Module 3 - Assessment

    This week, in the third Special Topics in Geographic Science lab, was about assessment with concerns to data quality. 

    In this lab, we did an assessment on road lengths in Jackson county Oregon. This was done in order to give us more experience with assessing the accuracy with concerns to road length data. As you will see in the the map below we had taken the full lengths of our road files, Tiger and Centerlines in order to preform a percent difference evaluation between them. With the full lengths between the two road lengths being Tiger Roads with 11,382.7 kilometer and Street Centerlines with 10,805.8 kilometers. 

    As for how we got the map, we did some analysis. So, to start I used the clip tool to obtain both road lengths contained within the provided grid. This trimmed out any toads that had left the grid so all the data could remain within the grid. Next, since my data for the road lengths was already in kilometers to begin with earlier in the lab, I then used the summarize within tool. This tool summarized all the road lengths within each grid section, and this was done for both files separately. Lastly, both files were joined using the spatial join feature so the calculations of percent difference could be input into a new field and used for the map.

    As for the results, the negative percent difference in the calculations and the map show that there are areas where tiger has more length than centerlines. The opposite direction with positive values show that centerlines has more length than tiger. With the middle values around the -5 and 5 percent range showing minimal difference.

    Overall, this was another great lab in providing more experience and technique into using ArcGIS as well analysis of data. 



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