An Introduction to GIS and its Applications
Avid hikers likely find themselves reviewing trail and topographic maps, city residents probably check bus routes often, and anyone who has kept up with an election has certainly viewed county, state, and national maps to track votes. These maps are generated through an intricate system called a geographic information system, or a GIS.
Geographic information systems
A GIS is a computer system that stores, analyzes, and displays geographically referenced data and information and connects that data to a map (USGS, National Geographic, ESRI). The system allows individuals to better visualize trends and patterns in spatial data and see relationships before jumping into statistical analysis. In short, GIS is used to answer the question, āwhere?ā. āWhere are bike racks located?ā and ā Where are the buildings on the school campus?ā are just two of the endless āwhereā questions that can be asked of a GIS. More sophisticated questions that require analysis can also be answered in a GIS: What are the cities that are most at risk of flooding? What is the most suitable location for a solar farm? These questions require geostatistical analysis - the prediction of values associated with spatial data (ESRI).Ā
Geospatial data
GIS data, often referred to as GIS layers, must be brought into a GIS software and displayed using georeferenced information. GIS layers come in two forms: vector data and raster data. Vector dataĀ is data that is stored as a point, line, or polygon while raster dataĀ is continuous data that divides the representation of the world into cells that have their own value. Generally, raster data is used as the backdrop to display vector data. Examples of vector data include:Ā
Points: single trees, survey plots, and schools
Lines: rivers, roads, and electrical lines
Polygons: buildings, lakes, and forest, state, or zip code boundaries
Raster data can be thought of as a photograph where each pixel is the cell and each pixelās color is the value. In the context of GIS, the cell values often represent temperature, rainfall, or elevation (Spatial Vision).Ā
Data is usually layered on top of each other in a GIS to create context. For example, take the image below which shows a single layer of point vector data. What do the points represent? How far away are the points from each other? What neighborhood, city, or state are the points collected in? Without context, it is impossible to accurately answer these questions.
Letās add a layer. The new layer is some type of boundary and only adds a small amount of context to the first point vector layer as it does not immediately help answer those pending questions above. Weāll add one final layer to this map
Now, if we are familiar with the San Francisco area, we can see that this map - though still quite a lacking map - displays point vector data across a polygon vector layer that is overlapping raster data in the form of satellite imagery. Without a legend, it is impossible to know what the points and polygons represent, but the overall takeaway is that layers provide context and help show spatial patterns (hint: the points represent significant historic sites and the polygon is the park boundary of Golden Gate National Recreation Area!).
Applications of GIS
Applications of GIS intersect hundreds of different fields including landscape architecture, engineering, public health, and even history. The development of the software has allowed researchers to leverage geostatistics to create visualizations for hundreds of topics. Specifically, GIS has allowed the environmental field to flourish through geostatistical applications and visualizations.
Natural resource management: research geographers and foresters use GIS to track landscape-scale changes from development, deforestation, and impacts of urban heat islands.Ā Ā
Hydrology: hydrologists can determine areas at risk of various scenarios of sea level rise and flooding events.
Wildlife biology: wildlife biologists and conservation technicians utilize GIS to understand wolf pack populations, bird migration patterns, and animal movement trends.
Soil science: agrologists, pedologists, and farmers can ascertain soil health and site suitability for crops based on soil moisture, nutrient availability, and organic matter content.Ā
Environmental justice: racial inequalities relating to access to green space, gentrification, and redlining policies are visualized in a GIS.
Transportation: hiking trails, bus lines, and walking paths are mapped to give users the knowledge of sustainable transportation options.
GIS is a fantastic tool to observe large-scale areas that are not feasible to monitor by taking in-situ (in place) measurements. This software allows researchers and stakeholders to gather data on an area and allocate funds based on the needs of the space. If you would like to learn more about GIS and its applications, I recommend starting with ESRIās Modern GIS: Introduction to GISĀ webpage.
About the Author
Claire is serving her second AmeriCorps term, but first VISTA term, with Truckee Meadows Parks Foundation. Claire grew up in Seattle, Washington but has since moved around the United States. She received her bachelor's in Geology with GIS and statistics minors from Macalester College in St. Paul, Minnesota. After school, Claire moved to Louisiana to do statistical machine learning and GIS analysis for the U.S. Geological Survey. Following this position, she found her way back to the west and settled in Incline Village, Nevada where she currently lives. In her free time, she can be found climbing peaks throughout the Sierra Nevada and making art.Ā
Thanks for the breakdown!
Very interesting article. Thanks!
That's really cool. I learned so much from reading this!