M1.3: Assessment

 For this lab assignment, we were to complete an accuracy assessment of the road network data from two different sources for Jackson County, Oregon to determine their completeness. My methods to complete this task were as follows:

1.    I started by using the “Pairwise Intersect” tool for each of the road shapefiles to isolate each of the road segments within the grids

2.    Within the attribute table of the two new shapefiles the previous step created, I added a new field and used the “Calculate Geometry” tool to get the length of each road segment in kilometers.

3.    I then used the “Summary Statistics” tool for each shapefile to combine the lengths of each road segment based on their grid code.

4.    I used the “Join Field” tool to join the two resulting measurement fields to the grid attribute table to compare them.

5.    I created a new field in the grid attribute table called “comparison” and calculated the field using the following code: ["ST More" if !SUM_ST_Len! > !SUM_TIGER_! else ("TIGER More" if !SUM_TIGER_! > !SUM_ST_Len! else "Equal")]. 

6.    Then I used the "Summary Statistics” tool to determine how many grid polygons had more complete TIGER roads versus the Street_Centerlines.

7.    I added another field to the grid attribute table for which I calculated the percent difference between the two sets of road lengths for each gridcode.

8.    Finally, I changed the symbology to graduated colors to reflect the differing completeness of the road data for each grid polygon.



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