Abstract
The shade caused by forests is estimated by creating a GIS drawing of the average distribution of forests using numerical cadastre data and adding the postulated or measured tree height to the mesh altitude for that forest. We tested the precision of this method on a flower farm located in a hilled rural area of Kochi Prefecture. We estimated the area of shade based on the measured tree heights of a nearby forest that shields the farmland, and compared it with the area obtained from photographs that have varying sun elevations. Based on these results, we clarified the reason of error occurrence. Following analysis of precision for this method, it became clear that most of the farm was shaded only by nearby forests when sun elevation reaches a maximum in autumn and winter. The effects of partial forest cutting on changes in the shaded area can be simulated by this method using the assumption that tree height in any cut area is zero meters.
