RTK (Real Time Kinematic) technology is a crucial part of most strip-till operations. In fact, 91% of strip-tillers surveyed in the 2023 Strip-Till Benchmark Study are using RTK guidance with strip-till. But RTK remains one of the most misunderstood terms in agriculture, according to DigiFarm RTK expert Steve Riddle.

Riddle, a 35-year veteran in application equipment and precision ag, helped strip-tillers develop a clearer understanding of the various types of RTK technology during a recent Strip-Till Farmer webinar. 

"No matter the provider or system, we all have the same rules that affect the RTK accuracy," Riddle says. "For every 10 miles from where you are in relation to the nearest base station, you lose 1 inch of repeatable horizontal accuracy. Vertical control accuracy is more difficult, but the rule of thumb is double your horizontal error to determine your vertical accuracy level." 

Riddle breaks down the various types of RTK technology below.

Portable Radio Base RTK

"In this scenario, you're putting up a portable base in the field less than a mile from where you're working," he says. "This is good if you just need to knock something out in a day. But if you want to strip-till with this, come back later and plant, then the portable base has to be in exactly the same spot as it was when you made strips."

- Trees, hills or changing terrain can disrupt signal and make it not receivable
- Quick survey process with adjustable parameters for accuracy needs
- Remote power source needed
- Time consuming to set up and move
- Difficult to use and be accurate with repeat applications
- Does not provide short base lines for accuracy

Radio RTK Mounted on Base Tower or Grain Leg

- Survey process: 24 hours or less
- Most likely to have line shift if switching to a VBN (Virtual Base Network) or VRS (Virtual Reference Station)
- Remote power source needed
- Need to enter base ID and manage which base is used with each field
- Most likely to be affected by extreme weather or lightning
- If one base is down, others nearby may not be able to be used with line-of-sight restrictions

Single Base Cellular RTK

- Most states have a CORS (Constant Operating Reference Station) that is used with this, but not all states have one
- Survey process: 24 hours or less
- Most bases cover RTK at a 30-mile radius
- May need to change base ID information if traveling far
- If base goes down, the nearest base may be 50+ miles away, with degraded accuracy
- Downtime can be lengthy if a state's CORS is doing updates or encountering server problems
- Many are limited to brands of GPS they support

VBN/VRS Cellular RTK

- Similarities to single base cellular RTK
- Not line of sight restricted
- Not tower or grain leg mounted. Typically 2 story height with secure mounting and clear view of sky
- GPS at base via receiver/router through internet connection communicates with providers' server
- Cellular signal is sent from providers' servers in form of cellular data packet, same as text messages
- Each uses physical base stations to create a VBN
- Physical base stations are used to triangulate the rover's position when a session is started
- The rover then sees the virtual base as the nearest base
- A cluster of 5 or more base stations are needed to accurately create a virtual base in addition to the providers' capability 

Riddle dives deeper into these different types of RTK technology in the webinar replay below, and explains why RTK does not always result in sub-inch repeatability. He also breaks down the differences of Datums, NAD83 and JDITRF, and how they might affect line shifts when sharing guidance lines between various brands of GPS.