GIS4930 Lab 2: Data Quality Standards

This was a fun lab. In it, we started with a two line shapefiles of Santa Fe, NM streets, and a large set of ortho imagery, which we had to add to the map.

We then selected 20 roadway intersections on the map, with over 20% per quadrant and meeting other NSSDA standards for sampling (i.e. over 10% of the radius distant from each other). From there, we created point data for the both roadway sets, then found the "correct" point as a reference by looking directly at the ortho images. We then assigned XY values to each point, then used a positional accuracy worksheet from the National Standard for Spatial Data Accuracy to calculate the difference in X and Y values, their squares, the sum of their squares, and finally the sum, average, Root Mean Square Error and the NSSDA accuracy statistic.

If you're in this program and are searching out blogs to find examples for this lesson, here are two helpful hints:

1: Your initial orthos will be missing a lot. It's not documented anywhere, but there's a subfolder in the data you extract called "missing orthos".

2: the instructions will tell you to export the attribute tables as DBF files. I found it to be a lot easier to use the Table to Excel tool.