Site Calibration

Calibration

Another core stage of the data processing is to calibrate the signal of the CRNS. This is necessary for the sensor to adapt to site-specific soil properties, which have a pertinent impact on the neutron counts. Without it, significant biases would occur, giving a poor representation of the dynamics of the soil wetness state at a given site.

Performing site calibration typically requires taking multiple soil samples from the footprint of the sensor and then weighting and averaging the samples to find a field-scale soil moisture estimate. The most recent and widely accepted approach by Schrön et al., (2017), accounts for the variation in the footprint of the sensor for wet and dry sites, and therefore adjusts the sampling locations to account for these differences. It also considers pressure and humidity influences during the sampling period

The field-scale soil moisuture estimate, obtained from this process, can then be used to determine a theoretical neutron count for absolute dry soil conditions, typically denoted as N0. This N0 value then normalises the signal, fixing the inverse non-linear relationship between the neutron counting rate and soil moisture in place.