Using satellite imagery to check centre pivot performance New

Date: 12-Nov-2026

Recurring crop patterns can help growers identify which part of a pivot to inspect. Field measurements show whether it is applying water as intended.

A centre pivot can deliver close to its usual total flow while some areas receive too little or too much water. A blocked nozzle or an incorrect pressure regulator may make little difference to the flow meter reading for the whole machine. Over several passes, though, uneven watering can leave a band of crop growth that follows the sprinkler’s path.

Why uneven watering can leave a ring

Each sprinkler travels at a fixed distance from the pivot point, so a persistent fault can show up as a ring or arc. Sprinklers farther out sweep more ground per revolution. That is why the sprinkler package is designed to deliver more flow per metre of pivot length towards the outside for a given application depth.

The position of a band matters as well as its width. On a full circle, a 10 m wide band centred 300 m from the pivot point covers about 1.9 ha, three times the area of the same width at 100 m. Because sprinkler patterns overlap, the radius points to a section to inspect rather than a particular nozzle.

What the satellite sees

One common measure is the normalised difference vegetation index (NDVI), which uses the contrast between reflected red and near-infrared light to indicate green canopy cover and vigour. Differences in the index can also reflect soil variability, drainage, nutrition or disease. Wheel tracks and planned changes in irrigation rate can leave circular patterns too.

A band that reappears at the same radius on clear images is worth investigating. Consider the crop stage and recent rainfall: a crop may show little response to uneven irrigation after rain, and a narrow band can be obscured if the satellite pixels are too coarse. A clear image with no visible ring does not rule out a fault.

What the research shows

In a Soil Wealth ICP case study near Cowra in NSW, satellite imagery showed arcs of weaker potato growth under two spans about two months before harvest. The project team linked those arcs to sprinklers delivering too little water. A separate patch in the same image was thought to reflect soil disturbance from land levelling.

In a 2024 study of 36 centre pivots, satellite estimates tended to overstate uniformity compared with catch-can measurements. A 2025 study applied machine learning to distinguish patterns consistent with sprinkler and pressure problems from patterns such as partial crop cover. Both studies investigated the broader method; neither evaluated PivotScan.

How PivotScan uses repeated images

One Australian example is PivotScan, offered by Nelson Irrigation Australia in partnership with DataFarming. Nelson describes using automated image analysis to flag bands of different crop vigour at a consistent distance from the pivot point. A seasonal map combines the detections to show where patterns recur.

A value of 75% on that map means a pattern was flagged in three quarters of the images analysed for that season. It does not quantify any water deficit or show how long a fault was present.

How to check a flagged band in the paddock

Locate the section to inspect. Use the radius of the band and the sprinkler chart to identify the relevant span and neighbouring outlets. Check nozzle sizes and positions, look for wear or blockages, and verify that the regulators match the design.

Measure what is being applied. Compare operating flow and pressure with the design values, including pressure near the far end. A catch-can test along radial lines measures the depth applied during a pass. A whole-pivot uniformity calculation weights the readings to account for the larger area covered by the outer spans.

Check the effect of the repair. Repeat the measurements under comparable conditions and record the work done. Restoring flow to a dry band can improve uniformity without reducing total water use. To assess savings, compare metered volumes and take account of changes in rainfall, crop water demand and irrigation scheduling.

Nelson Irrigation Australia, an Irrigation Futures sponsor, provided information on PivotScan.