Preview: Computer assistance for visual management of forested landscapes

Abstract

Myklestad, E. and Wagar, J.A., 1977. PREVIEW: computer assistance for visual management of forested landscapes. Landscape Plann., 4: 313–331. The PREVIEW computer program facilitates visual management of forested landscapes by generating perspective drawings that show proposed timber harvesting and regrowth throughout a rotation. Drawings show how changes would appear from selected viewing points and show landscapes as either a grid of distorted squares or by symbols representing trees, clearings, water, rock, etc. PREVIEW can also show roads and other linear features. PREVIEW requires digitized data for uniformly spaced points in a grid of up to 100 columns and 80 rows. For distorted square drawings, only elevations are needed. For drawings with symbols, data must also include vegetation or surface type codes and, when appropriate, tree heights. At a spacing of 100 feet (30.48 m) between adjacent points, the maximum (100 × 80) grid covers approximately 2.9 square miles (750 ha). In addition to the cost of preparing data, computer and plotter costs are incurred. These depend on the computer and plotter used, the size of the grid, the number of points visible from the viewing point, and the density of symbols used. Computer (CDC 6400) and plotter (Calcomp 936) costs were approximately $16 for a drawing that plotted vegetation and ground cover symbols for approximately 2,800 visible points from a data grid of 7,200 points embracing 1,653 acres (6.69 km 2). PREVIEW is controlled by a series of instruction cards that specify data entries, viewing point(s), angle(s) of view, drawing center point(s), scale of drawing(s), rates of tree growth, normal and shelterwood tree densities, representation as distorted-square or vegetation and surface-type symbols, and year(s) after beginning of rotation.