1. Confidentiality of plot coordinates - Alternatives?
Sue Willits
Forest Inventory and Analysis Program
August 1, 2002
National FIA Users Group Meeting

2. We still need to discuss the “HOWS” of masking data and
What it means to you the Users……….
Forest Inventory and Analysis

3. Alternatives for Masking Ownership
Step 1: Review every county for each ownership category to determine if there are a minimum of 3 owners in each category (industry vs. other).
If not, then we combine counties or collapse owner categories

4. Alternatives for Masking Ownership
Step 2:
Option 1: Fuzz coordinates so that 3 or more owners are in the general area. (could be moved to county center).
Pro: Individual plot attributes are maintained
Con: Spatial detail will be variable
Must be automated
Could create inconsistency between counties if
large fuzz was used instead of county center.

5. Alternatives for Masking Ownership
Step 2:
Option 2: Create strata within a county by Forest Type and Stand size. Provide average data for all plots within the strata. Provide fuzzed coordinates with the averaged data.
Pro: Creates a simple spatially explicit database
Consistent for county level reporting
Con: Pre-defined Strata of interest
No individual plot data
May mask spatial data for non-tree variables
Assumes uniform plot weights for area expansion
Plots are not necessarily contiguous

6. Alternatives for Masking Ownership
Step 2:
Option 3: Swap 25% of the plots with similar plots (forest type and stand size) across all owners within the county. Try to find plots in close proximity.
Pro: Would not require checking for rule of 3
Automation could happen fairly quickly
Would provide consistency
Con: Data may be too similar to truly provide masking