Vegetation Classification and Mapping Project Report - USGS

Base Map Class Development
names being adjusted based on the input
of park staff during that meeting.
3.1.5. Base Map Automation
The Geographic Information Systems
Spatial Analysis Laboratory (GISSAL) in
the Department of Geography at Kansas
State University provided the technical
expertise to automate the polygons
and associated map class and modifier
assignments, creating a spatial vegetation
map database.
3.1.5.1 Aerial Photograph Mosaic
SCPN provided GISSAL with one
complete set of the 1:6,000 true color
aerial photographs. Each of the 9 in x 9 in
contact prints was scanned at a resolution
of 500 dpi and full color depth, then
saved in TIF image format, resulting in
an uncompressed file size of 74.5 MB
per photo. Digital versions of the aerial
photographs were cropped in Adobe
Photoshop 6.0 (Adobe Systems Inc., San
Jose, CA) to remove the black borders
present on the original hardcopy photos.
Orthorectification was performed with
ER Mapper 7.0 (Leica Geosystems, San
Diego, CA) using National Elevation
Dataset (NED) digital elevation models
(DEMs) as the height reference. Northing
and easting for ground control points
(GCPs) were determined from an existing
low-resolution digital orthophotograph.
Between four and six GCPs common
to each scanned aerial photograph and
corresponding digital orthophotograph
were defined within ER Mapper until a
root mean square error (RMS ) of ≤ 1
error
pixel (equivalent to an error of less than
0.3048 meters or 12 inches) was achieved.
When necessary, additional GCPs were
identified to meet this threshold. The
output projection and datum for the final
product were UTM Zone 12N and NAD
83.
Individual orthorectified photographs
were compressed at a ratio of 1:35
and saved in ECW format. Each of the
individual orthorectified digital photos
was combined in a mosaic operation
and color-balanced in ER Mapper to
produce the final seamless 1:6,000 scale
digital photomosaic, at 0.3048 meter or 12
inch pixel resolution, for the park and its
environs.
3.1.5.2 Vegetation Map Database
Development
The photointerpretation team provided
more than 1000 transparent polyester
sheet overlays with map polygon
delineation to GISSAL. Each overlay
included boundary information for
delineated map polygons, along with codes
representing the numeric reference for the
base map class, including any applicable
modifiers. Overlays were scanned and
converted into black and white digital
raster files (TIF format) for processing and
archiving.
Digital versions of the scanned overlays
were orthorectified in ER Mapper 7.0
using 1/3 arc second (10 meter) digital
elevation models (DEMs) from the
National Elevation Dataset (NED) as
the height reference, and the previously
created digital orthophotomosaic as the
base map. As was performed previously
with orthorectification, 4-6 GCPs common
between the scanned overlays and the
high-resolution orthophotomosaic
were defined within ER Mapper until
a horizontal root mean square error
(RMS ) of ≤ 1pixel (equivalent to 0.3048
error
meters or 12 inches) was achieved. If
necessary, additional GCPs were identified
to meet this threshold.
After orthorectification was completed,
each overlay was subjected to a rasterto-vector
conversion using the ArcScan
extension available with the ArcGIS
9.2 (ESRI, Redlands, CA) software.
Vector line features generated from the
scanned vegetation boundaries were
“edge-matched” with boundary lines
generated from adjacent overlays and then
converted into polygon features. Map
unit attribute information, read directly
from photointerpreter markings on the
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