Ever wonder what's going on in the background as your guidance system adjusts to keep you in line?
The guidance controller mounted on the top of your cab, commonly referred to as a GNSS receiver, is the heart (and sometimes brain!) of the system. Depending upon the type of receiver you have installed, it will utilize a number of satellite constellations to pinpoint your exact location using position, velocity and time measurements.
Your correction service, whether free or subscription-based, talks to the receiver and tells the system which way the tractor should go to remain on the guidance line. High accuracy corrections are typically subscription-based and are used to overcome signal errors from satellite positioning to make sure you stay on-line, all the time. The information collected through the corrections then triggers your auto guidance system to adjust the wheels accordingly.
With so many moving pieces, you can easily see why each guidance component is critical to the performance of the system.
Why Corrections Matter
Do you deal with dropped and unreliable correction signals? It's important to take a look at the type of corrections you're using and what your receiver is capable of.
You get what you pay for with free correction services. While they are often great for broadacre crop work, they also suffer from outages that may not be immediately apparent, resulting in skips and overlaps in coverage. There is a wide array of correction services available to you, with their main differences based on their performance on the ground:
SBAS: Satellite-Based Augmentation System
Meter-level accuracy
Available on a continental level delivered via satellite
Accurate only if within the coverage network
May be blocked by trees, buildings and other obstructions
Does not require a subscription
RTK: Real Time Kinematic
Centimeter-level accuracy within range of a base station
Delivered via radio or cellular connection
Base station set up required by user
Modem required for cellular connection
Accuracy is lost as you move further away from the base station
Cellular connections can impact operation
VRS: Virtual Reference Station
Centimeter-level accuracy
Network availability based on region
No base station required; uses cellular connection and a network of stations to avoid losing accuracy based on position
Requires a VRS subscription service, modem & data plan
Greater coverage area than RTK
Cellular connections can impact operation
RTX: Real-Time eXtended
Centimeter to meter-level accuracy anywhere in the world
Available via satellite and internet; no base station/modem required, no limitations of a cellular connection
Accuracy and convergence times* dependent upon subscription level
Internet connection requires a modem and data plan
Satellite connection requires a subscription (1 per receiver)
Convergence time is longer than RTK
Which correction service is right for my farm?
The corrections you should invest in are dependent greatly on:
What level of accuracy is needed (application and crop type)
Which coverage areas you fall within
Whether cellular coverage is strong in your area
How much you are willing to spend (base station setup is an additional expense)
High accuracy subscription services may be best for working with specialty crops like potatoes, where you can’t see the crop below you. In other general use cases, SBAS may be sufficient for large row-crop farmers using it in a tillage application. Your local dealer can provide additional insight into which service is best for you.
Receiver Considerations
Remember, the type of receiver you have still matters. Chances are that older receivers will support a smaller amount of constellations** and have less processing power. Newer receivers include more up-to-date features and, in most cases, have built-in systems to overcome signal errors such as:
Antenna delays for signals at different elevations
Bounced signals that could cause positioning errors for an older receiver
Satellite inaccuracies caused by drift from their expected location
Guidance controllers like the PTx Trimble NAV-960 can track a wide range of satellites including the GPS, GLONASS, Galileo, Beidou and QZSS constellations. The steering inertial sensor and orientation engine improves vehicle positioning and line following performance. Features like the ProPoint GNSS engine overcome challenging conditions where signal can become partially obstructed by trees, buildings or other objects and improve continuity, convergence and smoothness. The receiver also has GNSS filtering algorithms from Trimble IonoGuard technology that provide optimal performance during solar events, increasing uptime even in challenging conditions.
Nothing says challenging like farming under solar panels.
Sometimes innovation looks like utilizing the same land for multiple purposes. For EDF, a photovoltaic solar panel provider just south of Paris, France, that means producing electricity and growing crops in the same space. With solar panels constructed above winter wheat, positioning errors are common, as the solar panels block the signal.
This field was serviced by a small tractor equipped with PTx Trimble’s Autopilot Motor Drive steering system and Trimble’s CenterPoint RTX Fast corrections service. During beta testing with the new NAV-960 receiver to evaluate its capabilities, users were surprised by how well it performed despite the challenging farming environment. The receiver’s ProPoint™ GNSS engine helped ensure accuracy without dropped signals. This field test also evaluated the impact that solar panels have on yield. While the results from this specific field are still yet to be determined, other sites have seen yields maintained at 93% that of conventional yields, and in some cases, positive yield gains due to solar panels providing crop protection from high temperatures. With accuracy on the ground, utilizing land for both crop and electricity production becomes an ever-appealing way to optimize a single space for increased revenue.
Uptime is your most precious resource. Don’t let an old receiver or the wrong corrections service cost you time in the field. Get accuracy that fits your operation today.
*Convergence time is the time it takes for multiple satellites in various locations surrounding the earth to calculate and fix your position.
**Constellations are a group of satellites configured in planes to orgit around the earth and provide global coverage. The GNSS constellations include GPS (US), GLONASS (Russia), Galileo (EU), Beidou (China) and QZSS (Japan).
