Optimization of CRNP Deployment Strategy and Evaluation of Radial Measurement Representativeness in a Humid Hilly Region

The representativeness and response accuracy of Cosmic-Ray Neutron Probe (CRNP) systems are significantly constrained in complex terrain environments, necessitating optimized deployment strategies. This study takes a humid hilly area in western Zhejiang, China, as a case and selects five typical slope sites across undulating terrain. Using 1 m resolution DEM, NDVI, and soil classification layers, a Monte Carlo simulation was conducted to model the radial weight distribution of the CRNP system. Results indicate that the R50 radial support radius is 128 ± 17 m, and R86 is 226 ± 31 m. Under high NDVI conditions (>0.65), the detection sensitivity decreases by 12%, and the weight center shifts toward the slope direction. A deployment scoring model based on a distributed error function was constructed, and the optimized sites reduced the root mean square error by 19.4% compared to traditional empirical selections. This study provides both a theoretical foundation and practical approach for efficient CRNP deployment in terrains with high topographic variability.