Opening Up Archeological Data

Archeology and GIS

Archeology was one of the first social sciences to tap into the power of GIS to map and manage data acquired during excavations. Such systems document the location of finds large and small, the age of the artifacts, and store detailed measurements. The GIS may also contain insights into the people or creatures that might have lived there and then.

While archeologists are keen on finding where relics are buried, they are also called upon to determine if areas are void of such finds. Maps of "archeologically negative" areas are equally important to locate, especially when present day construction is planned.

It's that connection of the mapping of the past and mapping of the present that brings archeological GIS users to demand interoperability. Scientists need to be able to build their maps with the best tools available, then explore them in the context of today's world and today's data. How interesting and enlightening to overlay the locations of finds dating back thousands of years, with today's aerial or satellite imagery, or statewide cadastral data!

At the forefront of this work is Dr. Reiner Goeldner of the Archaeological Heritage Service of the Free State of Saxony, Germany. His is the story of where archeology, GIS and OpenGIS Specifications come together.

A New Law

In 1993 Saxony, the home state of Dresden and Leipzig, passed a new law protecting archaeologically significant places. In particular, archeologists would be required to document both locational and descriptive information. The system would have to be flexible, expandable, provide quick turn around of queries, support state authorities, and be called upon for reference in legal matters. In addition, the system was meant to provide a resource to the scientific community.

In 1994 Dr. Judith Oexle, then the freshly installed director of the Archaeological Heritage Service, decided to develop a GIS as the center of such a system. The project website explains that, "the position or area of a monument [a monument is a preserved archaeologically detectable trace of human life associated with a location] is stored in the spatial data and connected with a data record, which describes the monument. The data record contains among other things the kind of object (e.g. settlement or grave yard) and a time position (e.g. neolithic or bronze age)."

A screen shot of the first system, from 1994/95. Attributes are associated with finds.

In the following few years local, archival data on archeological finds were gathered an entered into the GIS. With a significant increase in building and road construction after reunification of Germany, the system got quite a lot of use. The focus, technically, was in providing simple client software for the staff at the office.

In 1999 the database structure was expanded to hold not only archaeological monuments, but also single find spots (that don't qualify as monuments), excavations and archaeological negative areas. Further additions featured detailed information on all current archaeological activities and enhanced information on finds. Capturing all of this data required reaching out to a variety of sources in different organizations.

The data collection work, while time consuming and tedious, brought definite benefits. Searches of point locations or large areas were possible in real time, and on demand. Monument maps designed to aid in development and planning could be printed out or made available digitally. Archeologists could map finds from a selected time period or map just a specific type of object, something impossible just a few years earlier.

The Database

As of June of 2003 the state's archeology database included:

- approximately 26,000 data records describing more than 21,000 archaeological sites (including more than 13,000 monuments)
- more then 25,000 archaeological activities, about 5,000 of those are excavations
- in 2002 alone, 733 activities were registered, among them 489 excavations, 106 scientific reports and 62 aerial photographs

OpenGIS Web Map Service

The current map rendering: red areas area monuments, orange are single find spots, violet are excavations, and blue are negative areas.

In 2002, the system was ready for both hardware and software upgrades. This included a change to support the OpenGIS Web Map Service (WMS) Specification, a choice that would bring the system into sync with modern Web mapping technology and make the archaeological data useful both within the state's website and on the Internet at large. The WMS version of the website, built on SICAD Geomatics' technology, has been online, via an intranet, since the summer of 2002.

The logic to move to WMS server and client was based on the two typical questions GIS users have: Where do I find base maps? How do I integrate them with my data? The challenges of conversions and the movement of large data sets mean that many organizations keep copies of the same base data. The solution, WMS, as the website notes, "permits the user to load and combine geo data from different sources on the Internet from different manufacturers."

The Archaeological Heritage Service identifies five specific advantages of using WMS compatible software:

• direct on-line access to geodata
• central administration and configuration of the data sources which leads to lower costs
• central, automatic delivery of the Web Mapping Clients (in this case a Java client) over the Intranet, which led to lower software and installation costs
• enhanced "openness"
• the ability to work with other OGC WMS data sources

The Land Surveying Office of Saxony Data serves ortho photos that via its WMS server that can be overlain with archeological information.

In April 2003 the Land Surveying Office of Saxony launched its WMS, also built on SICAD Geomatics' technology, with basic geodata of Saxony (topographic maps of various scales, ATKIS [a Germany wide standard of topographic vector data], and orthophotos). The two groups tested the system over the summer and fall, and on November 10th, made both systems available. Now archeological sites can be easily overlain with orthophotos, providing a better basis for planning and decision making inside government services and opening a new world of possibilities. Due to security concerns the service is currently available only within the state's Wide Area Network, but the plan is to make it publicly available via the Web in 2004.

Serving the Public Sector and Science

ATKIS data from Land Surveying Office of Saxony WMS server, is overlain in a WMS client with monuments provided by Archaeological Heritage Service server.

The forward-looking staff at the Archaeological Heritage Service has put in place a system that serves its needs today and paves the way for the future, as demands change. Perhaps equally importantly, the choices made lay a groundwork that serves the public sector, by providing instant data on where finds may preclude development, and the scientific community with a robust database for research.

The open specifications that make this widespread use possible allow both groups to tease all they can from this data repository in the context of other spatial data, as they see fit.

Images Copyright by the Archaeological Heritage Service of Saxony. Used with permission.

About the Author Adena Schutzberg owns ABS Consulting Group, Inc. She writes about geospatial topics on behalf of the Open GIS Consortium and other clients.