Investigating the sphere of influence of the city of Hamedan based on the theory of separationtheory and mutual impact

Sphere of influence has a huge impact as the determinant of the role of the city. The extent of urban sphere of influence is also related to the number and range of its roles. It means that the sphere of influence gets wider ,as the city's roles increase. The present study is an applied-purpose objective and in terms of the method, it is descriptive-analytic. The information collection methods included the library method of research and field observation. In this study, the separation point theory and cross point theory have been used to investigate the sphere of influence of Hamedan. In order to identify the domains of urban spheres of influence and to determine the domain of Hamedan, in this model we use the visual method to confirm or disapprove this domain. For this purpose, 27 cities of Hamadan are considered and the required information is obtained through the periodic censuses. The results show that in the years 35 and 45 Nahavand ,Malayer and Touyserkan had quite a large sphere of influence and in year 55 Nahavand and Malayer had the equal sphere of influence and in year 65-95 Malayer , Nahavnd and Touyserkan had quite a large sphere of influence among other cities of Hamadan .also ,according to studies , it is clear that as the population and distance increase , the sphere of influence rate increase .