Post 2: Data Gathering

Goals and Objectives
The goal of this exercise was to learn how to download data from a variety of publicly accessible websites and manipulate the data into a form that was functional for our purposes. To do this, we needed to import the downloaded data into ArcGIS and join where appropriate. Finally, all data had to be compiled into a single geodatabase with the same projection.  The processed data will serve as the base data for our ongoing Trempealeau County frac sand project.

General Methods
Four different online sources were used to collect railroad, land cover, elevation, cropland, and soil data. These included the US National Atlas, USGS National Map Viewer, USDA Geospatial Data Gateway, and USDA NRSC Web Soil Survey (SSURGO) (Fig.1).

Figure 1. The data was downloaded from a variety of online sources.

To receive the data, various requests and form submissions were required at each site, which generally resulted in the download of a zip file.  The files had to be unzipped and desired files located.  This was not always straightforward. For example, the elevation data provided by the USGS National Map Viewer was delivered in multiple files due to the size of the data.  As we wanted a single elevation raster, we had to join the two DEMs together using the mosaic tool.  This step required we use the appropriate bit depth, so as not to lose any data in the process. Also, the SSURGO soil shapefile we wanted had to be imported into a feature class in our geodatabase. We then joined the soil information from the "component" table to the feature class based on a relationship class we created. Additionally, we joined drainage index and productivity index tables to the SSURGO data, using DI index as the symbology for the feature.

The data quality varied for each source and data set.  To ensure proper use of the data later in our project, data quality information was compiled from the metadata of each data set (Fig. 2)

Figure 2.  The data sets vary in quality, which will be important to be aware of in later aspects of the project.

Results
With all desired data collected, the final step was to project all the features in the same coordinate system. As our study focuses on Trempealeau County, I used "NAD 1983 UTM Zone 15N" as my projected coordinate system. To do this, I used the "project raster" tool for the land cover, elevation, and cropland features and the "project" tool for the railroad and soils data (Fig. 3). All the data sets appear to have been processed correctly.  They should work well as the base data for later project analysis.

Figure 3.  Layers are shown individually, as well as together (upper left).  

Sources
Concepts and Techniques in Geographic Information Systems
CP Lo, AKW Yeung - 2003 - Pearson Prentice Hall