A simple apparatus to measure soil spectral information in the field under stable conditions

•An assembly for field surface-reflectance measurements, named SoilPRO, was developed.•The SoilPRO was tested on soil and other surfaces and compared to traditional methods.•The SoilPRO enables quality reflectance acquisition in the field under any condition.

A new assembly for measuring surface reflectance in the field was developed and built to fill the gap between laboratory and field spectral measurements of the soil surface. This device, named SoilPRO (Soil field PRObe), can be connected to any field spectrometer fiber tip and used to measure representative and undisturbed surfaces of different soil types, low grass and artificial materials. Here, the SoilPRO is presented and compared to reflectance-measurement methods that are commonly used in the laboratory (dark box configuration and the ASD® contact probe) and the field (bare fiber handheld by pistol grip and ASD contact probe). The SoilPRO's performance was evaluated by conducting continuous tests in the laboratory and outdoors with soil samples, and in the field with five different surface types as test targets. The SoilPRO's reflectance products in the field were very similar to those of commonly used methods under optimal conditions, while eliminating most of their associated errors. The device provides a new approach to spectral data acquisition in the field that enables measuring undisturbed soil surfaces while maintaining constant and stable environmental and operational conditions. The SoilPRO measures the reflectance of a representative target's footprint across the spectrometer's full range of sensitivity. The measurement is not dependent on the sun's radiation or atmospheric variations, or on operator stability or measurement geometry, and it does not disturb the surface being measured. Reflectance is an inherent property, and the assembly provides superb reflectance accuracy for the surface area in question.