Analyzing completeness

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In my special topics course, we have been learning about accuracy assessment. This week we focused on completeness and learned how to analyze completeness. The goal of analyzing completeness is to understand how much data is missing. Haklay (2010) argued that accessing completeness helps us understand how useful the data is. 

We were given two road networks of Jackson County, OR, and a grid polygon to carry out the analysis. The networks were from TIGER 2000 and a local street centerline network. I began my analysis by using the batch clip tool to remove any parts of the road networks that were past the boundaries of the grid polygon. Next, I used the intersect tool to intersect each network with the grid layer. I used this tool because it created a new layer with the two layers joined together. I recalculated the sum of the networks’ lengths in kilometers. Then, I used the summarize within tool on both networks. I used this tool because I was able to choose which attributes I wanted to focus on and it was easy to use. 

Now I needed to begin my analysis. To begin this, I used the table to excel tool to convert the attribute table to an excel document. I made a new excel document that contained the grid codes and the TIGER and street centerlines sum lengths for each grid. I manually counted the completeness of each grid because I found this to be the easiest and quickest way to tally the completeness. Next, I used this excel document to calculate the percent change with the formula given in the lab instructions. I created another excel spreadsheet to which I added the grid codes and the percent change values. 

Next, I needed to add these values to the project to complete my map layout. I used the excel to table tool because that is the best way to move the data into an attribute table. Once I converted it into an attribute table, I used the join tool to join this table with the grid layer. From here I was able to symbolize the grid layer with the percent change values. I had to symbolize with the custom field option. I then created my map layout, which is included below.




References:

Haklay, Mordechai. (2010). How good is volunteered geographical information? A comparative study of OpenStreetMap and Ordnance Survey datasets. Environment and Planning B: Planning and Design, 37, 682-703.  

 

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