361 (based on Massy Ferguson 7620)

Ongoing subscriptions: Centerpoint RTX fast correction signal – £650/year

Compass GPS display

Ag Leader

Ag Leader products are sold in the UK via Cumbrian dealer Precise Solutions, headed by Derek Johnson.

There are two displays on offer, both of which are capable of RTK guidance.

The Compass is the entry-level model with a relatively small screen and limited functions, while the large, tablet-like In Command brings a few more features, such as a split-screen view that allows simultaneous monitoring of Isobus implements.

Both units have a field finder that automatically selects the field from a list when creating a new job, as well as the ability to record field sizes and boundaries.

Prices for the Compass unit start at £1,963 (guidance only) and with the hardware for RTK it jumps up to £7,883. Upgrading to the In Command display costs an extra £1,200.

The firm’s Terrastar-C Pro signal offers 2.5cm to 5cm pass-to-pass accuracy, meaning it is accurate enough for drilling. However, according to Precise Solutions, the relatively small jump in price to its RTK setup tempts many buyers to upgrade.

It also removes most of the worries of lost signal and time spent waiting to the receiver to acquire it. Buyers can connect to their own compatible base station or access Precise Solutions’ RTK network, which covers the UK and Ireland.

Annual subscriptions for this are £650, which includes data sim cards and remote support for the steering system. Those with In Command displays also get satellite imagery over the field.

Tractor steering wheel

Steering system
For tractors that aren’t auto-steer ready, Ag Leader offers its Ontrac 3 bolt-on steering unit. It has a ring gear that fixes under the steering wheel and there’s a clip-on drive unit to do the steering.

This setup means the original steering wheel can be retained and it makes swapping it to another vehicle pretty simple. 

Guideline prices
System price: £12,990 – Including Compass display with relevant licences, auto-steer system, one-year Ag Leader RTK subscription and installation (based on a Massey Ferguson 7618)

Optional extras: Transfer kit allowing system to be moved to another tractor – £1,243 (based on Massy Ferguson 7620)

Ongoing subscriptions: Ag Leader mobile RTK signal – £650/year or a subscription to another compatible network.

Tractor cab


Raven GPS systems are available in the UK through Dempsey Precision, which is run by Vince Dempsey.

There are two auto-steer compatible displays from Raven – the 7in CR7 and the 12.1in CR12. Both work with the firm’s high-accuracy GS correction signal and with the relevant unlock codes and antenna they cost £1,680 and £6,410 respectively.

The CR12 includes more features than the CR7, but the smaller screen can have a number of upgrades, including unlocking the variable rate controller at a cost of £780. Both screens can be made Isobus compatible for a one-off fee of £820.

Raven’s GS correction signal offers pass-to-pass accuracy of 4cm or less, making it well suited to most drilling jobs.

An annual subscription is £1,230, but there’s the option of having it for three months at a cost of £495. In this instance, the system will still work on Egnos with 30cm accuracy for the rest of the year.

For those that want year-on-year repeatable accuracy, it can be upgraded to RTK.

Steering system
Raven offers a bolt-on steering wheel kit, but in most cases Dempsey Precision recommends fitting non-auto-steer-ready tractors with an integrated hydraulic steering valve.

This operates like a factory-fitted system and is actually slightly cheaper than the steering motor kit.

The valve and its ECU hydraulic driver unit costs £1,850, installation is about £900 and there’s roughly £250-worth of pipework, depending on where the valve is situated. Those that are mechanically minded can save a few quid by fitting the valve themselves.

Opting for an MD electric steering wheel system is £200 more, but the benefit is that it’s simpler and cheaper to swap between machines. Basic transfer kits start at about £530.

Guideline prices
System price:
£10,110 – Including CR7 display with retrofitted hydraulic auto-steer system, one-year GS signal subscription and installation (based on a Massey Ferguson 7618)

Optional extras: Hydraulic transfer kit, allowing the system to be moved to another tractor – £5,250 (based on Massy Ferguson 7620) including pipes and installation.

Ongoing subscriptions
Raven GS correction signal – £495 for three months, £1,230 for 12 months, £3,360 for three years, or £5,240 for five years.

Option to hire
For those that don’t want the capital outlay of a full auto-steer system, Dempsey Precision offers a couple of hire options, both of which it supplies with RTK correction signal.

For tractors that aren’t auto-steer ready, the owner needs to commit to have the system for a minimum of three years. Dempsey Precision will then install a hydraulic steering valve and charge a £1,500 subscription for the spring season and £1,500 for the autumn.

Those with an auto-steer-ready tractor only need to commit to six months at a time, at a cost of £1,500.

Tractor cab


Cambridgeshire-based guidance specialist LH Agro distributes aftermarket Topcon Agriculture equipment in Great Britain. 

Topcon display

Topcon offers two displays that are capable of auto-steer guidance accurate enough for crop establishment. The key difference between the two is screen size, with the X25 measuring 8.4in and X35 12.1in.

However, the X35 also has some extra features, mainly the inclusion of Task Control (section and rate control) for Isobus implements as standard. The X25 costs £2,665 and the X35 is £4,670.

Topcon’s AGI-4 GPS receiver is separate to the display and features a built-in steering controller. This is capable of controlling most new auto-steer-ready vehicles without any additional hardware.

The AGI-4 also houses the licence for the relevant correction signal. Configured for RTK, it costs £9,675.

Topcon’s medium-grade Topnet Global D correction signal offers 8-10cm accuracy, meaning it’s just about precise enough for drilling.

However, its activation fee is close to that of an RTK setup, so in most cases it’s worth upgrading and getting 2.5cm accuracy. 

The firm has a network of base stations that covers most of the UK and these can communicate with the tractor via radio signal or the mobile phone network.

An annual RTK subscription costs £650 and, if required, this includes data and a roaming mobile sim card that works across all networks.

Steering system
The AES-35 electric steering wheel system is the firm’s simple option for converting tractors that aren’t auto-steer ready, and it slots onto the steering column in place of the original wheel.

The basic unit costs about £3,500, with some slight variation on price depending on the vehicle.

Various adapter bosses are available to fit most makes of tractor, sprayer and combine, and additional kits can be purchased so that it’s quick to swap between machines. 

Guideline prices

System price: £12,975 – Including X25 display, AGI-4 RTK receiver with NTRIP modem and UHF radio, auto-steer system, one-year RTK subscription and installation (based on a Massey Ferguson 7618)

Optional extras: Transfer kit allowing system to be moved to another tractor – £595 (based on Massey Ferguson 7620)

Ongoing subscriptions: RTK signal (radio or mobile phone) – £650/year

Tractor cab

eFarmer Fieldbee

Dutch and Ukranian precision agriculture firm eFarmer is one of the few smaller GPS providers than can offer a bolt-on kit capable of auto-steering a tractor to RTK accuracy.

It was formed in 2014 and now has a number of dealers across Europe selling its Fieldbee guidance systems. It is yet to have a dealer in the UK, although it is looking to appoint one.

In the meantime, it is possible to order the systems directly from the firm’s headquarters in the Netherlands and get support from there.

This does means buyers will need to fit the system themselves or enlist the help of an agricultural engineer, so there’s no easy option of getting the manufacturer to come out and sort any problems.

Like some of the other smaller guidance system providers, Fieldbee runs all of its guidance through an Android app that can be installed on any compatible tablet or smartphone.

The basic version is free to download, but the full-spec option required for auto-steer is subject to a €119 (£104)/year subscription.

The buyer will need to provide their own tablet, but Android units can be picked up fairly cheaply.

FieldBee base station

Unlike most of the large GPS providers, Fieldbee doesn’t use medium-accuracy correction signals that command a subscription fee.

Instead, it uses free signals like Egnos for lower accuracy tasks and RTK where greater precision is required. The firm’s RTK setup is a two-tiered affair, starting with an L1 receiver that only gives accurate results in flat fields without obstacles.

Those are few and far between in the UK, so its recently introduced L2 receiver is the best bet where drilling accuracy is required – this costs €1,299 (£1,137).

Those that can access a local NTRIPP RTK base station (either owned by a neighbouring farmer or a network) can simply pay to access the signal.

But where there’s no option of this, or the buyer would like to avoid subscription fees, there’s the option of adding an L2 RTK base station that can be installed at the farm.

This can broadcast its signal over 2.5km via radio signal or 20km via mobile internet and costs €1,599 (£1,399). Pass-to-pass accuracy is said to be 1cm.

Steering system
Fieldbee’s steering system is the same bolt-on arrangement as used by a number of other firms, and is built by Agjunction (formerly Novariant).

This is by far the most expensive part of the setup and costs €5,699 (£4,986), including the fee to unlock it so that it works with RTK.

It clamps under the existing steering wheel and can be easily removed and moved to another vehicle.

Guideline prices
System price:
€7,134 (£6,242) – Including receiver, auto-steer system and one-year subscription to premium software (this is a universal kit to suit most tractor models)

Optional extras: Fieldbee L2 base station to give subscription-free RTK correction signal – €1,599 (1,399).

Ongoing subscriptions: €119 (£104) for premium subscription to Fieldbee app, plus fees to access local NTRIP RTK signal if no base station is purchased.


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