USGS Home
Contact USGS
Search USGS

Buffering (Map and Imaging Processing System, Micro-Images Inc., Lincoln, NE) converted line and point data to polygon data. Line data were converted by creating an encompassing polygon whose sides were parallel lines equidistant from the line and its end points. Point data were converted by creating a circular polygon with the point as the center. Average measurements used to buffer linear and point data were calculated from aerial photographs (D. Hertel, U. S. Fish and Wildl. Serv., unpubl. data). These provided an 8.2 m width for shelter belts; 14.6 m diameter for rockpiles and brush or grass areas not enclosed by a polygon; 14.6 m width for linear wetland basins; and 15.3 m diameter for point wetland basins. The buffered width for fence rows and vegetated strips between fields was 3.1 m. Linear road features that were buffered included road surfaces and right-of-ways (ROW). Measurements used to buffer road surfaces and ROWs were determined after consulting appropriate road authoritities (D. Hertel, U. S. Fish and Wildl. Serv., pers. commun.). For gravel roads, the road surface averaged 6.2 m and each ROW averaged 10.1 m for a total width of 26.4 m. The average values for paved roads were 7.6 m for road surfaces and 19.1 m for each ROW. Railroad beds averaged 6.1 m in width with ROWs that were 19.8 m wide.