Special Topics Week 3: Assessment of Data Quality

Continuing with our exploration of data quality, this lab focused on different methods of assessing the relative completeness of two different road networks for Jackson County, Oregon: a street centerline network, and the TIGER 2000 network. We followed a similar methodology to Haklay (2010). The first metric was comparing the total length of the roads in each network. Next, we divided the roads into segments for each 5 km x 5 km grid cell in order to assess which network had the greater length in each cell.

My process involved projecting the TIGER network into the same spatial reference system as the Street Centerlines network, clipping both networks to the extent of the grid, and taking the intersection of each network with the grid in order to segment lines based on the grid cells. I then used Summary Statistics to calculate the sum of the road lengths for each grid cell, and Join Field to add these sums to my Grid table for each grid cell. I added a field to my Grid table and used Calculate Field with a code block that evaluated each cell as 1, 2, or 0 based on which network was longer.

I found that the TIGER network was longer in 162 cells, and the Street Centerlines network was longer in 134 cells. There was one cell for which both lengths were calculated as 0, although both networks had roads in it.

The third method of evaluating completeness used a percentage that represented the difference between the Centerlines and TIGER lengths divided by the Centerlines length. These percentages are displayed on the map below, in which the pink cells are ones in which TIGER is more complete, and blue cells are ones in which Centerlines is more complete. Based on all three methods of evaluating completeness, it is clear that the TIGER 2000 network is more complete than the Street Centerlines network for Jackson County.


References:
Haklay, M. 2010. How good is volunteered geographical information? A comparative study of OpenStreetMap and Ordnance Survey datasets. Environment and planning B: Planning & Design, 37(4), 682-703.

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