Soil Moisture Mapping of Golf Greens Using a Vehicle-Mounted L-Band Polarimeter

Soil moisture on golf greens affects playing conditions, turf health, and irrigation scheduling, but visual inspection is subjective and point probes undersample how moisture varies within a single green. We describe a passive L-band (1.4 GHz) radiometer mounted on a greensmower that maps soil moisture during routine mowing, producing hundreds of measurements per green on each pass. The instrument is a digital polarimeter: it measures all four Stokes parameters, and the polarisation information can be used to separate radio frequency interference from the thermal emission of the soil. An automated per-green calibration maps the brightness temperature distribution accumulated over many mowing sessions onto the expected soil moisture range of each green, set by calibration anchors at the dry and wet ends. This converts brightness temperature to volumetric water content (VWC) without extra field calibration. We evaluated the retrieval on five putting greens at Waterford Valley Golf Club, Melbourne, Australia, against a handheld FieldScout TDR probe (mean R2 = 0.42, mean bias +3.1% VWC). The within-green spatial patterns repeated across the eight-week observation period, resolving the wet and dry zones of each green. Once the reference probe’s own error was removed, the microwave random error was between 6 and 8% VWC, estimated from a single field day. We tested the polarimetric interference rejection across the whole course. The system’s strength is dense, repeatable mapping of relative soil moisture structure.