Figure 3From: Measuring geographic access to health care: raster and network-based methodsConversion of vector road data to raster cells. The original roads (black lines on left) are converted to a cell-based representation with large cell sizes (middle), resulting in an overconnected travel grid. Smaller cells (right) improve the topological structure of the travel grid. However, the two roads are still erroneously connected in this scenario.Back to article page