Road Completeness

 This week, I completed an accuracy assessment of two road networks based on their relative completeness using 1km x1km grid for comparison.  The goal of this assessment was to determine which road network is more complete.  TIGER Roads or Street Centerlines, and to determine which locations are similarly accurate and which locations are more accurate with either of the two networks.  The method ology I used to achieve this is outlined below.

I first used the “Clip” tool to remove portions of each road network that were outside of the supplied grid network.  Once the roads outside of the grid area were clipped, I used the “Summarize Within” tool to calculate the lengths of the road system inside each grid polygon.  I specified the output in kilometers so as to eliminate the need to do a separate calculation to convert the results from feet.

Once I had the total feet for each grid and road dataset, I used the “Table to Excel” tool to export this information to Microsoft Excel and calculate the necessary statistics in order to produce the table and maps below.  Once the statistics were calculated, I used the “Excel to Table” tool to import the final Excel table back into ArcGIS.  Once in ArcGIS, I used the “Join Field” tool join the Percent Difference field I created in Excel to the Grid layer.  I then used this field and the Grid layer to generate the map.

As evidenced by the map, the completeness of the road network is within +/- 5%, but there are areas that diverge a lot based on the accuracy of each network as it relates to specific grids.  

TIGER_Roads total length in kilometers: 11,382.7

Street Centerlines total length in kilometers: 10,873.3

The TIGER Roads network is more complete based on this analysis.

Total Grid Cells	297
Cells Where Street_Centerlines is more complete than TIGER_Roads	134
Cells Where TIGER_Roads is more complete than Street_Centerlines	162