Module 1.2: Data Quality Standards

In continuation of our module about Data Quality, this week we learned about how to determine the quality of road networks, determining postitional accuracy of two road networks by comparison and the methodology of procedures provided by the National Standard for Spatial Data Accuracy (NSSDA). We were given city data and street data shapefiles of Albuquerque, NM along with orthophotos to help us create reference points. From there we were able to create acccuracy statistics worksheets to create a formal accuracy statement per the NSSDA guidelines. Below is an image of my sampling locations.

Summary of steps: Once the reference points were created, I was able to calculate geometry in the attribute tables for city, streets and reference points to get the corresponding X and Y coordinates. From there I exported the data to Excel and created columns for error_x, error_y, error_xy_sqrd, error_xy, RMSE, Mean, Median, 95th Percentile, Minimum, Maximum, 68th Percentile,and 90th Percentile. The NSSDA statistic is determined by multiplying the RMSE (root mean square root) to a 95% confidence level. 1.7308 for horizontal accuracy and 1.9600 for vertical accuracy. For this project horizontal accuracy was being determined. The following statement is the accuracy statement once I multiplied my street RMSE by 1.7308 and my city RMSE by 1.7308.

Street Map Data: Tested __141.6709___ feet horizontal accuracy at 95% confidence level.

City Data: Tested __17.9350___ feet horizontal accuracy at 95% confidence level.