REMOTE SENSING OF ENVIRONMENT 25:323-348 (1988) The Use of Variograms in Remote Sensing: L Scene Models and Simulated Images

Extraction of information from remotely sensed images would greatly benefit from increased use of spatial data. However, the utility of spatial data has been undermined by a lack of understanding of the nature and causes oI observed spatial variation in images. One approach to this problem is to model the spatial vaiiation in images as a function of ground scene and sensor parameters. Variograms are the tool used to link models of ground scenes to spatial variation in images. Explicit vaxiograms are calculated for simple models oI ground scenes consisting of randomly located discs on a continuous background. By incorporating the effect oI the IFOV of the sensor through a process called regulaxization, explicit variograms for images of these scene models are derived. Verification of the explicit variograms i accomplished by simulating images that match the assumed scene model and sensor parameters and calculating empirical vaxiograms |or these images. For a simple scene model oI randomly located discs on a continuous background, explicit and empirical variograms match, verifying the convergence of these two dissimilar approaches. The sensitivity o [ vaxiograms i studied through varying parameters of scene models both in calculating explicit variograms and in simulating images. Results indicate direct ties between several scene parameters and the behavior of vaxiograms. The height o | the sill of the variogram is related to the density o | objects. The range of influence is related to the size oI objects. Increased variance in the size distribution oI objects results in a more rounded shape in the variogram near the sill. Primary effects oI increasing the units oI regularization, or larger pixel size, axe a decrease in the height o the sill and an increase in the range of influence. 1