First,the marketer needs to define the extent of the market area.A concept used in the retail industry is that of the critical trading radius was initially conceived as a system of conceived as a system of concentric circles of mileage, with the facility location as the center and 5-,7-,and 10-mile(8-,11-,and 16 kilometer) radii as milestones. because of the variance in traffic congestion and in some cases the absence of a direct route,the concept has been redefined as a series of radii based on customer traveling time to the sport facility rather than straight mileage