Primarily there are two aspects : 1 ) the calculation model of the value of land classifying units - - model of time distance attenuation . in the calculation model of the value of land classifying units , author brings forward the model of time distance attenuation . in this model adopting the network analysis , and by establishing the road network , and proceeding path analysis , computing the time distance , then proceed the exponential attenuation or straight line attenuation on time distance , get the value of influence factor of the land classification unit 主要有兩個方面: 1 、定級單元分值計算模型? ?時間距離衰減模型在定級單元分值的求取模塊中,提出了時間距離衰減模型,模型中采用網絡分析的方法,通過建立道路網絡,進行路徑分析,求取時間距離,進而按時間距離進行指數衰減或直線衰減,得到定級單元因素因子影響分值。