Visual Impact Assessment Guidebook
Table of Contents
Sight line plotting instructions and presentation criteria
- Using the best topographic map scale available, plot sight lines to determine the areas
visible from each viewpoint. Sight-line plots determine the extent of visible
alteration(s) from viewpoints; the sight-line map (topographic map) shows the direction of
lines of sight from the same viewpoints.
- Based on the sight-line plots, indicate on the topographic map the portion(s) of the
proposal(s) that would be visible.
- Plot sight lines (also called "topographic sections or profiles") using the
best scale available (preferably at 1:10 000 or larger) from each important viewpoint.
- Label each sight-line plot with the viewpoint number, opening number, sight line number,
and scale of the topographic map used for the plotting.
- Provide an elevation bar on the upslope end of the profile and a distance scale on the
horizontal bar (see the following example).
- Identify the start and end of the opening with a tree representative of stand height
class (see Figure A7.1).
- Indicate road locations within the block.
- Shade in the visible area and transfer these data onto the topographic map.
- Minimize vertical exaggeration; the recommended vertical exaggeration is 1:11:1.5.
Figure A7.1 Plotting a sight line.
Making topographic sections from a contour map. (a) Draw line of section on map from
viewpoint across the relevant part of the terrain. Project lines at right angles from
where the line of section cuts the contour to the corresponding heights on the sectional
drawing above. (b) Connect the points on the section and draw line(s) of sight from the
viewpoint. (c) Illustrate tree heights at appropriate age intervals as required.