As the construction material of the building is different hence building detection is critical task from the HRI. The image qualities, resolution, weather type of image sensor are important factors to produce accuracy. Building detection in dense urban areas having problems due to factors like shape, size, color and texture, and image sensor. For the find, the building has to consider the characters of the building like contrast, shape, and the building allocation in high, low, and medium density. In the present study, the mathematical morphological operation is used for the separation of the building. The building is indicated with a boundary.