GIS5935 - Lab 2 - Determining Quality of Road Networks

Our task this week was to evaluate the quality of two different road networks for Albuquerque, New Mexico.  The first step was to create "New Network Datasets" for each of the provided street shapefiles.  This generated "junction" point shapefiles for each street network.  

Next, using examples of good intersections I identified twenty "test" points using the ABQ junctions.  The overall criteria was to be:

1. a "good" intersection 

2. Meet the sampling rules (min of 20% in each quadrant and > 10% of diameter apart)

3. Matching locations in both street datasets

I used the draw tool to "eyeball" the quadrants and diameter of the "study area" so my test points would meet the 2nd criteria.

I used the ortho images provided to create a new "reference" shapefile and digitized reference points using the twenty test locations from the ABQ junction dataset.

In order to compare each street dataset with my reference set I added a short integer field to all three shapefiles (reference, ABQ_Streets, StreetMapsUSA).  It took a long time to edit the attribute table of each shapefile.  

Using the AddXY Coordinates tool, under Data Management Tools > Features, I was able to quickly add the X and Y coordinate values for each point in the three shapefiles.

I used the table to Excel tool to convert the attribute tables of my three shapefiles to Excel.  I combined all the Excel worksheets into one workbook and used the provided NSSDA spreadsheet to calculate the necessary values.  The following results were reported.

StreetMapUSA Road Network

Horizontal Positional Accuracy           Tested 367.260 feet horizontal accuracy at 95% confidence level

ABQ_Streets Road Network

Horizontal Positional Accuracy           Tested 18.810 feet horizontal accuracy at 95% confidence level

This was a very time consuming lab assignment for me but I realized the importance of data quality.

Twenty Reference/Test Points Used to Determine Horizontal Accuracy of Two Different Road Networks