An Improved Upscaling Method of In Situ Measurements With Consideration of Their Uncertainty for the Spatial Scale Match Between Satellite and In Situ Measurements.

The spatial scale mismatch between satellite and in situ-based measurements can be reduced by deploying multiple in situ sites within the coarse pixel. However, upscaling in situ measurements from the ground-support scale to the coarse pixel scale is still necessary due to their "point" measurement characteristics. The previous upscaling methods were generally developed merely for the in situ measurements. Nevertheless, the uncertainty of in situ measurements, such as measurement errors and spatial representativeness errors, was not dealt with. Consequently, the upscaling results inevitably suffer from errors, which will finally propagate into the pixel scale ground "truth." For the first time, this study presents an improved upscaling method with the consideration of the uncertainty of in situ measurements based on the error theory and measurement adjustment theory. The effectiveness of the corrected upscaling coefficients was evaluated by comparing the accuracy of the corrected upscaling results with those based on the upscaling coefficients without considering the uncertainty of in situ measurements. The results indicate that the accuracy of the upscaling results can be enhanced by 11.06% in the condition in which in situ measurements suffer from large uncertainty. However, if the uncertainty of in situ measurements is negligible, the corrected upscaling model is not necessary because it does not bring many benefits. Although the effectiveness of this method was only tested on a limited study area, it makes an important first step toward a higher precision pixel-scale ground "truth," especially when the uncertainty of in situ measurements is nonnegligible.