GIS 5935 Special topics Module 3

 

Module 1.3 

Jackson County Oregon Road data Quality

In this module we compared the quality of road data from two different sources in Jackson County Oregon. 

For the most part the module was very straight forward but it did require me to pull out some older knowledge of GIS tools in order to work through it. 

    Briefly describing my analysis steps I’ll start with the reprojection of the Tiger_Roads layer to the Street_Centers layer. For this step I used the reproject tool and then removed the old featureclass from the contents pane.

The next step required me to clip the road lines that extended beyond the grids. In order to accomplish this I used the dissolve tool to dissolve all of the grids into one polygon using the ID field.

I then ran the intersect tool for both road network layers against the new dissolved grid layer. This removed all and any road segments that extended past the boundary of all the grids. This process created two new road network feature layers that I named %name%_intersected. After this, the dissolved grid was not needed to I turned it off in the contents pane but didn’t remove it.

I then used the summarize tool on each of the road layers to get a total length of all polylines in each table. This created two new tables with one line in the attribute table with the total line length.

Calculating the total length of the road segments required me to determine which measurement type the road networks so I went to the properties of each layer and learned that the measurements were in US Feet. I needed to convert this to Kilometers so I added a new field to each road attribute table and then performed a field calculate for the new empty field. In the field calculate tool I chose the field I was importing into the calculated field and then multiplied the value by 0.0003048.
This is the conversion need to get from US ft measurement to Kilometers.

So the script for the calculate field tool looked something like “shape_length*0.0003048

I completed this process for both streets_intersected layers to get the value in Kilometers for each.

I then moved the percentage difference per grid field into the grid layer so that I could create a choropleth map for my final layout. 

I added two smaller inset maps to help the reader understand where on the planet this study area is in. 

The map has legend, scale bar, north arrow and source credits to complete the map elements.