Raster vs Vector in the Swamp



Maybe my next project will be archaeology of skiing?  Or, archaeology on skis?

Working through a few ideas from my dissertation here…In GIS and mapping, data comes in two main types:  raster and vector.  Raster data assumes the earth is a continuous surface with various properties mapped as fields in pixels on that surface (Goodchild et al., 2007; Delameter et al., 2012; Weiner 1995).  The elevation information contained in a lidar layer is an example.  The entire surface being modeled, every pixel in the grid, is assigned some value; there can be no ’empty’ pixels. Therefore, “[t]he critical concept for theory is that for raster systems, meaning is independent of boundaries” (Zubrow 1990:70; italics in original).

Vector data is a collection of points, lines or polygons-locations shovel test pits or outlines of islands for example. If the entire surface is assigned some meaning with a raster system, only the objects themselves have meaning in a vector system (Zubrow 1990). For analytical purposes, this means the space between objects simply does not exist in a vector system.

That last bit has become troubling as I try to form coherent thoughts from what I’ve learned about the Swamp landscape during my fieldwork.  As much as we think in vector terms about islands (polygons), artifacts (points), and canals (lines), the Dismal itself is more than a bunch of dots and shapes strewn across a map.  It is, instead, a continuous surface where variables like wetness underfoot have different values in different locations.  Moreover, one does not beam from one island to the next (though that would be handy).  Rather, one steps through gradations of dry and wet terrain.  The wet space between islands not only exists but also is meaningful, emphasizing those islands as good places to build shelters, contributing to the wetlands character of the landscape, and more.

We’ve argued elsewhere maroons were not living their lives entirely on an isolated island, yet we continue to discuss and analyze (artificially?) bounded sites in the Swamp.  What else might we learn about the resistance landscapes of the Dismal if we conceptualized our data as raster of a wetland rather than vectors in a swamp?

Delameter, Paul L., Joseph P. Messina, Ashton M. Shortridge, and Sue C. Grady
 2012 Measuring Geographic Access to Health Care: Raster and Network-based Methods. International Journal of Health Geographics 11(15):1-18. http://www.ij- healthgeographics.com/content/11/1/15.

Goodchild, Michael F.
 2010 Toward Geodesign: Repurposing cartography and GIS? Cartographic Perspectives 66:7-21.

Wiemer, R.
 1995 Another Way to Deal with Maps in Archaeological GIS. In Archaeology and Geographical Information Systems: A European Perspective. Gary Lock and Zoran Stancic, editors, pp. 303- 311. Taylor and Francis, London.

Zubrow, Ezra B.W.
 1990 Contemplating space: A commentary on Theory. In Interpreting Space: GIS and Archaeology.  Kathleen M.S. Allen, Stanton W. Green and Ezra B.W. Zubrow, editors, pp. 67-72. Taylor and Francis, London.


Uneven Landscapes, Uneven Histories


Seen in Ft. Worth

Swampscapes traveled to Ft. Worth, TX, last week for the 2017 Society for Historical Archaeology Conference.  It snowed.  In Texas.  Really.

Together with maroon scholar and University of Florida Phd student Liz Ibarrola, we presented a paper “Uneven Landscapes, Uneven Histories: Maroons in the American Historical Narrative.”  Liz studies the role of maroons in slowing US expansionism in Florida.  We’ve both noticed how the histories of maroons in Virginia and in Florida are given short shrift in common or popular tellings of the US American story.  So, we asked

“are there points in the highlights reel of US history many people carry in their minds that we can connect with in order to demonstrate the importance of marronage in the history of the United States? Can we as archaeologists mobilize these moments where the interconnectedness of marronage and other themes of US history come close to the surface in order to draw Maroon lives out of the margins of history and turn public attention to the contributions of hidden African and African-American people?”

Liz pointed out how the Spanish granted land rights to escaped slaves who helped defend their territory from the British.  Later, during the War of 1812, the British themselves recruited maroons to the fort at Prospect Bluff to defend against the US.  These Maroon settlement were “seen as a very real threat to the regional plantation system” and to Southern slavery.

For the Dismal, I highlighted George Washington’s Dismal Plantation whence two men called Tom and Lewis marooned in the Swamp for many years, and of two Revolutionary War incidents.  The Battle of Great Bridge and Dismal Swamp maroons even make a (very, very brief) appearance in the 2016 version of Roots.

By picking up these threads where maroon history intersects with well-known historical characters and events, we aim to “build deeper, more complex narratives” while also challenging the popular narratives.

“Maroons existed in the hidden and marginalized spaces of the colonial landscape and today, they remain marginalized in the figurative landscape of history. Maroon archaeology, then, has the capacity, and indeed the responsibility, to bring an unfamiliar story to the public.”

I’ll post the full paper over at academia.edu.