Tracking spot spraying on foot

Why walking needs different rules

A tractor tracker throws away positions that barely moved. It has to: a machine sitting idle still produces a stream of GPS fixes that wander about with the noise, and recording all of them would paint a growing blob of coverage where nothing is being worked.

Apply that rule to a person with a knapsack and you lose the job. Someone spot spraying stands still, because that is what spot spraying is. They stop at a plant, treat it, move three steps, stop again. The fixes that a tractor tracker discards as noise are the work.

So AgriPilot switches rules when the equipment you have selected is a handheld sprayer. It stops discarding stationary fixes and records while you stand. It keeps the check that throws away genuinely bad positions, because a fix that is thirty metres out is still wrong. And it adds a speed ceiling: above about 14 km/h you are driving, not walking, so it stops recording rather than painting a coverage trail down the track on the way to the next field.

How the area is counted

Behind a boom, worked area is distance multiplied by width, a running total where crossing the same strip twice counts twice. On foot that answer would be useless. If you stand over one thistle for forty seconds, a running total keeps adding area for as long as you stand there, and you finish the morning with a number several times the size of the ground you treated.

Handheld coverage is counted differently. The ground is treated as a grid of half-metre squares, and each square is either sprayed or it is not. Standing in one place fills the squares within your spray radius once; standing there longer fills nothing new. Walking a circle back over your own steps adds nothing where you have already been. The area you get is the area you actually covered, and it cannot double-count.

Set the spray width for the handheld equipment honestly, meaning the width of the wetted band from your nozzle at the pressure and height you actually use, not the maximum the nozzle is rated for. Everything above depends on that figure.

What it looks like in use

The map zooms in closer than it does for tractor work, because the detail that matters is a few metres across rather than a few hundred. The machine icon is replaced with a dot showing where you are, with a ring around it sized to the current GPS accuracy. That is a straightforward way to see whether the fix is good enough to trust before you start counting on the coverage.

The on-screen figures change to suit: sprayed area, distance walked, elapsed time and current accuracy. Markers are useful here too. Drop one where you find a patch that needs a follow-up, and the app will tell you the distance and direction back to the nearest one you have not dealt with.

The limits worth knowing

Phone GNSS accuracy is three to five metres in the open, and that does not improve because you are walking. Half-metre grid squares are finer than the position feeding them, so treat handheld coverage as a reliable record of the area you worked and a rough record of exactly which square metre. Under a tree canopy, where a lot of weed work happens, expect it to be worse, and watch the accuracy ring.

As with tractor work, this is a record of where you walked, not a chemical application record. Product, rate, batch and weather belong in something built for compliance paperwork, such as our separate app Spraybook. The walked track exports as GPX if you want to attach it to that record.

One practical note: a phone recording GPS with the screen on for a morning will flatten a battery. Carry a power bank if the job is a long one.