Raster Points

Raster Points (i.e., Dissemination Area partitioning)

100m by 100m raster points were computed as follows:

  • determine the required latitude and longitude increments to move approximately 100m east-west and 100m north-south. In Saskatoon, the following values are very close:
      • Latitude increment: .00089893575680
      • Longitude increment: .00146049608306
  • compute 100m x 100m polygons inside a bounding box around Saskatoon, as shown in the following image. NOTE: Must work in lat/lng rather than UTM as the UTM coordinates DO NOT run perfectly east-west and north-south in Saskatoon. If the computations are done in UTM, the square raster point polygons appear slightly rotated as shown below.
  • Next, each computed raster polygon was compared to all June stop locations. Any raster polygon centroid farther than 1000m from the closest stop was discarded. This greatly reduces the number of raster polygons that must be considered in subsequent calculations (e.g., heatmaps, etc.)
100m_raster_ploygons.png

Above: 16,872 raw 100m x 100m raster polygons withing 1000m of a bus stop,

100m_raster_polygons_and_das.png

Above: Raster polygons for all DAs. Discarding raster polygons more than 1000m from a bus stop greatly reduces the number of raster points that must be considered in subsequent calculations

lat_lng_vs_utm_raster.png

Above: Left: Raster polygons computed using lat/lng coordinates. Right: Raster polygons computed using UTM coordinates.

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