Module 1.2: Data Quality - Standards

 

Figure 1: Overall Data Points

To complete the NSSDA accuracy assessment, I started by preparing three point layers: the ABQ city test points, the StreetMapUSA test points, and a set of reference points digitized directly from the orthophotos. I made sure all three point layers were in the same projected coordinate system and verified that each set of points aligned correctly on the map. 

After digitizing the reference intersections, I added XY coordinates to all three layers and exported the attribute tables into Excel. In Excel, I calculated the change in X and Y coordinates for each intersection, squared those values, and computed Error², the average Error², RMSEr, and finally the NSSDA 95% accuracy value for both datasets. 

I initially ran into issues with a few mismatched rows, but once corrected, the results stabilized and produced realistic accuracy values. Based on the final calculations, the ABQ city streets tested at 20.31 feet horizontal accuracy, and StreetMapUSA tested at 154.38 feet horizontal accuracy, both at the 95% confidence level according to NSSDA standards. Thus, the ABQ city map was much more accurate than StreetMapUSA.