Examples

Following are two brief examples of using historical photography to detect and document changing conditions over time.

Fig. 1- Loss of Open Space

Aerial photography from 1969, 1977, 1988, and 1993 of a small portion of the Black Hills National Forest boundary were orthocorrected using the orthocorrection tools in ArcMap Image Analysis. Roads and buildings were digitized from each cycle of photography (within the chosen subset, there are no roads or buildings visible in 1969). Features digitized from each cycle of photography were symbolized with different colors. The results (Figure 1) clearly depict significant man-made changes that fragment the open space around the national forest boundary.

Unmanaged Recreation

Fig. 2- Unmanaged Recreation

Leica Photogrammetry Suite (LPS) was used to orthocorrect photography from 1967, 1976, 1988, and 1995 over a small portion of the Fishlake National Forest. In addition, we added orthocorrected NAIP imagery from 2004. The 1967 photography did not have a camera report, so we created one using methods described in Creating Pseudo-Camera Reports. Once all of the photography was orthocorrected, we added the existing travel management plan roads layer. Then we digitized new OHV trails as they became apparent on each cycle of photography (Figure 2).

This methodology was simple, easily verifiable, and produces a map of actual OHV trails. In addition, it was a simple matter to construct graphs of the rate of change from the digitized trail’s attribute tables (Figure 3).

Fig. 3- Unmanaged Recreation