1. GIS and Landscape Archaeology along the Anacostia River
Geoarchaeological Study of Joint Base Anacostia-Bolling

2. Outline
Background
Approach
Analysis
Field Refinement

3. Background
Joint Base Anacostia-Bolling (JBAB) wanted to evaluate the potential for buried archaeological landscapes throughout JBAB as current survey coverage is incomplete.
Many areas have been covered at varying depths. In order to correctly survey these areas to determine if cultural resources exist, a model for new fill depths was needed.

4. Background
Large areas of JBAB can be excluded because they consist entirely of made land: these include virtually all of the Anacostia Annex property as well as a band along the Potomac River shoreline however this area was not well defined.

5. Approach
Marstel-Day created a 3-D terrain model of the Anacostia River shoreline based on maps from 1888 and performed 3D geospatial analyses to determine fill depths of current Anacostia Shoreline.
Once completed, Louis-Berger and Geo-Sci Consultants modified the vertical adjustment based on field measurements

6. Analysis: Georeference and Digitize
Maps from 1888 were Georeferenced and contours were digitized.
Team used ArcScan to quickly generate a preliminary contour layer.
Contours were further refined by hand.

7. Analysis: Datum Shift
After the contours were digitized the team applied a datum shift to the 1888 elevation values to account for changes in how elevation values were calculated between 1888 and current elevation data.
Datum shift was to account for changes in how elevation values were recorded in 1888 and today.
Value was provided by Louis-Berger based on work completed previously in the region.

8. Geospatial Analysis
Modified Elevation values in 1888 were subtracted from current values determine the minimum dig depths for future cultural surveys completed at JBAB

9. Model Refinement
Maps were originally georeferenced using features believed to be consistent between 1888 and today
Railroad
Streets
This proved to be inaccurate as:
Manmade features may have been moved since 1888
The cartographic production accuracy in 1888 may have been poor
This initial georeferencing produced an erroneous product

10. Model Refinement
When analysis to determine the change in elevation was conducted, values stated areas with no significant change (areas of dense vegetation and High slope) had value changes of more than 50 feet.

11. 3D Visualization
When visualized in 3D the error in georeferencing is obvious
Current Elevation
Current Elevation and Historical Elevation Overlaid
Historical Elevation

12. Model Refinement
The team found that many terrain features were generally the same in both the model from 1888 and the current terrain model
These features were used to refine the georeferencing model
The new model was deemed sufficient to determine the soil fill depths
1888 Elevation Model
Current Elevation Model

13. Final Analysis output
The new raster difference map depicted less severe changes in elevation.

14. Onsite Model Refinement
LB and Geo-Sci Consultants excavated 23 soil cores and 6 trenches to test the modelling
Of 29 sample locales, 15 found evidence of historic landscape. Rest were disturbed from modern construction
Unexpected benefit: identified two new sites

15. Onsite Model Refinement
Examined variance between calculated and observed depths
Found patterned, normal distribution of error
Calculated the mean error and then revised the GIS analysis
Standard deviation for the refined model is calculated at 1.2 feet

16. Diego Negron, GISP Paula Bienenfeld, Ph. D. Gregory Katz, RPA
Questions?
Diego Negron, GISP
Paula Bienenfeld, Ph. D.
Gregory Katz, RPA