Visual Impact Assessment Guidebook

Table of Contents

Appendix 8

Calculating percent alteration in perspective view

Proposed Alteration: Visual Simulation

Step 1. Using the visual simulation output produced, define and outline the visual unit or landform. Exclude those portions of the landform screened by vegetation and non-green areas, such as mountain tops, rock, snow, and ice.

Step 2. Measure the visible unit or landform (e.g., middle ground landscape unit = 37.5 cm2).

Step 3. Measure visible ground area of existing alteration that has not yet achieved visually effective green-up (e.g., current alteration = 1.8 cm2).

Step 4. Measure visible ground area of proposed alteration (e.g., = 4.7 cm2).

Step 5. Add existing non-VEG alteration and proposed alteration figures together to get total area altered.

Divide this figure into visual landscape unit figure to get percentage of unit altered (e.g., [(1.8 + 4.7) 37.5] 100 = 17.3%.)

Note: Repeat the above calculation for each of the viewpoints selected for design and simulation. Enter the percent alteration figure derived from each viewpoint on the visual impact assessment summary form (Appendix 2).


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