Whitehall Forest GPS Test Site

The Whitehall Forest GPS Test Site was developed in 2004 and is the largest publicly accessible, forested, tightly controlled, GPS test course in the United States. The positions of a set of nearby established survey monuments were determined using a survey-grade GPS receiver (Ashtech Locus GPS) according to protocols (static data, 4 hours of data collection, etc.) that would allow the positions to be considered and accepted by the National Spatial Reference System (NSRS). The positions of the monuments were processed using the U.S. Department of Commerce, National Oceanic and Atmospheric Administration's Online Positioning User Service (OPUS) (www.ngs.noaa.gov/OPUS). The positional precision of these monuments was less than 2 cm. The closed traverse network that represents the Whitehall Forest GPS Test Site corners was then established by registered surveyors using a Topcon GTS-211D instrument and the NSRS monuments as a base. The closure of the points within the Test Site (as represented by a closed traverse connecting the points) was estimated to be 1/92,137. Given this, we consider the GPS Test Site to be a highly accurate model around which GPS equipment could be tested in forested conditions.

Surveyed points have a brass survey cap that is flush with the ground, connected to a 2-foot piece of rebar, and surrounded by about 6 inches of cement (2 feet deep).

1. Ten points are in an older pine forest; trees are approximately 70 years old.

2. One point is in a young pine forest; trees are approximately 20 years old.

3. Twenty-six points are in an older hardwood forest; trees are approximately 70 years old.