Simulating Locational Error in Field-Based Measurements of Reflectance

Measurement error may be a large component of the total variation encountered in environmental variables. Therefore, for environmental analyses measurement error in sample data should be acknowledged and quantified. Further, it is important to understand how the variogram is affected by different kinds of measurement error. In this paper, a survey of field-based reflectance was undertaken in such a way as to allow the estimation of both the sample variogram γ z (h) and the component of the variogram due to measurement error γ e (h). The underlying variogram γ u (h) of true values u(x) was represented with a simple function. Then sequential Gaussian simulation was undertaken to introduce, via a locational error (δy), a measurement error e s (x) into the underlying true values u s (x) to give a set of ‘observed’ values z s (x). The results demonstrated the effects of locational error on the sample variogram γ zs (h), and in particular a negative cross-correlation between the underlying values and measurement error that results from a locational error. In addition, it is shown that the component of the sample variogram of reflectance due to measurement error γ e (h) could not be explained solely by a locational error δy.