Investigating the Oxbows and Testing Metal Detector Efficiency

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Figure 12. Aerial photograph of the entire battlefield taken in 1954. Old meander scars are clearly evident in the Reno Valley Fight area showing the river changed course in the past. Courtesy Little Bighorn Battlefield National Monument. 23
Thompson, Tweedy, Marshall Maps Compared to the 2005 Orthophotographic Map The Thompson/Tweedy/Marshall Maps are the famous USGS cartographic maps so many researchers rely upon as the earliest accurate depiction of the battlefield. Until the 1960s it was the only topographic map readily available to most researchers. The field data was collected in 1891 and the map first printed for the public in 1908, and it has been in print ever since (Donahue 2008b:257-263). As printed in 1908 the map has two parts, the upper section is a topographic map of the Custer battlefield south to Reno Creek done at a scale of 1 inch equals 2000 feet with contour interval of 25 feet. The boundaries of the Custer battlefield are noted, probably the fence line that set the battlefield apart from the surrounding range land, and within the boundary there are black dots representing the marble markers that were placed on the field earlier in 1891 by Capt. Owen Sweet. The second map below the topographic map is more detailed rendering of the Custer battlefield with only the marble markers noted and annotated. The scale of the marker map is 1 inch equals 440 feet. True north and magnetic north are indicated for the first time on any map. The 1891 topographic map matches the modern topographic map very well (Figure 13). The 1891 map has less detail and precision compared to the modern maps. This is expected given the map making theory and methods used at the time the 1891 map was made. All major topographic features match as do stream and drainage locations. There appear to be major changes in the river valley southwest of Last Stand Hill where the river has now shifted creating steep bluff areas that were once less steep grades. Likewise there are changes in the valley below Weir Point where the river has eroded and changed the bluff configuration to some extent, as well as the river channel itself. These changes are documented in Jason Pitsch and Keith Wert (2007) on the river and land changes in the area of the Reno Valley fight. The overall RMS error for the 1891 topographic component is 4.6 meter RMS error or 15 feet indicating a less than 1% correlation error between it and the modern imagery (Scott and Donahue 2010:11-12). The 1891 map depicts all three oxbows adjacent to Custer field, but their configuration is at odds with the earlier maps and the modern river meander locations (Figure 14). The northern oxbow is in the correct spatial location, but is larger and shown flowing further west than earlier maps and the modern channel. The Deep Ravine or middle oxbow is shown in the same location as early maps and the modern river channel, but it is depicted as a more open U-shape than the convoluted meander depicted on earlier maps and the current channel. The southern oxbow is also shown on the 1891 map, but it is a broad U-shaped meander located further south and east than the current oxbow. The modern aerial imagery does not show visible meander scars in the valley where the 1891 map shows the meander, so this location should be considered questionable until a professional geomorphologic study of the river can be undertaken. Preliminary Map Analysis Summary It is clear that many of the early maps made of the Custer battlefield proper and its environs have varying degrees of error inherent within and among them when compared to the highly precise modern aerial imagery and planimetrically correct USGS topographic maps. Excusably and perhaps the worst of these were the early Lt. Edward Maguire maps, which were hurriedly 24
Page 1 and 2: Investigating the Oxbows and Testin
Page 3 and 4: Acknowledgements The oxbow investig
Page 5 and 6: List of Figures 1. The oxbow areas
Page 7 and 8: Figure 2. A comparison between a 19
Page 9 and 10: landform evidence the origin of the
Page 11 and 12: successful in its own right yieldin
Page 13 and 14: Metal detecting operations were des
Page 15 and 16: Figure 4. Eroding neck of southern
Page 17 and 18: machine. Both targets were found on
Page 19 and 20: Preliminary Assessment of Historic
Page 21 and 22: Figure 7. Lt. Edward Maguire 1876 m
Page 23 and 24: Figure 8. The 1881 Maguire map (Map
Page 25 and 26: Figure 9. The P. H. Norris map over
Page 27: Figure 11. The 1901 Sampson map ove
Page 31 and 32: Figure 14. The 1891 river course in
Page 33 and 34: Figure 15. Location of metal detect
Page 35 and 36: Figure 17. Metal detector targets m
Page 37 and 38: area for an average of 81.5% find r
Page 39 and 40: References cited: Alt, D. and D. W.
Page 41: Scott, Douglas D. and Michael Donah

Investigating the Oxbows and Testing Metal Detector Efficiency

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