GIS I - Lab 2: Downloading GIS Data

The image on the left shows the total population as population density per county with a darkening color ramp to illustrate higher values. The image on the right shows the number of 20-24 year olds per county described by percentage of total population.

Goal

Background: The goal of this assignment was to create a map based on data downloaded from the United States Census Bureau.

Purpose: The purpose of this assignment was to gain a better understanding of how to acquire data from various sources and use it for the creation of maps.

Methods

Step One: In order to collect the data needed to construct the maps, the United States Census Bureau website was used to initially acquire the data. Using the website, the data was found by narrowing down certain parameters. For this exercise, the "Basic Count/Estimate" for population was selected, followed by Wisconsin Counties, followed by the "Total Population". This data was downloaded as a zip file and the was unzipped to the lab folder. Two comma-separated values (CSV) files were  located in this file. One of these folders contained metadata concerning the data in the other CSV file. The other file contained all of the data, laid out in a table format. Both of these files were opened using Microsoft Excel and converted to an Excel Workbook by saving them as such. This allows the user to use the data in programs such as those in ArcGIS. 

Step Two: After converting the CSV files to Excel files, they were able to be utilized in ArcMap. First however, shapefiles were downloaded through the Census website. They were downloaded as a zip file like the CSV files, unzipped, and the shapefile was extracted and placed into ArcCatalog. From ArcCatalog the saved Excel files are able to be copied and placed into the ArcMap file with the newly downloaded shapefile. From here, a table join is conducted in order to link the Geo_ID field from the shapefile with the Geo#ID field from the Excel data. This can happen because the two attribute tables share this field, the field type, and the character with (the necessary requirements for a table join). 

Step Three: Now that a table join has been carried out, the ability to map population data is available. In ArcMap, the shapefile feature class is right-clicked, Properties is selected, Symbology is selected, and the Graduated Color option is used to distinguish between different classes of population. The data was classified into seven classifications based on natural breaks in the data collection, known as "Jenks" classification. Following this, the proper pieces were added to make the map understandable and useable by others. This included a North Arrow, Legend, Scale, Title, Author, and Source.

Step Four: The same work flow was carried out again for another set of data. The data was gathered from the Census Bureau, this time using the Age Group and Sex: 2010 dataset. It was downloaded as a zip file and extracted, added to a new layer within the same ArcMap file as the first, joined by the Geo_ID field and was then able to be manipulated. In order to properly show this data through map visualization the data needed to be normalized. The data for Age Group 20-24, Both Sexes, was normalized with total population to properly display the actual percent. The map was assigned a graduated color scheme and proper map items as described before.

Results
This exercise was able to show that there are many different places to find data that can be used for maps. It showed how to convert tables and implement them for use in ArcMap.  It also taught how to join tables for use in mapping. Finally, it familiarized me with the Census Bureau website, which is key to utilizing and analyzing demographic data for different purposes.

Sources:
Zach Hilgendorf
United States Census Bureau