Using Historical Photography to Monitor and Assess Threats over Time
Analysis of aerial photography is perhaps the best way to assess changes in landcover conditions. In the United States, most national forests have repeat photography on approximately a 10-year cycle. Analysis of this rich photo record can reveal changes in insect damage, fuels buildup, unmanaged off-highway vehicle use, loss of open space, and other landcover conditions. Current technologies now allow Forest Service employees to input photos into a geographic information system (GIS) accurately and easily, and important changes can be documented, analyzed, and evaluated within the GIS. This analysis discusses selected photo characteristics, available software solutions, and techniques for orthocorrection of historical photos. It also discusses two cases in which historical imagery was used to document selected changing threat levels over time.
- Introduction : Remote sensing—aerial photography in particular—provides perhaps the best means to assess landcover changes over time.
- Why Photography? : Aerial photography, like all remote sensing technologies, has advantages and disadvantages compared with other remote sensing tools.
- Why Not Photography? : Photography has its weaknesses, too.
- Tools for Getting Historical Photos in GIS : There is a fortunate convergence of technologies that makes it easier than ever to get historical photography into our GIS.
- Analysis Options : Once the multiple dates of photography have been orthocorrected, there are few limits to analysis options.
- Examples : Following are two brief examples of using historical photography to detect and document changing conditions over time.
- Resources : This section discusses where to find old photos and lists additional resources.
Encyclopedia ID: p3334
