Cyberstaking Archaeological Sites: Using Electronic Marker Systems (EMS) for a Site Datum and Monitoring Station
Robert G. Whitlam
A major issue in effective cultural resource management is the accurate
relocation of archaeological sites for monitoring proposes. The acquisition of
longitudinal environmental data such as changes in vegetation, soil, surface
erosion, and vandalism, are among the long term interests in cultural resource
management monitoring. Effective acquisition of such information in relation to
a specific archaeological site is based upon a stable and secure datum that can
be easily and unambiguously relocated.
The emerging technologies of Electronic Marker Systems (EMS) being employed in the field of underground utilities offers unique applications to archaeological problems. Unlike surface stakes, EMS are durable, passive markers that can be buried in auger holes, test pits, or trenches and have no visible surface presence that can be vandalized or utilized by archaeological looters to locate sites.
The Crowded Underground
How I became aware of EMS technology is an example of the serendipitous nature
of science, technology, and archaeology. As State Archaeologist of Washington I
was asked to speak before a state-wide coordinating council of representatives
from the underground utility industry. I gave my talk about the archaeological
resources of the state and contemporary cultural resource management, then
stayed to listen to other presentations. I thus learned about the current
infrastructure beneath our feet and the EMS technologies that can help to pin
Archaeologists who have conducted pipeline, fiber optic, cable or sewer and water system surveys are probably familiar with how crowded easements and right-of-way can be. Most of us have seen the different colored spray paint dashes on roads, sidewalks, and lawns. Within a single easement, there may be several different power, telephone, and fiber optic cable lines, jockeying for a limited amount of space with adjacent or underlying water or sewer lines. In urban areas, abandoned systems create pickup-stick layers of crosscutting pipes and wires. It is already crowded down there and becoming increasingly more so.
The utilities companies have to address a problem that is common to archaeologists: relocation. Once they have installed the line, they will in the future have to relocate it in order to replace it, repair it, or verify its location for some new construction. Like archaeologists, they rely upon maps, dimensional measurements, and GPS readings, and employ above ground markers and stakes. However, the stakes and above ground markers are often vandalized, removed, or covered over by subsequent construction. There are can also be errors in the maps and GPS readings, and ad hoc construction changes can alter facility placement that is not reflected in the as-built drawings.
Electronic Marker Systems
In order to meet the need to relocate critical underground resources there are
numerous types of locators. Most archaeologists are familiar with metal
detectors or magnetic locators that can be used to locate buried metal objects.
Such locators are used to locate facilities such as metal valves, junction
boxes, and metal pipes. However, because they react to ferrous objects, any
number of false positives can be encountered--bottle caps, nails,
coins--instead of the target.
EMS offers an elegant solution, consisting of two parts: a portable locator and a buried antenna. The locator looks much like a standard metal detector. It is worn over the shoulder and operates on standard C batteries. It attaches to a shaft that has a disk that transmits the signal to the buried marker. The basis of EMS technology is that the locator transmits a pulse at a given frequency to which the buried marker is specifically tuned. In effect, the buried marker is preset for a specific signal and will only respond to that frequency. The markers are passive antennas with no internal power source and are made with polyethylene shells to be impervious to the extremes of chemicals, temperatures, and mineral conditions typically found in undergound environments.
There are four types of markers: Near-Surface, Ball, Mini, and Full Range. These reflect the specific needs in the underground utility industry and have different distance requirements for signal reception. Depending upon type of marker and depth of burial the range is between 1 to 2 m.
Cyberstaking Archaeological Sites
I was intrigued by the presentation of EMS technology, made by representatives
of 3M Corporation. 3M markets this technology under the tradename
ScotchMarkTMElectronic Marker System. Having used
wooden stakes, iron rebar, marked trees, and nails in posts as archaeological
datum points and having experienced the subsequent--often frustrating and
futile--search to relocate the site datum, I thought EMS may offer a very
useful tool to archaeology.
To pursue this goal, I developed and submitted a proposal to the National Center for Preservation Technology and Training (NCTT), and was successful in receiving funding. The project, titled Cyberstaking Archaeological Sites, involved implanting EMS markers at a variety of archaeological site types in different environments in Washington State, with varying and ongoing natural and human impacts. The objective of the project was to assess the value of EMS technology for archaeological applications. Washington State has diverse environments ranging from coastal maritime forests to subalpine and alpine environments, desert, riverine, and open prairie environments. There are also a variety of site types in these environments: lithic scatters, village sites, shell middens, quarries, and rockshelters that are subject to a range of natural and human impacts.
I was able to enlist the interest and participation of archaeologists that I work with routinely, and this provided the project with a variable range of agency activities, survey techniques, experience, and training. 3M Corporation provided me with a locator, sample markers, and technical assistance.
Interested archaeologists were invited to meet, observe a sample demonstration of the cyberstakes and locator, brainstorm the possibilities of EMS application in archaeology, and then establish procedures for implanting the markers. Some guidelines for the project were established. The participants decided that the sites selected should reflect the environmental and archaeological diversity of the area, should be easily accessible, and could thus be monitored by archaeologists throughout the year. No known burial sites would be marked. Agreeing to stress a conservation ethic, markers were to be implanted only outside of site boundaries or in site areas that were already disturbed.
EMS application was seen as potentially useful for archaeology in the following areas: (1) relocation of sites in survey and archaeological site inventory, (2) relocation of excavation and test units, (3) archaeological site monitoring and longitudinal studies to monitor erosion, vegetation, soil changes, or other impacts, (4) archaeological site protection by enclosing the site in a cyberpolygon which serves as a buffer for avoidance, (5) use by researchers in other disciplines who also need to establish relocatable datums for longitudinal studies parallel to those of archaeologists'.
Those participating generated a list of more than 50 suitable sites. The orange/telephone marker was selected, and 44 near-surface markers and 76 ball markers were distributed to the participants who implanted the markers in the sites in the course of their field activities--auger testing, test pit excavation, or site datum establishment--during the winter, spring, and summer of 1997 (Figures 1 and 2). Rather than implanting a single EMS marker at a site they used multiple markers, establishing either a protective bubble around the site, a cyberline or cybertransect parallel to the site, or placing them in the corner of an excavation unit prior to backfilling.
Figure 1: Jim Henderson planting a cyberstake at an archaeological site in the Columbia Gorge.
Figure 2: View of a cyberstake or ball marker in auger hole.
Site Revisits and EMS Relocation
During summer and early fall 1997 I arranged with the participating
archaeologists to revisit EMS-marked sites. Since I had not participated in the
markings, I would be relocating the implanted marker based solely upon recorded
information. The objective was to assess the effectiveness of the procedure,
create an efficient site relocation methodology, and finalize guidelines for
EMS use in archaeology.
The typical revisit was done in the company of the archaeologist that had implanted the marker. Using a generalized description of the area or using a site map or GPS reading I would employ the locator and conduct sweeping transects of the site area to relocate the cyberstakes, striving to replicate the existing information that the typical archaeologist would be using.
There is a learning curve to using the locator, and over the course of the field season I was able to develop skills in fine-tuning the locator to locate the cyberstake more quickly and precisely. The locator has a tuning scale much like a vehicle fuel or oil pressure gauge with a range from 0 (low) to 10 (high) sensitivity to the marker. The locator also emits an audible tone as it locates a buried marker. By setting the locator at maximum sensitivity one can quickly scan transects to locate the general area of the marker. This general area, given the type of marker and depth of burial, is about 1 to 2 m in diameter. By fine tuning the sensitivity dial one can zero in on the exact location of the marker (Figures 3 and 4).
Figure 3: Rick Bailey, BLM archaeologist, monitoring coastal erosion with cyberstake in the San Juan Islands.
Figure 4: Bob Mierendorf, North Cascades part archaeologist, relocating cyberstake in Northwest coastal forest.
Once I mastered the technique I was able to relocate the markers in under two minutes, given a general area of less than 10 m on a side. I was also able to locate the markers in areas that were heavily vegetated without having to disturb the vegetation or excavate.
These relocation efforts were successful with only two exceptions. In one case we received a weak signal which we attributed to sediments deposited by spring flooding that may have buried the marker beyond the range locator. In the second case the ball marker initially responded to the locator but did not respond subsequently. We excavated and retrieved the marker, shook it and then received a signal. Discussing this problem with 3M representatives it was suggested that the internal antenna may have been stuck at an angle that would not properly reflect back the locator's signal.
In both cases, there is a solution to these problems. All markers were implanted by the archaeologists without the aid of the locator. However in areas where heavy deposition or erosion is expected the markers should be planted at different depths. To assure a strong signal and that the marker is functioning properly the archaeologist should check them with a locator at the time of burial. This will establish the baseline condition that markers are functioning adequately at the time of implant.
Recommended Guidelines and Suggested Protocols
In order to assess the value of EMS application to archaeological sites and
cultural resource management problems it is important to recognize it as
another tool for the archaeologist to more easily, efficiently, and reliably
relocate a stable datum point or line. EMS markers provide an important
supplement and enhancement to field maps, GPS readings, photographs, and
professional site documentation. Markers should not, however, be seen as a
substitute for an adherence to professional site documentation standards.
Use of an EMS marker is particularly appropriate in a circumstance where one does not want to leave any visible stake or marking that would identify a site's location, or be observed or vandalized. It is also appropriate for sites that have or will have a heavy vegetation cover and in circumstances when the archaeologist does not want to cause further vegetative or soil disturbances to a site during later relocation or monitoring activities.
EMS markers are very useful when other professional or agency staff need to quickly relocate site boundaries or "no entry zones" in emergency situations in the absence of the recording archaeologist. The locator can be express mailed to the on-site ranger or manager to relocate definitively the protective cyberpolygon established by the archaeologist around the site. Since EMS markers are widely used in the underground utilities industry most excavators and contractors will recognize and respect the markers as protective warning signals indicating areas not to be disturbed.
Finally, the use of EMS markers makes an important statement of the archaeologist's or the agency's commitment to return to monitor the site, reflecting a very active form of cultural resource management.
The following guidelines reflect our experience to date:
(1) Planning is critical in using EMS markers. While it is easy to carry a handful of near-surface markers in one's coat pocket or ball markers in one's field pack, it is important to identify one's cyberstaking goals beforehand. Will it establish a stable photo monitoring point or a grid line, create a datum to measure erosion or human impacts, mark an important site feature or artifact, or create a cyberpolygon with a buffer around the site? Those goals and the site's location, vegetation, sediments, and use can influence the number and type of markers to be implanted.
(2) Establish beforehand your ethic of site disturbance in the placing of markers. In our efforts we purposefully tried to avoid disturbing site sediments. EMS markers work well with a conservation ethic of leave no trace, leaving no visible stakes, ribbons, or iron rebar at the site. For future monitoring neither the soils nor the vegetation need be disturbed. By taking electronic readings and photos one may leave only footprints during monitoring.
(3) Plan to use more than one EMS marker. While at some sites we implanted only one it is preferrable to implant multiple markers to establish a more useful grid. By having multiple markers it increases the ease of relocation, and in the event of loss to erosion or malfunction, there are other markers to recover.
(4) If possible, test with the locator and confirm the strength of the signal from the EMS marker at the time of implant, to avoid malfunction. This procedure also serves as a training opportunity for the archaeologists in the use of the locator under controlled conditions. While the locator is the most expensive component of the system, for a large land managing agency it is possible to have one in a central locale for different archaeologists to check out and use as needed. We plan on keeping a unit in our office for such use.
(5) Incorporate the EMS marker location information and EMS data into the permanent site records. Include descriptions of the placement of the EMS markers and specify the type of marker (ball or near-surface) along with the APWA frequency (orange/telephone). Other information such as depth of burial and initial implanting conditions may be useful for future relocation and monitoring efforts.
Cyberstaking or the use of EMS markers addresses a national need to develop and
implement an efficient, non-visible, and easily relocatable datum point or grid
line for archaeological sites. EMS markers are widely used in other fields such
as the underground utilities market. The application of EMS markers to cultural
resource management issues meets a variety of research, and conservation needs.
This project was supported by the National Center for Preservation Technology
and Training (NCPTT), with additional assistance provided by the 3M
Corporation. I greatly benefited from the advice and support of Mark Gilberg,
of NCPTT and Jacque Washburn, Mike Hall, and Laura Nereng of 3M.
I also appreciate the support and participation of the following archaeologists in the field: Rick Bailey, Bureau of Land Management-Spokane District, Alex Bourdeau, U.S. Fish & Wildlife Service, Greg Cleveland, Yakama Indian Nation, Paul Gleeson and Kirstie Haertel, Olympic National Park, Bret Lenz and Kathy Kiefer, Grant County Public Utility District No. 2, Rick McClure, Gifford Pinchot National Forest, Dan Meatte, Washington State Parks and Recreation Commission, Bob Mierendorf, North Cascades National Park, Fennelle Miller, Washington State Department of Natural Resources.
Robert G. Whitlam is state archaeologist of Washington.