High Resolution 3D Images of Natural Terrains and Landslides

As a rule of thumb, landslides tend to occur repeatedly at the same or nearby locations over a long period of time because they are related to the physical characteristics of an area. The soil of a landslide area is usually weak to begin with and prone to weathering from several different forces such as wind and water. As a result, there will usually be substantial erosion occurring between major landslide episodes and the rate of erosion is very important in evaluating the stability of the slope and the tendency to the next landslide. Normally the soils consisted of the slopes that collapsed repeatedly are called colluviums. Colluviums are soils with low shear strengths in terms of their cohesions and frictional angles. Colluviums are also believed to be the soils comprising the landslide site under long-term study by the authors near the Houshanyue hiking trail of Taipei City, Taiwan. Because landslides all look alike to untrained eyes, it is easy to lose orientation and bearing when a person looks at individual photos taken at the site. To better orient viewing to the details of the photos, this study developed a method to take very high resolution images (usually in the gigapixel range) of the landslide sites using the GigaPan device. The images were then further processed to become high resolution 3D anaglyph images. A pair of low-cost red and cyan glasses (red over the left eye) is all that is needed to view the 3D images. The authors illustrated the benefits of 3D images in visualizing scenic objects by taking a collection of photos at the Houshanyue site. The results showed an improvement of depth perception and a better determination of directions. For example, the depths of gullies were visually more easily comprehended and the trees could be seen to lean forward in addition to leaning to the right.