Using Historical Imagery to Monitor and Assess Threats over Time

Don Evans

USDA Forest Service Remote Sensing Applications Center

Remote sensing provides perhaps the best means to assess changes over time.  In particular, aerial photography provides an invaluable record of land use and land cover conditions—frequently dating back to the 1930’s!  Most forests have repeat photography on approximately a ten year cycle.  This rich photo record can indicate changing threat conditions thru time including threats such as: insect damage, fuels buildup, unmanaged off-highway vehicle use, and loss of open space. 

We’ve long recognized and valued the quality information content of photos; however, we’ve also long struggled with how to get our photos into our GIS.  Current technologies have converged within the Forest Service that allow us to get our photos into a GIS rather easily.  Within the GIS we can evaluate, analyze and document important changes.

This paper discusses historical photo data sources, software solutions and techniques for historical photo orthocorrection—along with examples of using historical imagery to document selected changing threat levels over time in several locations.

The methods described in this paper are available in all areas and provide the most consistent and objective method for detecting, assessing and monitoring changes through time.

Monitoring Methods Session - Tuesday Afternoon

corresponding author:

Don Evans
USDA Forest Service
Remote Sensing Applications Center
2222 West 2300 South
Salt Lake City, UT 84119
801-975-3757
dtevans@fs.fed.us