Determining Appropriate Neighborhood Window for Neighborhood Analysis

The increasing use of gridded data in earth sciences or in hydrological estimations demands the application of mathematical approaches, especially geo-statistical ones, in obtaining accurate data. Since gridded data are generally generated from the interpolation of point data and/or processed satellite images, the use of neighborhood analysis is unavoidable in attaining more accuracy. On the other hand, in any neighborhood analysis, one is to be mindful of the selection and/or introduction of appropriate neighborhood window in terms of shape and dimension. As square or circular shapes (default shape) are usually used for neighborhood windows, an attempt has been made in the present study to address the acceptance condition of the default shape and to determine an appropriate window shape. To do so, use of image of surface semi-variogram (extracted from a geo-statistical approach) was proposed. The proposed approach was validated by determining the area of the plains in the Roodzard basin of Khozestan in Iran and extracting the channel network of Walnut Gulch Experimental Watershed (WGEW) in the State of Arizona in the United States. The findings of the study showed that the adoption of an elliptical shape for neighborhood window in extracting the Roodzard basin landform layer, led to 28 percent (93 Km2) change in the plain area extent in comparison to a square-shaped window, which will surely affect the scopes of terrain management of the basin. They also indicated that the use of a neighborhood window in WGEW led to 96 percent correspondence of the existing channel network with the extracted channel network in comparison to a circular (or circle-shaped) window.