The lab this week compared the percent difference between road two center line datasets in Jackson County, Oregon. One dataset originating from Jackson County GIS and the second the US Census TIGER/Line Shapefile for the same area. First all the supplied feature classes where imported into a file geodatabase and transformed to the Oregon State Plane, projection coordinate system (PCS). Other feature provide were a 5 km by 5 km grid and the Jackson County boundary.
For each of the road center line features the following actions where performed:
- Using the intersection tool to "clip" each road center line feature to a grid cell.
- Added a GRID_ID field
- Spatially join the grid to the road center line (intersect) and used the filed calculator to populate the GRID_ID field
- Use the Dissolve too to aggregate the road center line in each grid by the GRID_CODE, effectively creating a single line feature per grid cell
- Update the LENGTH field for in the dissolved feature to have the total kilometers of of road center line.
Once the total kilometers of road center line is added to the dissolved center line features:
- Added three fields, JacksonLenght, TigerLength, & Difference
- Join the two dissolved feature using the GRID_ID & GRIDCODE attributes
- Use the field calculator to populate the field length and difference fields
The outcome of this process is to establish a metric for completeness for the road center line in each grid using the TIGER/Line Shapefile feature as the control. The outcome is shown in following map and table.
Description |
Count |
Area (km2) |
% of Total |
TIGER more complete |
126 |
3,150 |
42.42 |
No. Grid Jackson County more complete |
170 |
4,250 |
57.24 |
Empty |
1 |
25 |
0.34 |
Total |
297 |
7,425 |
100 |
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