CTAP Sampling Design
- Spatially balanced, random sampling
- Sampling units are based on 36-square-mile townships; there are 1,765 of these townships within Illinois
- Each “habitat type” in a township is given random numbers and sites are sampled sequentially until a suitable site, based on protocol parameters, is found.
- Initial selection was prior to the 1997 field season.
- Site sampling is on a 5-year rotation.
Sampled to date
- Forests: 156
- Grasslands: 185
- Wetlands: 180