| Home | Portfolio | Resume | Photos |
Jim Kompanek
Introduction
Between 100 BC and 500 AD, the Newark Earthworks were the largest geometric mounds constructed by the Hopewell people. The two largest remaining portions of the earthworks include a circle, which encompass approximately 20 acres, and the octagon which contains over 50 acres. Unfortunately, through time much of the mound complex has been lost due to erosion and development, with only two surviving segments (Figures 1-4), one to the west which provides obstacles to a modern golf course, and to the east which is within the confines of a state park. Smaller, isolated segments are visible throughout the city in vacant lots and between property lines. Luckily, the earthworks were surveyed multiple times, for various purposes, in the eighteenth century. An in-depth discussion of the earthworks is available at the Ohio Historical Society website at: http://www.ohiohistory.org/places/newarkearthworks/pdf/ (Ohio Historical Society 2003).
Figures 1 and 2. Nineteenth century schematic maps of the Newark Earthworks (Squier and Davis 1848; Wyrick 1860 as adapted from Ohio Historical Society 2003).
Figures 3 and 4. Modern DOQQ of Newark, Ohio (left) and Modern DOQQ of Newark, Ohio with a roughly digitized earthwork boundaries based on historic maps.
Map Design
The goal of this project was the map both the extant (existing) remnants of the mound complex as well as the likely location of the destroyed portions (Figure 5). The inferred location of the destroyed earthworks based upon a georeferenced historic map was the unknown for this project, with the probability of location acting as the data uncertainty.
The resulting map was created by georeferencing the historic Squier and Davis (1846) survey map (Figure 6) of the earthworks. This map was georeferenced using an affine transformation which used the remaining portion of the earthworks as control points. It would have been preferable to use additional control points (preferably near the corners of the historic map) but this was not possible. Based on a comparison between the modern DOQQ and the historic map, the locations of Raccoon Creek and South Fork appear to be somewhat stylized on the historic map. The distance between the remaining circular enclosure to the southeast of the complex and the confluence of Raccoon Creek and South Fork were also significantly different between the modern and historic maps. It seems likely that Squier & Davis may have roughly sketched in the hydrologic features for general reference. When comparing the modern DOQ against the historic map, it also appears that the Ohio Canal likely served as the location of what is now Union Street. Also, the "Road to Newark" indicated on the historic map may indicate the location of modern Main Street. Nevertheless, even though these historic cultural features may indicate the location of modern features, it is still unclear if this the case; as such, only the extant mounds were used as control points.
Because the georeference control points were clustered around the extant portions of the mounds, the underlying theory behind this project was that the confidence in the georeferencing decreased as distance increased from the existing mounds. Furthermore, a second theory presumes that the confidence in destroyed earthwork location also decrease as the distance increased from the georeferenced mound locations. A simple equation was used to weigh the likelihood of a mound being present based upon the distance from the extant mounds and distance from the georeferenced locations (up to 100 m).
Although, all of the georeferencing was based upon a 1:4,800 digital orthophoto, I chose to use the black and white DOQQ (1:12,000) as the background to the map. The color orthophoto was obtained through sources other than the USGS and contained numerous patches of cloud cover. The color map seemed unnecessary and even cluttered the data frame with a wide range of colors. To provide a reference within the orthophoto, a street map (obtained from seamless.usgs.gov) was overlaid on top of it and symbolized based upon the significance of the road. Primary roads within the vicinity of the earthworks were labeled using a gray halo for readability. Unfortunately, the road layer was digitized based off of the 1:24,000 Digital Raster Graphic (DRG) which also predated the DOQQ by a number of years; as such, there were some alignment errors between the road layer and the DOQQ. In general, I attempted to use color schemes which were similar to the gray hues visible in the orthophoto. This included both variations in blue, as well as other light colors such as purple and yellow.
Surrounding the extant earthwork locations are a series of buffer rings at 100 m increments. These rings (which were converted to raster) were used to weigh the probability of the predicted mound locations. Each ring was assigned a value which gradually decreased as the distance increased. I chose to include these rings as a reference point to allow the map viewer to get a better idea how the data was generated.
The uncertainty of the georeferenced earthwork locations were portrayed using a stretched classification in the blue hue. The darkest blue was used for the extant portions of the mounds and a lighter variation was used for the boundaries as indicated on the georeferenced map. The probability portion of the map was created in a similar manner as the extant buffer. Buffer lines were generated (and converted to raster) surrounding the predicted locations in 10 m increments up 100 m. Each of these buffers was assigned a value which decreased the further away it was from the georeferenced location.
A secondary data frame was also included which showed the location of Licking County within Ohio, as well surrounding states. This was included to provide reference for those not familiar with the counties of Ohio.
Figure 5. Probable location of destroyed Native American Mounds in Licking County, Ohio (click on image for full size pdf file).
Figure 6. Earliest survey of the Newark Earthworks by Squier & Davis in 1837 (published 1846). Click on image for full size map.
Critique and Conclusion
I believe the map does an acceptable job at portraying the likely location of the destroyed portions of the Newark Earthworks. Ideally, I would have liked to have done some additional work on the project. As previously mentioned, the complex was mapped multiple times in the 19th century (see Figures 1 and 2). The Squier & Davis and Wyrick maps were somewhat different in how the portrayed the northeastern portions of the complex. It would have been nice to georeference and digitize the Wyrick (Ohio Historical Society 2003) maps and incorporate it into the project, but unfortunately, I was unable to find a copy of the Wyrick maps at a high enough resolution to allow for georeferencing. In addition, even between the 1830's and 1860's a significant amount of historic disturbance had occurred (see Figures 1 and 2). It would have been interesting to model this disturbance..
According to the Ohio Department of Transportation Office of Aerial Engineering (Figure 7) numerous aerial photos are available within the vicinity of the earthworks. These photos were taken during flights between 1952 and 1995. These images would have been very valuable when comparing the disturbance caused by historic growth and could provided a timeline for destruction between the 1830's and today. The earliest flight dates were in 1952 and were at such a scale, they may have provided better georeference control points, as much of the growth in the area occurred after the 1960's. It was generally too cost prohibitive to actually order any of the aerial imagery.
In addition, a thorough literature review would have been beneficial, as it is likely that archaeological investigations were conducted throughout the city, which may have included remote sensing. These investigations may have offered some insight into other potential control points for georeferencing. Ideally too, I would like to have taken a GPSr to some of the known remnants of the earthworks scattered throughout the city for additional control points.
Figure 7. Available aerial photography within vicinity of the earthworks.
References
Ohio Historical Society
2003 Historic Site Management Plan for Newark Earthworks State Memorial. Ohio Historical Society, Columbus Ohio.
Squier, E.G. and E.H. Davis
1848 Ancient Monuments of the Mississippi Valley. Contribution to Knowledge Series, Smithsonian Institute, Washington, DC.
This document is published in fulfillment of an assignment by a student enrolled in an educational offering of The Pennsylvania State University. The student, named above, retains all rights to the document and responsibility for its accuracy and originality.
