THE USE OF DIGITAL ORTHOPHOTO QUADRANGLES IN VEGETATION
MAPPING

Janis Ruhser
U.S. Geological Survey, Biological Resources Division, Environmental
Management Technical Center, Onalaska, WI  54650

Orthophoto quadrangles from the USGS are produced from National Aerial
Photography Program imagery.  This quarter-quadrangle centered photography
(3.75 minutes of latitude by 3.75 minutes of longitude in geographic extent) is at
approximately 1:40,000 scale, producing 1-meter resolution orthophotos. 
National High Altitude Photography (1:80,000 scale) is used to produce 2-meter
digital orthophoto quadrangles (7.5 minutes of latitude by 7.5 minutes of
longitude in geographic extent).  Relief displacement is removed from the aerial
photography, resulting in an orthophoto which allows for true area and distance
measurement.  The image characteristics of the photograph are retained,
however, allowing features that may not appear on regular maps to be displayed. 
These image characteristics in a geometric map form make orthophoto quads
ideal for use in vegetation mapping.  Used as basemaps for the National Park
Mapping project, the digital orthophoto quarter-quads (DOQQ's) present much
more vegetation information than a standard USGS topographical quad.  Also,
the larger scale (1:12,000) is helpful in increasing accuracy.  The DOQQ files are
imported to a geographic information system (GIS), running ARC/INFO
software on a UNIX operating system.  Once converted to a format that
ARC/INFO can use, the images can be overlaid with a quad boundary, and scale
bars, north arrows, titles and other map elements added to create the quad map
output.  This output is then used as the basemap in the automation of
photointerpreted vegetation data.  

Keywords:  orthophoto, vegetation mapping, DOQQ, aerial photography, image

Janis Ruhser
Environmental Management Technical Center
575 Lester Avenue
Onalaska, WI  54650
(608)783-7550 ext. 33
janis_ruhser@nbs.gov
Poster presentation, no platform presentation