GISday is an international observance that is designed to make people aware of the possible uses of geographic information systems. Various events are held around the world to highlight GIS projects.

ESRI LogoBegun in 1999 by ERSI, a leader in GIS development, this day is used as a time to help people learn about geography and the interconnectedness of our world.

GIS Day LogoCentral Pennsylvania GIS Day is held at the Midtown Campus of Harrisburg Area Community College and is a joint venture of HACC and the commonwealth agencies that use GIS. This FREE event is open to the public from 10:00AM – 7:00PM. The theme this year is GIS: The Next Generation. Presentations will look at new ways that GIS is being used in business and government, and include both technical sessions and project “show-and-tell” sessions. Topics include using online, mobile, and 3D tools; where to find publicly accessible data; and the use of GIS in planning, surveying, and tracking change for subjects as varied as forest fires, abandoned wells, archaeological sites, bike trails, land trusts, and parish populations.  A full schedule is available on the website.  But mostly the day provides a time for GIS users to get together and share ideas and for non-GIS users to learn about its possibilities.

So what is this GIS thing and why should you as a preservationist care?

GIS, or Geographic Information System, is basically intelligent maps – maps with data behind them. You can store information about locations on your map. You can do analyses of relationships between places. You can compare various “layers” of data and see what they have in common. It allows you to look at many kinds of data spatially, both in two dimensions and in three – and even through time. GIS adds the spatial dimension to data.

Today, GIS is everywhere! It is used for everything from marketing to disaster response.

When your smart phone tells you what restaurants are near your location, it is using GIS.

When you call 911 and they send help via the shortest route, they are using GIS.

CRGIS LogoWhen you look for historic resources in your area using our Cultural Resources GIS, commonly known as CRGIS, you are using GIS.

The BHP maintains the state’s historic and archaeological resource information in a GIS that is made available to the public at our CRGIS. This system has the two basic functions of searching for resources spatially (on the maps) or thematically (through the database).

Beyond this basic searching function, there are two primary uses of GIS in archaeology. One is to map the relationships among artifacts within an excavation; the other is to analyze the distribution of sites across larger landscapes. We archaeologists have basically been doing geo-spatial analysis for decades, using multiple maps and overlays.

GIS provides the tools to do these analyses much more quickly and accurately, after entering data only once.

When artifact and feature data is stored in a GIS, you can produce basic maps of the site in 2 or 3 dimensions, just as you could with paper or static computer mapping techniques. But GIS gives you the ability to filter the mapping for certain artifact types (without redrawing anything) and statistically analyze their distributions, or to look for correlations between artifact types and/or features.

One of the talks at Central Pennsylvania GIS Day will focus on the use of GIS to map the World War II POW camp at Michaux State Forest by Dr. Maria Bruno and her students from Dickinson College. You can come hear this paper at 4:00pm or read more about the project on their blog.

The same can be said for site distribution. One of the primary uses of GIS is developing predictive models for site locations. Using multiple layers of environmental data, we can analyze known site locations to determine what factors they have in common that may have led to their choice as habitation sites and then look for other parts of the landscape that have similar conditions. This is a very powerful planning tool both for archaeologists who are looking for sites to dig and for planners who are trying to avoid impacting sites. BHP and PennDOT have contracted a project to develop statewide predictive models for prehistoric site locations that should be available on the CRGIS in about 2 years.

For examples of all of these uses and more, I recommend visiting ESRI’s GIS for Archaeology section.

Historians also use GIS to help show change through time. Overlaying historic maps allows you to understand the growth of an area, such as the Smithsonian mapping comparing New York City of 1836 to today. GIS can also be used to help understand historic events, such as the Battle of Gettysburg.  The Civil War Trust uses GIS and animation to present major battles, both on line and in apps you can carry with you as you visit the battlefields.

GIS can also be used as a research tool when trying to locate information on a given property. Many cities and counties have digitized their property records and made them available online. The City of Philadelphia has digitized and geo-referenced its extensive photo archive so you can look at a map and see what photos they have in that area.

These are only a few examples of the resources available through GIS. Search the web and have fun! Happy GIS DAY!