Lines can be created around the outside edge of polygons on polygon or surface covers. This type of conversion is useful when you have a surface cover and you want to draw lines around similar areas. For example, with an aspect surface cover, you would want the areas facing in the four compass directions and the flat areas to have lines drawn around them. Many planning questions require the knowledge of the distance between two items. Corridors and buffers are the most common type of proximity analysis.
Corridors are constant or variable width areas around an element or feature.
Each pixel within the specified distance is given a user defined Z value while the pixels outside the corridor or buffer are given a different Z value. Other proximity programs create surface covers where each pixel contains a distance to the starting element or feature. This type of surface cover can be overlaid with polygon covers to determine the minimum, maximum or mean distance from the polygon to the starting location. Thiessen polygon use distance calculations to identify the area of influence around a series of starting points. As the polygons grow outward from their starting points, they eventually touch their neighboring polygons and stop spreading.