Imagine a catastrophic event that damages thousands of structures and other important features – sometimes wiping out entire towns. Where is the documentation for what existed? What is important, and what should be replaced? This dilemma is even more serious when the disaster occurs in an area of historic importance, where rebuilding cultural resources with historical integrity is paramount. 

Geospatial data in the form of maps, coordinates, descriptions, models, and large-format photographs are highly useful for documenting historic features of all kinds, and the digital format makes sharing, viewing and analyzing the information accessible to everyone.


Historic Preservation at a National Level

Historic preservation programs administered by the U.S. National Park Service (NPS) include the Historic American Buildings Survey (HABS), the Historic American Engineering Record (HAER), and the Historic American Landscapes Survey (HALS). HABS was founded in 1933 to document irreplaceable architectural heritage. Beginning in 1969, HAER focused on documenting engineering and industry, such as bridges, canals and ships. More recently in 2000, HALS was established to record important landscape features ranging from large parks to gardens. These archives are kept at the Library of Congress in Washington, D.C.

The National Historic Preservation Act of 1966 forms the basis of the rules that protect historic properties today. It creates a framework for evaluating historic places using certain criteria to determine whether it is worthy of protection. The National Register of Historic Places, maintained and stored at the National Park Service in Washington, D.C., is the official list of items dating back to pre-Columbian times that meet the requirements. 

Within the National Historic Preservation Act, Section 106 plays the extremely important role of requiring federal agencies to review how any federal activity impacts historic resources and how potential damage will be mitigated. Since most large construction and development projects are at least partially funded by federal agencies, Section 106 rules are frequently invoked. Federal Emergency Management Agency (FEMA) projects involving demolition and rebuilding of damaged properties following disasters are directly impacted by Section 106.

“The Cultural Resource GIS Facility (CRGIS) is the only department in the NPS dedicated to using GIS/GPS for preservation of cultural resources, so we work with lots of different groups at federal, state, local and tribal levels,” says Deidre McCarthy, chief, Cultural Resource GIS Facility. “CRGIS documentation doesn’t necessarily go to the Library of Congress unless it’s part of a HABS/HAER/HALS report; however, it is used during Section 106 reviews and at individual sites to support many types of planning, maintenance and restoration efforts.”


Preparing Before a Disaster

The value of comprehensive documentation of cultural resources does not always receive the attention it deserves until it is too late. This fact was clear in the aftermath of Hurricane Katrina in 2005, which devastated the historic Lower 9th Ward of New Orleans. The subsequent work done by CRGIS and FEMA created a groundbreaking survey strategy, which includes a data dictionary to maintain consistency and incorporates various types of geospatial technology. This process helped identify and document features of historic significance along the Gulf Coast, and for the first time, provided FEMA with a complete digital database to use for Section 106 mitigation efforts. 

“A succession of major hurricanes – Katrina in 2005, Wilma in 2005, Sandy in 2012 – created the opportunity for us to design and test new strategies for recording and sharing geospatial information,” McCarthy explains. “Particularly in New Orleans, which is an iconic place for cultural resources, FEMA looked a lot more closely at documentation to help comply with Section 106. The attention these disasters received really brought to the forefront that we need to be mindful of cultural resources, and better documentation helped facilitate the mitigation of loss during the rebuilding and restoration process.”

While a typical surveyor creates topography, detailed maps and measurements of properties, the goal of CRGIS is to document things – all kinds of things. Using GPS and historical maps, field technicians compare the actual landscape with available records and make note of where historic features should be. They map everything from markers on a battlefield to trees in a landscape and old headstones in cemeteries. Mapping-grade GPS provides +/- 1-meter accuracy that is adequate for this purpose. The results go into multiple databases, such as an NPS inventory or state historic preservation office inventory of historic places.


Geospatial Technology Impacts Preservation

Early efforts of historic documentation included drawings and photographs. These were usually undertaken by interested individuals rather than government agencies, so results were not comprehensive and did not meet standard specifications for documentation. Improvements in geospatial technology, such as LiDAR, digital photography and 3D modeling, make the documentation of historic sites more accurate and consistent today.

“Advanced LiDAR technology provides a significant improvement in our ability to pick out surface features that may be hidden under vegetation and even underground,” says McCarthy. “By overlaying a historic map over the current landscape, it helps us figure out what is left. We also make use of 3D modeling to help visualize the data that are collected, and handheld GPS speeds up our field work and makes our data collection more accurate.”

Data standardization and web-based platforms allow information to be shared quickly and presented in user-friendly ways, such as story maps. “To illustrate exactly why it is important to have things documented before disasters, CRGIS created a story map for Hurricanes Irma and Maria,” McCarthy says. “The story map shows the paths of the hurricanes, the locations of resources documented by the HABS/HAER/HALS and it shows what is left of those resources after the hurricanes. Resources documented by HABS/HAER/HALS have associated measured drawings, histories and photos that are stored at the Library of Congress. The story map links to all of the documentation that exists, and in some cases, that is all that is left.”


The Future of Historic Preservation

As our built environment expands to meet the needs of the growing population and natural disasters continue to destroy vulnerable areas of the country, the value of accurate data describing historic resources is growing. Advances in geospatial technology, such as LiDAR and 3D modeling, allow preservationists to thoroughly document all kinds of sites to maintain an accurate record and support restoration when appropriate.

Stable funding and regulations are key to federal, state and local agencies being proactive in documenting historic resources before damage is done, which is preferable to being reactive after a disaster. The HABS/HAER/HALS programs are mentioned specifically in the National Historic Preservation Act so they cannot easily be eliminated; however, funding can be unpredictable because Congress has authority over the budget. Also, fewer regulations and less governmental oversight can reduce legal protection of cultural resources. 

“Creating documentation before structures and other artifacts are gone, and making this data available to everyone who needs the information, are our primary goals,” says McCarthy. “To achieve this, we focus on developing close relationships with related agencies and preservation groups, creating useful data standards and building an efficient framework so we can exchange data quickly.”