Advanced 3D Mapping Helps EPA Make Critical Decisions

Across the United States, communities of all sizes are facing the need for increased, sustainable access to freshwater resources as demand rises. Due to increasing challenges and changes in climate, a 2013 survey conducted by the Government Accountability Office found that water managers in 40 states expected freshwater shortages to continue to increase into the next decade. The United States Environmental Protection Agency (EPA) plays a critical role in decisions regarding how water resources are used and possibly modified and in developing and enforcing rules to protect water resources and improve water quality.

Historically, EPA has used paper-based maps and aerial photography prints to understand how environmental conditions have changed over time. These analog methods served EPA well in the past but are no longer efficient today.

EPA employs a variety of geospatial tools to complement its standard practices of photogrammetry, which is the art and science of extracting 3D information from photographs and turning them into 2D or 3D models. Together, this matrix allows the EPA to establish a unique, iterative process in its work and to better develop facts that support the enforcement of a case. In some cases, there were questions about jurisdictional wetlands under federal law; for example, Does a specific wetland connect to a navigable waterway? Such information is important for commerce and an understanding of how the wetland has changed over time. Once the EPA embraced the power of remote sensing and digital mapping, it realized those tools can help resolve investigations and provide facts. 

Peter Stokely is an environmental scientist in the EPA's water enforcement division in Washington, DC. "My focus has been [on] helping compile the facts to support enforcement cases for Section 404 of the Clean Water Act [CWA], which is the part that protects our nation's wetlands and streams and rivers from being filled with solid material. We are working to protect the environment," said Stokely. 

Critical questions, such as where federal jurisdictional wetlands are located and if they are being managed in compliance with law, arise in Stokely's work, and it's his responsibility to marry the field components with the data and mapping for fact-finding. With geographic information system (GIS) technology, Stokely looks at current and historical imagery to digitize changes over time.

"You can make a lot of interpretive mistakes by just viewing two-dimensional imagery," Stokely said. "ArcGIS provides the ability to incorporate other geospatial data layers, such as contour lines and digital elevation models, to inform imagery interpretation." 

Historical imagery is useful for more than to solely understand landscapes. To evaluate the historical impacts to a local water resource, the EPA applies tools such as photogrammetry to support advanced spatial analytics. Asking critical questions about an area's past can help guide decisions and point out potential implications for the future. The historical imagery is imperative and, when studying a property subject to pollution, helpful for determining the source and timing of the contamination. The time sequence helps the EPA understand the natural resources and the natural landscape in terms of the Clean Water Act wetland context. 

Fact-finding and answering questions that come up when viewing landscapes is not new to the EPA, but it recently began exploring the possibilities of orthomapping in ArcGIS Pro. 

The goal with orthomapping is to augment the historical information to make better decisions for the future that include efforts to support all EPA's work including the CWA and the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). The CERCLA provides federal funding to clean up uncontrolled or abandoned hazardous-waste sites.

Orthomapping in ArcGIS Pro provides critical support to EPA studies by accurately placing the raw historical photos into the same view with existing datasets and maps. "It's more efficient because . . . you can jump into the process of building a model more quickly this way," Stokely said. 

Before transitioning to ArcGIS Pro, Stokely said his existing methods—to view paper and photographic transparencies on a light table with traditional optical devices—was slow and tedious. 

"The old method [involved manually positioning film or prints using] optical devices . . . you would move your photographs by hand, and they would get out of alignment," said Stokely. "With orthomapping, the ability to view and pan around three-dimensional images on a computer screen is amazing. You know how crisp the imagery can be and then how the three-dimensional image can be so realistic."

In addition to producing more accurate images that are faster to review, aerial photography in a 3D format helps decision-makers see original imagery in a mapping context and identify relevant facts about authenticity.

The updated digital maps do not replace historical data—they enhance it, creating a new level of rigor and analysis. Compiling detailed information about a specific site of interest, at one or multiple different times in history, can be critical to understanding and documenting the site's current state and then examining its future possibilities.

Moving forward, there will likely be continued enforcement actions under the Clean Water Act, as there is an increased need to understand the impacts of climate change and human activities on natural landscapes. ArcGIS Pro provides the EPA with a GIS in a powerful, single desktop application that supports data visualization, analysis, authoritative data maintenance, and more.

Stokely believes that there are more applications for GIS in the future. "There are still things to discover in historical imagery about past pollution events where three-dimensional viewing is helpful," Stokely said.