CUR - The Council on Undergraduate Research

Horizontal Positional Accuracy Assessment of 7.5’ Digital Geologic Maps of Part of the Nashville Dome, Central Tennessee

Meredeth Bryson, Dr. Mark Abolins, Geosciences Department, Middle Tennessee State University, 1301 E Main St, Murfreesboro, TN, 37132

I seek to better-understand the horizontal positional accuracy of 7.5’ digital geologic maps in general.  For example, it has been asserted that the positional accuracy of well-located contacts on some digital 7.5’ geologic maps exceeds 15 m.  In this project, I quantitatively assessed the horizontal positional accuracy of digital geologic maps.  To accomplish this, I began by georeferencing 48 published 7.5’ quadrangle geologic maps of Central Tennessee using the ArcGIS program. I was provided with scanned geologic maps.  For each scanned map, I matched 10 marked intersections of latitude and longitude with the corresponding points on a USGS 7.5.’ digital raster graphic (DRG).  I then applied an affine transformation to the scanned geologic map.  The mean RMS horizontal positional error was 5.5 m, with a range of 3.1-9.4 m. This could be due to distortions in the scanned maps, and it could be due to human error in assigning matching points. Results will be used in ongoing efforts to quantify uncertainties in the estimated thicknesses of Central Tennessee sedimentary rock formations.  The larger research goal is to understand the origin of thickness variations in carbonate strata deposited during Late Ordovician (~453 Ma) tectonic uplift of the Nashville Dome.

Additional Abstract Information