A viewshed approach on identifying the street spatial outline

The street space plays an important role in urban fabric studies. However, it´s difficult to draw continues contour line of the street space because of the gaps between the dispersed buildings, especially in China cities. The paper developed a new method to extract the street spatial outline and indentify the perceptible street space with the cumulative viewshed analysis in GIS. Through the cases study of the sample streets of seven typical cities chosen from US, Europe and China, the visibility of every pixel of the sample streets was calculated with cumulative viewshed analysis. With the threshold which was set based on the statistics analysis, the street spatial outline was extracted and the street space was identified. The results show the new method for identifying the street space is effective. The extracted street space reflected the characteristics of spatial form and presented a new concept to study urban fabric.