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.


2 thoughts on “Raster vs Vector in the Swamp

  1. HI!
    Always thought the Dismal Swamp to be the most exciting and scary place (northernmost range for Alligators, has real cottonmouths, and not just the imitation cottonmouths from around Richmond (Northern Water Snake) native of the Richmond Va. area, living in Goochland now. Fan of Lee Berger and the Rising Star Expedition. Anywayyy…
    Would love to see more photos of trees from there, especially giant trees. So….if you take some giant tree photos while you are there, please share em.
    I once took part in archaeology field school at Jordan’s Point Va. (1992 ish). So I guess because of all this, a good photo of a giant tree with a real cottonmouth and an alligator would be just about the coolest thing ever. Unless you get a photo of Bigfoot (aka black bear).
    the crazy old mail man guy Craig Foutz


    • Thanks for your message! Not too many giant trees left in the Dismal- logging in the 19th and 20th centuries really did a number on the old growth forests. Haven’t seen any alligators and I try not to think about them. 🙂


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