Yosemite National Park fire history polygons, 1930 - 2011

Yosemite National Park

Fire history extents for all fires that burned at least partly within Yosemite from 1930 through 2011. Dataset includes fire casue, year of fire, start and end dates, and other information. Fire history taken from historic records kept at Yosemite National Park. Fires in more recent years were recorded from fire perimeters drawn on paper maps and/or recorded by GPS Unit. Original data was interpreted from historical fire records held at Yosemite National Park in the late 1980s. Polygons depicting burned areas were drawn on 1:62,500 USGS maps (15" series) based on written descriptions in the fire records. Fires less than 10 acres in size were depicted as points. Mylar film was placed over paper maps and registered with tic marks at map corners. Fires were traced on Mylar and sent to a contractor for digitizing into SAGIS vector format. Fires depicted as points were given the area noted in the fire records by buffering the points. SAGIS data was converted to GRASS format when Yosemite migrated to GRASS. GRASS data was converted to Arc/Info coverage format when Yosemite migrated to Arc/Info in 1995. Some vector data was lost in conversion from GRASS. In those instances, polygons were vectorized from raster versions that remained in GRASS. Each year from 1995 - 2000, fires were input into Arc/Info by digitizing 1:24,000 USGS paper maps (7.5" series) or from Trimble GPS readings. Starting 2001, all larger fire perimeters were acquired through ground GPS or helicopter GPS reconnaissance. Small fire point locations were acquired through ground GPS or helicopter GPS and buffered to approximate fire size.

Yosemite National Park fire history polygons, 1930 - 2011

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