GPS Auto-Steer Swath Control (2D)

Guidance & Equipment

Steering guidance

Implement width 8.0 m

Travel speed 8.0 km/h

Field width 54 m

Map zoom 1.0×

Coverage — Live

Overlap area

0.0%

Skipped area

100.0%

Excess input (waste)

0.0%

Current cross-track error

0.00 m

How it works

A tractor pulls an implement of width W across the field in parallel passes spaced W apart. If the driver — human or auto-steer — held a perfectly straight line, every pass would exactly abut the next with zero gap and zero overlap. In reality the vehicle wanders sideways off its planned line by a cross-track error (CTE) that depends on the guidance system:

CTE random walk (per row j along a pass):
  e[j] = 0.85·e[j-1] + N(0, σ_eff)     (mean-reverting: driver/auto-steer keeps correcting back)

σ_eff = σ_base(guidance) · (1 + max(0, v−6)·0.08)   v = travel speed, km/h

σ_base:  manual ≈ 0.25 m · WAAS GPS ≈ 0.08 m · RTK GPS ≈ 0.02 m

Each field cell is rasterised and counted for how many pass-swaths actually cover it:

covered(cell, pass i) = |x_cell − (center_i + e_i[row])| ≤ W/2
count(cell) = Σ_i covered(cell, i)

Skip %     = cells with count = 0   ÷ total cells
Overlap %  = cells with count ≥ 2   ÷ total cells
Waste %    = Σ max(count−1, 0)      ÷ total cells   (extra chemical/seed dosed on double-covered ground)

Guidance sets σ_base — this is the single biggest lever: RTK auto-steer holds the line roughly 10× tighter than a human driver.
Implement width — a wider boom needs fewer passes, but the same CTE eats a larger fraction of each swath, so overlap/skip % actually worsens for very wide gear on rough ground.
Travel speed — faster driving leaves less time to correct drift, inflating σ_eff for every guidance mode.
Field width — sets how many passes the field needs; more passes means more edges where overlap and skips accumulate.

Real-world relevance: this is exactly why RTK auto-steer is standard on modern precision-ag equipment — cutting overlap from ~8–12% (manual) to under 1% pays for the hardware in fertilizer and seed savings alone within a season or two.

The drift trace panel below the field map plots this same e[j] cross-track-error signal live as the tractor advances, with the implement's half-width band shaded — the trace crossing outside the band is exactly the moment a strip goes from "still inside this swath" to "skipped, to be picked up — or missed — by the next pass".

Pass 1 / 1

drag to pan · scroll to zoom

Unapplied / skip Correctly applied Overlap (double dose)

GPS Auto-Steer Swath Control Simulator (2D Field Map)