The Colorado Division of Wildlife uses National Aerial Photography Program (NAPP) aerial color infrared (CIR) photographs to map riparian vegetation. These photos are flown at a height of 20,000 feet and purchased from the USGS EROS Data Center as a 9" x 9" film positive at a nominal scale of 1:40,000. It is important to remember that riparian habitat is delineated both by the landform it lies within as well as the vegetation it supports. It is for this reason that riparian mapping be done in stereo (3-D) and not from a single photograph. Approximately ten (10) NAPP aerial photos per quad are needed for stereo overlay and complete quad coverage. Riparian vegetation is mapped on a 7.5' Quadrangle basis at a scale of 1:24,000.
The photos are arranged on a
Bausch & Lomb stereo
zoom transfer scope and registered to the corresponding topographic mylar base
map
for purposes of spatial accuracy.
Bausch & Lomb Zoom Transfer Scope
Although the maps are produced at a scale of 1:24,000 the delineation is performed at a scale of 1:12,000 by use of a 2x lens which greatly increases both the spatial and classification accuracy. Combining the use of a pre-defined Classification Scheme, and while viewing the imagery in stereo to better ascertain vegetative and geomorphological structure, the photo-interpreter delineates riparian vegetation as either a polygon or line feature using a '000' rapidograph. Separation of riparian vegetation classes are done first by color and structure, then texture, and finally by association with riparian topography. The minimum mapping unit (MMU) is 1/2 acre and groupings this size or larger are depicted as polygons. In many cases, polygons as small as 1/10 acre have been delineated by the photo-interpreter during the course of this project. Riparian vegetation less than 80 feet in width is recorded as a line feature. A line feature must be at least 500 feet in length to be recorded. If a line feature is less than 500 feet long it is then incorporated into another riparian type. Delineation of the line and polygon features is done on a separate piece of stable-based mylar overlayed on and registered to the topographic mylar map.
Once the initial delineation is complete, the photo-interpretor makes a second pass and assigns attributes to the features, again, using the riparian classification scheme. The classification scheme makes use of a dominant/subdominant methodology for describing riparian vegetation. Unless a polygon is at least 75% homogeneous it is broken out with the dominant category listed first followed by the subdominant category. The dominant/subdominant attributes are separated by a slash ( / ). For example, RS/RH equals "riparian shrub/riparian herbaceous" with shrub being the dominant category within the mapped polygon. Annotation labels are delineated on a separate sheet of stable-based mylar from that used to delineate the riparian lines and polygons. This facilitates the scanning, editing, and digital processing of the data.
Example of raw riparian data
After the riparian vegetation is delineated and annotated it is mechanically scanned at a minimum resolution of 300 dpi. This resolution achieves optimal results for digital editing and attributing. The digital file is edited and attributed using LTDOS, LTPLUS, ARCSCAN, or a similar line tracer program. The resulting digital files, along with the original delineation, are then provided to the Colorado Division of Wildlife for final digital processing into an ArcInfo Geographic Information System (GIS). Both line features and polygon features are imbedded in a single Quadrangle file which greatly facilitates data storage and data dissemination.
There are several important data fields that have been created in the ArcInfo attribute table when the data is digitally processed. Awareness of these attributes will greatly facilitate your use of the digital data and is described in greater detail in the MetaData. The original "raw data" is always entered either in the DATAF or DATAB attribute fields. The DATAB field was created to maintain the original attributes on those Quads mapped during the USFS/CDOW Cooperative Riparian Habitat Mapping Process (Table 2). This was to ensure data integrity as we instituted the revised classification scheme (Table 1) and "cross walked" the two classification schemes to produce seamless data. The DATAB attribute field contains those "raw data" attributes being used with the current classification scheme. The DOM attribute field contains the dominant vegetation type indicated in the raw data field and the SUBD attribute field contains the subdominant vegetation type contained in the raw data field. These two fields were created to facilitate data display, analysis, and plotting, and are the fields upon which the ArcView Legend Files depend.
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