Anyone who has used the GPS mapping application on their phone or computer is familiar with Geographic Information Systems (GIS), even if they don’t know it by that name. GIS combines geographical elements (places, roads, buildings, etc.) with various information (population, speed limit, date of construction, traffic etc.), which are utilized to solve real problems (such as finding the fastest route to your destination). Civil engineers use online GIS sites or Google Earth to gather basic preliminary information on a project site such as aerial images, property boundaries, flood plains, etc. It’s particularly useful when we don’t yet have a survey. GIS software can also be used to create attractive map documents for presentations. However, simply viewing GIS data or creating a map leaves out a very key letter in the GIS acronym: “I” for information. The real power of GIS lies in combining the geographic elements with related information to produce data-supported solutions.
For civil engineers, the quality of a city or county’s online GIS mapping website greatly affects the amount of time it takes to gather info on zoning and other jurisdictional requirements. But GIS can be much more powerful than just viewing data interactively online. Some cities have basic data available for download from their website for free. Other cities will send you data, such as parcels, roads, utilities, and contours, at your request. This data can be especially useful in the early stages of design for a new site, when a full survey has not yet been completed and you want to ensure the proposed layout will work. Most often, we import GIS files into CAD software for preliminary design, but CAD doesn’t have the “I” information component of GIS, so all it can do with the files is show them as lines. If you bring these files into a GIS software, such as ESRI’s ArcMap, you will notice that they have data associated with them. For example, parcel GIS data files typically will have the owner, address, parcel ID, and the parcel size. GIS data such as this can be leveraged in various ways using the many tools provided with GIS software.
A few ways GIS can be used to solve problems:
- Find the drainage basin draining to a particular point. This analysis requires a Digital Elevation Model (DEM), which is a type of raster containing cells with elevation data. Using the spatial analyst extension in ArcMap, a watershed can be produced that will outline the total area draining to a specified point.
- Selection of a site based on various constraints. In the planning stages of a project, GIS software can be utilized to aid in selecting a site for a new development. For example, a client wants to find a new site for their restaurant with the following stipulations: it must be within 0.25 miles of an interstate exit, can’t be in a floodplain, must be currently vacant and flat, and won’t require rezoning. You could use the city’s online GIS map to manually search through all existing sites, selecting the ones that meet these criteria. Or, assuming the data was available, you could utilize your GIS software to “weed” out sites and areas that did not meet the criteria, essentially letting the software analyze the data for you.
- Transportation network analysis. Using the network analyst extension and various tools, you could use GIS software to find the shortest route between points and perform other transportation related analyses. You can assign your own parameters and constraints, such as number of lanes, speed limit, and width, so that the shortest path isn’t just based on distance. This sort of analysis could greatly aid traffic engineers and transportation planners.
So, when you hear the term “GIS,” it’s important to note if it’s in reference to existing GIS output such as maps, etc., or if it’s in reference to a GIS software program. While it’s most common to simply view GIS data on municipal sites, it’s helpful to recognize the value of the deeper, more analytic tools offered by GIS software. Utilizing GIS software for analysis like those in the examples mentioned above could produce faster, more accurate work – always a great goal to have.
About Nathan Spence
Nathan Spence, EI, is a Project Analyst for Foresite Group's Land Development – East Division in Auburn, Alabama. Nathan graduated from Auburn University with a Bachelor’s Degree in Civil Engineering. He has a background in GIS, transportation, and commercial land development. In his spare time, he enjoys racing bicycles across the southeast.