A novel combined optical method for objectively map soil in a near real time domain

The present study demonstrates a new concept for mapping soil, toward developing a semi-automated method to in situ classify soil. The concept is based on use of optical sensors that operate from both air and ground domains. The airborne sensor is based on imaging spectroscopy (IS) technology whereby every pixel in the image is characterized by a reflectance spectrum. The ground sensor is based on the Penetrating Optical Sensor (POS) technology whereby the optical head penetrates to the soil profile. This concept was examined over a selected field in Ashdod, a southern city in Israel. The IS data used was acquired from air scanner (AISA-ES) and POS data acquired from an ASD spectrometer over selected drill hole locations in a selected field. Five soil properties were evaluated at every drill hole depth using the Near Infra Red analysis approach (NIRS). The POS information enables obtaining an objective description of the soil profile, which was found to be more accurate than a traditional profile description using open trenches. For every selected point, six soil properties (specific surface area, organic matter, hygroscopic moisture, field moisture, carbonates, and iron oxide content) were evaluated. This information enables one to generate 5 depth layers (20-cm intervals) of the field by interpolating all points together. The 3D information provides new insight into the soils and opens up new frontiers for automatic soil mapping missions. Based on this study, further work is required in order to correlate the 3D information obtained by the IS and POS with any soil classification nomenclature system (e.g., USDA).