Ground Sample Inventories

Forest Resources Commission (FRC) recommended a review of the provincial resource inventory process in its 1991 report The Future of our Forests. The result was the Vegetation Resources Inventory (VRI). VRI is a photo-based, two-phased vegetation inventory design consisting of:

  • Phase 1: Photo Interpretation – Photo interpretation involves estimating vegetation polygon characteristics from existing information, aerial photography or other sources. No sampling is done.
  • Phase 2: Ground Sampling – Ground Sampling uses mandatory Net Volume Adjustment Factor (NVAF) sampling to help calculate inventory adjustment factors.

Ground Sampling determines how much of a given characteristic is within the inventory area. Ground samples alone cannot provide the specific locations of the inventoried land cover characteristics.

Net Volume Adjustment Factor (NVAF) sampling helps account for errors in the estimates of net tree volume. NVAF is:

  • Calculated from the ratio of actual to estimates of sample tree volumes
  • Applied as a correction to VRI ground sample volumes.

This data, used in conjunction with the original ground sampling data, provides an unbiased estimate of the net volume in the project area.

Overall, ground measurements provide a level of certainty about means and totals for key attributes for the population.