Description
Model Based Approach
Model-based errors for aggregate AGB estimates were computed following the approach described in the CEOS Aboveground Woody Biomass Product Validation Good Practices Protocol (Section 4.2.2).
To produce pixel-level residuals, “observed” values were sampled from the 95% conformal interval at each pixel, and differenced with the pixel prediction. 100 iterations of this process were executed to produce a pixel residual as the average residual across the 100 iterations, as well as a pixel residual variance.
An “MSE” value for each aggregation unit was computed as the sum of the following components:
- covariance of predictions
- average pixel residual variance
- covariance of pixel residuals
Data
The Warren, Washington, Essex LiDAR region was leveraged for this analysis. Note that this area is relatively homogenous with respect to landcover, so we might expect these error estimates to be optimistic relative to other regions.
The LINMOD ensemble predictions were used in this analysis, but were masked to only include LCMAP tree cover and wetland classes. Pixels falling in any other class were set to NA and excluded from the analysis.
2019 tax parcels were used as aggregation units. These aggregation units make sense from an application standpoint, though perhaps more arbitrary units of aggregation would be more suitable.
Results
Summary of Error Components
Average Contributions:
- Prediction Covariance: 3.99%
- Average Residual Variance: 95.61%
- Residual Covariance: 0.4%
Distribution of % Error (capped at 200%)
Parcel Errors By Parcel Size
RMSE By Parcel Size
% Error (capped at 200%) By Parcel Size
Summarized Parcel Errors for Size Groupings
Groups are exclusive, where each point along the x-axis represents the center of a 10 acre summary group. So where the x-axis says ‘55’ we are summarizing all parcels larger than 50 acres in size and smaller than or equal to 60 acres in size.
Parcel Maps
Percent errors capped at 200% for figure clarity
