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North Carolina's State Historic Preservation Office is integrating its historic properties data into a Geographic Information Systems (GIS) platform.

Users can now uncover data on National Register, local landmark, and survey properties within map layers.

This data can also be used to show how historic preservation tax credits are being used across North Carolina.

These presentations by Michael Southern and Andrew Edmonds highlight how the system works and what we can learn about tax credit use from the presented data.

Presentation Notes

by Michael Southern, NC Historic Preservation Office

Slide 1. The first efforts at systematic historic property surveys began in the late 1960s, and the first meeting of the National Register Advisory Committee took place in the fall of 1969, 41 years ago this month. Since then, North Carolina has seen:

•  over 2700 entries in the National Register of Historic Places, of which about 500 are historic districts encompassing thousands of historic properties,
• over 4200 Study List entries for potential nomination to the National Register
• over 1,000 properties and districts determined eligible for the National Register in environmental review activities,
• over 1200 locally designated landmarks and over 100 locally designated historic districts,  and
• uncounted thousands of properties recorded in field surveys undertaken over the past 41 years.

This body of knowledge of the state's cultural inheritance has been gathered, and continues to be gathered, by many score diligent historians assisted by countless citizens and property owners who have contributed information to these surveys.  

While many of our county and municipal surveys have been published, many of those are long out of print, and most of that knowledge has resided only in one-of-a-kind paper survey files and marked on one-of-a-kind paper maps located at the Preservation Office.

Slide 2  Over the past four years the HPO has been rushing to join the late 20^th century, as I like to say, implementing GIS (which stands for geographic information system) to get a better handle on this data and make it more widely available for planning and research.

GIS software is complex and expensive, and it's not something that most of us as individuals would acquire. But most government agencies and many environmental firms have it in one form or another. Anyone with GIS software can generate and share spatial data with anyone else who has it, either by giving others copies of the actual data files or by delivering the data over the web with a mapping service.  As we will see, it is also possible to view such web mapping services with free software tools such as Google Earth and ArcGIS Explorer.  And ultimately, the data can be displayed on a website with only a browser needed.

In early 2009 I advertised for a GIS intern to help us map places, and I was lucky to attract two very talented people looking for part-time work, and so I was able to get both.  Though they have overlapping skills, Heather Mounts specializes in the complex architecture of a full service, multi-user GIS system - which we now have at the HPO thanks to her -- and for creating web services to deliver the data to the outside world.  Andy Edmonds is a master at data creation, evaluation, and presentation.  We've also been lucky to have Sam Franklin as an intern to help with data mapping, and Jessica Dockery on our staff has contributed as well.

Slide 3  If you haven't yet been introduced to GIS, it works on the principal of stacked-up layers which may be viewed simultaneously but which may be coming in from many different locations - from any computer on a network or pulled in from multiple sites on the web. Layers may be picture data such as maps or aerial photos, or vector data created to represent anything from wetlands and species habitats to utility lines and school districts to historic buildings and district boundaries. Layers can added or removed from a map and be turned on and off and labeled depending on what you want to see at what scale. 

Slide 4   The symbology of the points and lines created to represent features can be easily changed. For our purposes here is our symbology. Blue for NR, Green for SL, Orange DOEs, and so forth.

Slide 5  Where do the points and boundaries come from? There isn't a magic button that creates them, and we aren't going to drive the 100,000 miles of roads in North Carolina with a GPS unit to map everything.

We start with our old paper maps. We have scanned and georeferenced all 1500 of the marked-up USGS maps created in our survey and National Register programs.  

Slide 6  We assign a GIS point to points marked on the map and enter the site number. Our point layer is linked to our survey index with the site numbers, and that give us the property name which is included in the label with the site number.

Slide 7  Other tools help us check things out. High resolution aerials pulled in off the web from NC OneMap help us confirm locations or even whether something still exists.

Slide 8   Google Earth and Birdseye tools don't cover the entire state, but often put us on the ground in front of a building to compare with ground survey photographs.

Slide 9   Boundaries for National Register nominations are usually based all or in part on parcels,  but sometimes on natural or manmade features which can be traced from the aerials or USGS map.  

Slide 10   Parcels are of particular importance when drawing a district boundary. Older districts defined without parcels are much more difficult to draw, and often require a little eyeball work.  Many early individual nominations did not have defined boundaries, and it isn't possible to draw a boundary.  

Slide 11  When you've done this for 2700 National Register listings and zoom out to see the whole state, this is what the distribution looks like.

Slide 12   When we create a point, we enter only limited information about it.  We can link the point to the much more detailed record in the survey database with the site number.

Slide 13  and for nominations, we also include a link to a PDF of the nomination on the web.  We have PDFs posted for only about 200 of our most recent listings, but the Park Service is in the process of making PDFs of all of our old nominations, and we hope to have all linked to our GIS in the first part of next year.  We haven't settled on a system for linking photos to all features, but we're working on that.

Slide 14  This map shows the status of our progress in mapping designated and surveyed properties and districts. Several of the western counties aren't indexed, and we can't finish the mapping without the actual files, which are in the western office.

Slide 15  We're also mapping locally designated landmarks and districts, and we will be contacting commissions to compare notes.  GIS helps us visualize the relationship between National Register and local programs. In Chapel Hill we have three National Register districts (blue shading) overlapping with local districts (pink outlines) with different names and boundaries. And we wonder why the public gets confused about preservation programs.

Slide 16  One of the most important uses of GIS is in environmental review. The red shape is the study area for a proposed freeway in southern Wake County, drawn by the engineers for the study.  The area covers parts of 9 quads, some of which we have two or three versions, each with different data. The traditional method of identifying designated or surveyed properties in the area by examining the paper maps and noting site numbers to compare against the index would probably take several hours, maybe a day or more.

Slide 17  With GIS, you can identify places within the area

Slide 18  and generate a simple list a couple of minutes.

Slide 19  GIS can also help with general research when you have a populated survey database, which I have to emphasize that we have only for four counties with recent survey updates and for districts listed since about 2007.  This map of Forsyth County shows us the distribution of designated places countywide and surveyed sites in rural Forsyth. The black dots show places surveyed by Gwynne Taylor in 1980 that were gone when Heather Fearnbach did her recent survey update, an attrition rate of about 30%.  We can join the points to Heather's detailed survey database and start to see other things.

Slide 20  The highlighted points show the distribution of all the places with Log in the construction field, and it would be easy to generate a report including any of the data in the survey database.

Slide 21  This shows the distribution of the Queen Anne style. The same could be done with architect or design source, condition and integrity, date range, and so forth combined in any combinations.

Slide 22  For recent historic districts that made use of the database such as the Ardmore-Westbrook Historic District in Wilmington, we can show such things as contributing and noncontributing properties,

Slide 23  the distribution of style groups - here green is craftsman bungalow,

Slide 24  and the distribution of artificial siding - red is vinyl and gold is aluminum.  These are just examples.

Slide 25  We can't do those sorts of things for older districts until their surveys are updated and the databases populated. But Andy has devised a system for capturing the parcels within older districts and identifying the contributing status from the district maps in the files. And this leads us to Andy's special case study joining GIS data to the preservation tax credit database.