1. A method of loading three-dimensional (3-D) image data in a navigation system, comprising: determining whether a vehicle enters an intersection while traveling; selecting a mask array based on a travel path of the vehicle; selecting an object to be displayed at the intersection and selecting a level-of-detail array of the object depending on a distance between the vehicle and the object; and overlapping the level-of-detail array of the object with the mask array and displaying the object depending on the level of detail of the object obtained from the overlapped arrays.