How Correction Services Improve Pass-to-Pass Accuracy for Precision Farming

Farming and agriculture might be some of the oldest industries, but cutting-edge technologies providing autonomy and assured positioning now optimize their yields and profits. There are many applications of Hexagon | NovAtel® products in a farmer’s field, but this article focuses explicitly on pass-to-pass accuracy with GNSS receivers and correction services 

Precision Farming and GNSS/GPS 

Precision farming in agriculture is a farming management concept that involves using GNSS positioning technologies to perform crop production applications in a variety of crop types. Applications include land preparation, planting, and measurement of crop performance in specific areas. In analyzing this data, farmers can increase crop yields by optimizing the distribution of seeds, water, fertilizer, and much more.  

Satellite positioning plays a critical role in precision agriculture. GNSS receivers installed on farming equipment can use signals from these satellites to calculate a real-time position in the field. These satellites are part of a Global Navigation Satellite System (GNSS), which includes the familiar Global Positioning System (GPS). 

From AutoSteering, variable rate seeding and spraying applications, auto section control, or soil sampling, quality GNSS positioning allows growers to plan, execute, and measure their fields accurately. NovAtel supplies high-quality technologies and services for precision farming, from receivers and antennas to corrections.  

How does GNSS improve Pass-to-Pass Accuracy? 

When working their fields, farmers move their machinery across the field in swaths or rows, eventually covering the entire area. As they drive towards one end of the field, they turn to drive back down in the other direction. The performance level, or precision (of error), between two subsequent swaths is called pass-to-pass accuracyAccuracy is critical in this process for farmers to optimize the distribution of seeds, water, and other crop inputs across their field. For some crops, it’s integral for their health to be consistently planted.

High-performance GNSS positioning technologies allow farmers to have reliable and repeatable pass-to-pass accuracy up and down their fields with minimal overlap and optimum spacing between rowsFarmers need to mitigate how much overlap occurs in order to spread their seeds and inputs evenly across the fields. Depending on the type of GNSS receiver used and its level of correction service, the error between passes can be as small as 2 centimeters (such as with TerraStar® X) or up to 15 centimeters (with TerraStar® L) with minimal deviation pass to pass, season to season, and year to year.  

Centimeter-level pass to pass accuracy is possible with a variety of GNSS correction methods.

Centimeter-level pass to pass accuracy is possible with a variety of GNSS correction methods.

Centimeter-level pass to pass accuracy is possible with a variety of GNSS correction methods. Both RTK corrections and PPP correction services can significantly improve the raw position from GNSS receivers, providing the accuracy required for these precise applications. Precise Point Positioning (PPP) corrections, such as TerraStar, are delivered over satellite and are available over very wide geographic areas or even globally, while RTK services require additional local infrastructure.  

TerraStar® PPP Correction Services and Pass-to-Pass Accuracy 

With TerraStar correction servicescorrections for GNSS satellite clocks and orbits are collected from a global network of reference stations. This data is then processed and delivered directly to NovAtel GNSS receivers over satellites.  This means that the farmer’s vehicle can be anywhere in the world and be able to receive these corrections. The TerraStar portfolio includes the services TerraStar-L, TerraStar-C PRO and TerraStar-X that enable decimeter to centimeter-level positioning accuracy for any agriculture application. 

Because TerraStar provides data through satellites already tracked by NovAtel GNSS receivers, there’s no need for additional infrastructure or equipment in the field. The system transmits corrections over three independent satellite beams, so farmers are never without correction data. Alternatively, users can also receive corrections through an internet connection. 

These PPP correction services typically require a startup period, called convergence time, to reach its full advertised accuracy. Once the solution is converged, a constant stream of corrections maintains pass-to-pass accuracy in the field. The animation below compares each level of our services, their convergence times, and pass-to-pass accuracy. 

Pass to pass accuracy and convergence times across TerraStar Services

A comparison of pass-to-pass accuracy and convergence times across TerraStar correction services.

Which PPP Correction Service is Best for Precision Farming? 

To ensure that their crop rows are closely and consistently aligned (and that their machines stay in these rows), farmers need to trust that their position will remain stable throughout their application.

TerraStar corrections are available in four service levels dependent on hardware and accuracy requirements: 

  • TerraStar-X on OEM7® receivers provides up to 2 centimeters of pass-to-pass accuracy in under 1 minute and is currently only available in the US Corn Belt region. 
  • TerraStar-C PRO on OEM7 receivers delivers up to 2 centimeters of pass-to-pass accuracy with a convergence time of 18 minutes and is available globally. 
  • TerraStarC on OEM6® receivers ensures centimeters of pass-to-pass accuracy with a convergence time of 30 minutes and is available globally. 
  • TerraStar-L on OEM6 and OEM7 receivers provides under 15 centimeters of pass-to-pass accuracy in under 5 minutes and is available globally. 

For applications requiring the highest standards of performance such as for row crop farming, TerraStar-X and TerraStar-C PRO are the most accurate options available. These two options will ensure stable, highly accurate pass-to-pass performance  offering maximum uptime and minimum start-up time without the hassle of base station infrastructure or cellular plans. Where the level of precision is not the biggest concern, TerraStar-C and TerraStar-L services are even more cost-effective and will suit many applications such as land tillage and broadacre spraying. 

Regardless of which NovAtel TerraStar correction service you choose, you can rely on us to provide assured positioning when and where you need it. 

Learn how Hexagon | NovAtel Supports Precision Farming and Agriculture Technology 

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