Automatic measurement of building setbacks and streetscape widths and their spatial variability along streets and in plots: integration of streetscape skeletons and plot geometry

Abstract Measuring building setbacks and heights along streets is important for evaluating the variability of streetscape skeletons, the 3D spaces of streets defined by the arrangement of surrounding buildings. Its evaluation requires computing the streetscape width, defined as the front road width of a building plus the setbacks of both sides of the front roads, the building heights and the ratio of the streetscape width to the building height, known as the streetscape width-to-height ratio. However, measuring building setbacks and streetscape widths with geographical information systems (GIS) workstations remains theoretically and technically challenging because conventional methods fail to define the ambiguous boundaries of streetscape skeletons. To address this issue, we developed a new method for defining and measuring building setbacks and streetscape widths automatically and in a consistent way. A new basic spatial unit was also developed for evaluating the variability in building setbacks, heights, streetscape widths and streetscape width-to-height ratios not only in plots focusing on classical urban morphologies but also along streets focusing on a pedestrian perspective. The method contributes practically to the measurement and evaluation of streetscape skeletons in a bottom-up way at fine intervals without the need for setting predetermined spatial units. KEY POLICY HIGHLIGHTS Measuring building setbacks and heights along roads is important for evaluating the variability of streetscape skeletons. However, measuring these in an actual complex urban space without vagueness on a GIS workstation is difficult. We have developed a new method for defining and measuring building setbacks and streetscape widths automatically. A new basic spatial unit for evaluating streetscape skeletons is proposed focusing on the plot geometry and a pedestrian perspective. The method contributes to the evaluation of streetscapes in a bottom-up way at fine intervals without setting predetermined spatial units.