Building the Salem Witchcraft GIS

Digitizing the Upham Map

B. Problems with the Upham Source Material

Many problems with the source material present themselves:

  • The map was drawn nearly 200 years after the period it purports to represent.
  • We have no details about how it was surveyed, or about how many of the historical sites were placed.
  • The map scale (1 inch to the mile, or 1:63360) and the degree of feature generalization guarantees that locational accuracy will be low.
  • Our copy of the map is a reprint many generations removed from the manuscript. The process of duplication has undoubtedly introduced distortions into the drawing, which will result in error when trying to georefences the image.

With such uncertainly in the source material, there is little reason to place a high degree of faith in the geographic accuracy of the document, or to believe that we could produce a highly accurate overlay of Upham's drawing over contemporary real-world Salem. Precise positional detail about the location of most of the sites depicted by Upham is impossible to achieve.

Nonetheless, W.P. Upham's map represents one of the best starting points (indeed the only starting point we have) to make educated guesses about the spatial organization of Salem Village and its environs in 1692. Several sites important to the drama still exist, and most of these are pinpointed on Upham's map. We decided to pursue the project of digitizing Upham's map, using GIS software, and accepting the factor of the unknown that is necessarily attached to it. By digitizing the map and creating an Historical Salem GIS, we hope to accomplish several things:

  • Provide a visual interface to other documentation in the project.
  • Provide a visual account of the spread of accusations and their retrenchment.
  • Begin a set of base historical data from which to grow.
  • Encourage other cultural historians to make use of geographic analysis and representations to study the past.
In time more accurate placement of some of these sites may be possible. We hope that our work will provide a place to begin.