VASIP 2: Software Update for Visualizing Propagation of Measurement and Process Errors in VASI Based Site Models
Keywords:
Variable-age site index, VASI, Base-age invariance, BAI, Self-referencing models, Polymorphic height growth, Measurement error, Process error, Error propagation, Parameter sensitivityAbstract
This note follows Cieszewski and Wawrykowicz (2025) on VASIP 1.0 and presents VASIP 2, version 2.0.20, for variable-age site index (VASI) curves. The height model is unchanged, and the program retains sixteen historical Alberta and Saskatchewan parameter sets. New functions include: (1) animated graphs with live reference movement; (2) nested conditional bounds at one, two, and three standard errors (SEs); and (3) paired graphs of absolute and relative deviations and bound-sum bias, which measures bound asymmetry about the central curve. Site-index and height-crossing-age readouts update live with the reference point. Adjustable graphs, file imports and exports, named projects, and reporting tools further extend the workflow. Measurement-height variation and global-coefficient variation can be viewed separately or jointly at the selected sensitivity settings. In the program, Process is represented by global-coefficient variation, which changes growth efficiency (the relative height-growth rate). This propagates the coefficient uncertainty represented by the reported SEs, including any effects of lack of fit reflected in them, without simulating stochastic residual disturbances. The program includes a complete user guide; we trace its parameter sources to the 1991 Alberta note and the 1993–1995 Saskatchewan records. The bounds are deterministic sensitivity envelopes informed by marginal coefficient SEs, with no verified probability coverage.
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