Lab 3 - Determining the Quality of Road Networks

One way to measure the quality of a road network is to evaluate its overall completeness.  The idea behind this is that the more roads mapped within a given network, the greater the likelihood that the network has better coverage of a given area.  This was the focus of our lab this week.

Do note, however, that just because a network has more coverage does not necessarily make it more spatially accurate... those lines still need to be in the right place!  Our lab focused only on comparing the completeness of one road network against another for the same area - testing the spatial accuracy of a road network using points was covered last week (Lab 2).

Technical Notes

The first comparison metric is exactly what one might think: we totaled the collective line segments lengths per road network, and compared the results.  At first glance the TIGER Roads data is more complete than the Jackson Co. street centerlines data.

After determining these lengths we then needed to break down just how complete each road network was per grid cell.  We overlaid a grid (a series of square polygons) covering the whole of Jackson County, then split up the road network polylines by grid cell.  This was done using the Intersect (analysis) tool. 

Once the road segments were separated their respective lengths per grid cell were then updated using the Calculate Geometry tool.  The grid cell data was then joined to the road segments - this made it easier to obtain the overall road length totals per grid cell (per road network). 

The TIGER Roads were also shown to be more complete in terms of overall length per grid cell... but the Jackson County street centerline data is more complete in more grid cells than the TIGER Roads data.  The results are depicted in the map below.  A choropleth map using (Jenks) Natural Breaks was created, and the results are explained in terms of percentage variance for the Jackson County street centerline network from the TIGER roads data.




The final result, explained in terms of how it relates to the Jackson Co. street centerline data.