To further validate the proposed upscaling approach using independent data, such as field campaign measurements or airborne remote sensing data, several steps can be taken:
Field Campaign Measurements: Conducting field campaigns where soil moisture measurements are collected at various locations within the study area and potentially in similar agricultural regions. These measurements can serve as ground truth data to compare against the upscaled soil moisture estimates. By comparing the upscaled values with the field campaign data, the accuracy and reliability of the upscaling approach can be assessed.
Airborne Remote Sensing Data: Utilizing airborne remote sensing platforms equipped with sensors capable of capturing high-resolution soil moisture data. By collecting airborne remote sensing data concurrently with in-situ measurements, a direct comparison can be made between the upscaled values and the airborne data. This comparison can help evaluate the consistency and accuracy of the upscaling approach at different spatial scales.
Integration of Multiple Data Sources: Combining field campaign measurements, airborne remote sensing data, and existing in-situ measurements can provide a comprehensive validation framework. By integrating data from diverse sources, the upscaling approach can be thoroughly evaluated under varying environmental conditions and landscape characteristics.
Statistical Analysis: Employing statistical methods such as regression analysis, correlation coefficients, and error metrics (e.g., RMSE, bias) to quantitatively compare the upscaled soil moisture estimates with the independent data sources. This analysis can provide insights into the agreement between the upscaled values and the ground truth measurements.
Spatial and Temporal Consistency: Ensuring that the upscaled soil moisture estimates exhibit spatial and temporal consistency with the independent data sources. Any discrepancies or outliers should be carefully examined to identify potential areas of improvement in the upscaling methodology.