Calculating Visual Connectivity

1
Calculating Visual Connectivity an animated
series of slides demonstrating 2D and 3D visual
connectivity from increasing viewer height (0 to
20,000)
Prepared by Joseph K. Berry Keck Scholar in
Geosciences, University of Denver Principal,
Berry Associates // Spatial Information Systems
(BASIS) Fort Collins jberry_at_innovativegis.com We
bsite www.innovativegis.com/basis
2
Mount St. Helens Topography (project area)
3
Calculating Visual Connectivity (Approach)
Viewer Location
(300c, 114r) Point of Interest
Point of Interest
Minimum Visible Elevation 11,380 Feet
Seen
Not Seen
.
Viewer Location (33c, 454r)

Viewshed at 0 feet rise
4
Calculating Visual Connectivity (Approach)
Similar triangles can be used to determine the
minimum POI height needed to be visibly connected
Tangent Rise / Run (6312 ft 3219
ft) / (SQRT(134 33)2 (454 325) 2
98.4251 ft) 3093 ft / (163.835 98.4251
ft) 3893 ft / 16125 ft 0.1918 Height
(Tangent Run) Viewer Height
(0.1918 (SQRT(300 33)2 (454 114) 2
98.4251 ft)) 3219 ft (0.1918 432.307
98.4251 ft) 3219 11,380 Feet
Viewer Location
(300c, 114r) Point of Interest
Point of Interest
Minimum Visible Elevation 11,380 Feet
Seen
Not Seen
.
Viewer Location (33c, 454r)

Viewshed at 0 feet rise
5
Visual Connectivity (500 above the terrain)
Point of Interest

Seen
.
Viewer Location

Viewshed at 500 feet rise
6
Visual Connectivity (1000 above the terrain)
Point of Interest

Second Ridge
Seen
Second Ridge Elevation (187c, 258r) 7,799 Feet
.
Viewer Location

Viewshed at 1000 feet rise
7
Visual Connectivity (2000 above the terrain)
Point of Interest

Seen
.
Viewer Location

Viewshed at 2000 feet rise
8
Visual Connectivity (3000 above the terrain)
Point of Interest

Seen
Second Ridge 7,799 Feet
.
Viewer Location

Viewshed at 3000 feet rise
9
Visual Connectivity (4000 above the terrain)
Point of Interest

Seen
Second Ridge 7,799 Feet
.
Viewer Location

Viewshed at 4000 feet rise
10
Visual Connectivity (5000 above the terrain)
Point of Interest

Seen
Second Ridge 7,799 Feet
.
Viewer Location

Viewshed at 5000 feet rise
11
Visual Connectivity (6000 above the terrain)
Point of Interest

Seen
Second Ridge 7,799 Feet
.
Viewer Location

Viewshed at 6000 feet rise
12
Visual Connectivity (7000 above the terrain)
Point of Interest

Seen
Second Ridge 7,799 Feet
.
Viewer Location

Viewshed at 7000 feet rise
13
Visual Connectivity (8000 above the terrain)
Point of Interest

Seen
.
Second Ridge 7,799 Feet
Viewer Location

Viewshed at 8000 feet rise
14
Visual Connectivity (9000 above the terrain)
Point of Interest

.
Seen
Second Ridge 7,799 Feet
Viewer Location

Viewshed at 9000 feet rise
15
Visual Connectivity (10000 above the terrain)
Point of Interest

.
Seen
Second Ridge 7,799 Feet
Viewer Location

Viewshed at 10000 feet rise
16
Visual Connectivity (11000 above the terrain)
Tangent 0, therefore POI surface location is
seen
Point of Interest

Second Ridge 7,799 Feet
Surface Seen
Viewer Location

Viewshed at 11000 feet rise
17
Representing Geographic Space (2D and 3D)
18
Visual Connectivity (12000 above the terrain)
Viewer Location
Viewshed at 12000 feet rise
19
Visual Connectivity (13000 above the terrain)
Viewer Location
Viewshed at 13000 feet rise
20
Visual Connectivity (14000 above the terrain)
21
Visual Connectivity (15000 above the terrain)
Viewer Location
Viewshed at 15000 feet rise
22
Visual Connectivity (16000 above the terrain)
Viewer Location
Viewshed at 16000 feet rise
23
Visual Connectivity (17000 above the terrain)
Viewer Location
Viewshed at 17000 feet rise
24
Visual Connectivity (18000 above the terrain)
Viewer Location
Viewshed at 18000 feet rise
25
Visual Connectivity (19000 above the terrain)
Viewer Location
Viewshed at 19000 feet rise
26
Visual Connectivity (20000 above the terrain)
Viewer Location
Viewshed at 20000 feet rise