preparation of the topographic factor (ls) map in rusle model is a very tedious step because of the complicated effects of topography on soil loss. the objective of this study was to determine the suitable cell size of digital elevation model (dem) for computing ls factor by the method of moore and wilson (1992) in a 5326 ha area, northwest of tehran province. towards this end, cell sizes of 30...

The paper reviews both the influencing factors and calculation strategies of sample size determination for survey research. It indicate the factors that affect the sample size determination procedure and explains how. It also provides calculation methods (including formulas) that can be applied directly and easily to estimate the sample size needed in most popular situations.