The methods described below and in the technical papers published by the University of Toronto's Office of Cartography26 have been peer-reviewed by academics in the fields of image processing, geographic information science, and urban geography.
Defining the built-up urban area boundary
The goal of the analysis was to accurately and conservatively identify the consolidated urban area in the region, as opposed to small, scattered urban features located far from large contiguous urban areas. Imagery captured by Landsat Thematic Mapper 5 (30-metre resolution) in summer 1990 was used. Due to cloud cover in the satellite imagery for north Simcoe County, no urban boundaries were created for Orillia, Midland, and Penetanguishene. (Given the small amount of growth in these municipalities during the study period, their omission had little effect on the intensification rate for Simcoe County.)
A classification was conducted in which each pixel in the satellite image is assigned to the class to which it most probably belongs: water, non-urban, or urban. After this initial classification, the data is refined to eliminate non-urban pixels completely surrounded by urban pixels, and vice versa. The result is a contiguous area representing the built-up area of a municipality.
Estimating intensification rates
Two census variables were employed in a three-step process to estimate 1991-2001 intensification rates for all upper- and lower-tier municipalities in the GGH.
First, all census dissemination areas (DAs) completely contained within or straddling the 1990 urban area boundary were selected. For these DAs, the census "period of construction" variable was used to sum all dwellings built between 1991 and 2001.
Second, the number of dwellings that fall outside the urban boundary was identified. This was done using census blocks, a very small geographic unit whose boundaries correspond to neighbourhood blocks, for which the 2001 census enumerated all dwellings. The number of dwelling units in census blocks of which more than 50% fell outside the 1990 urban area was subtracted from the DA sum in step one, yielding an estimate of the total number of dwellings located within the 1990 urban area built between 1991 and 2001.
Third, dividing the total number of dwellings located within the 1990 urban area and built between 1991 and 2001 by the total number of dwellings produced in the same decade yielded an average intensification rate for the period.
An additional analysis was performed to determine what proportion of intensification dwelling units are located near the 1990 urban area boundary. First, a near-edge area was defined as all land within a 500-metre distance of the 1990 urban area boundary and inside the boundary. Second, all DAs of which 90% or more was within the 500-metre buffer area were identified. Third, the census "period of construction" variable was summed for these DAs, yielding the number of dwellings built between 1991 and 2001 within 500 metres of the urban boundary.