Abstract
This study tries to measure accessibility at building scale on GIS as the shortest road distance to convenience stores from all buildings (25, 359) in the northeast area of Adachi ward, Tokyo. As the result of examining the detail distribution of accessibility, it becomes clear that the distribution is determined by various factors such as road network pattern, positional relationship between facilities and road network, positional relationship between buildings and road network, and positional relationship among facilities.
Next, the accessibility at neighbourhood scale is measured at the centre of neighbourhood. In comparison with the accessibility at building scale, the worst level of accessibility disappears due to the smoothing effect of aggregation in the measurement at neighbourhood scale, but the average level of accessibility in the study area was slightly worse. As 80% of the convenience stores are located along main streets constructing the boundaries of neighbourhoods or outside them, average distance becomes longer because the centre of the neighbourhood is distant place to convenience stores in comparison with the buildings located along main streets. Therefore it is revealed that the positional difference between the buildings and the centres of neighbourhoods causes an ecological fallacy between building and neighbourhood scales.
Finally, the inner variation of accessibility within neighbourhoods is analyzed. While the neighbourhoods with good accessibility have small inner variation, those with normal accessibility have large inner variation. It is pointed out that there is a limitation to measurement at neighbourhood scale, because the centres of neighbourhoods are not representative when their inner variations are large.
