Geoscience Reference
In-Depth Information
p
j
a
j
/
TIA
=
100
(8.1)
where,
TIA
total impervious area (ha)
p
j
sub-pixel percentage imperviousness for class
j
(%)
a
j
total surface area covered by imperviousness class
j
(ha)
j
imperviousness class (1,
...
,101)
This TIA calculation will be used throughout this chapter to present some spa-
tial and temporal change trends in imperviousness, based on an existing sub-pixel
impervious layer that can be used for developing environmental resource policy and
management options.
8.2.1 The Effects of Resampling Method on Values and
Distribution of Subpixel Imperviousness Classes
The 2001, 30 m imperviousness dataset is published and freely available for down-
loading as a raster dataset from a geospatial information provisioning system, the
Seamless Data Distribution System (U.S. Geological Survey
2008
). The impervi-
ousness dataset inherited the coordinate system - USGS Albers Equal Area (ALB),
of standard use in other USGS products such as the Landsat imagery used to gener-
ate it. Kentucky Single Zone in the State Plane Coordinate System (FIPS 1600) is the
Commonwealth's official coordinate system (Kentucky Administrative Regulations
2009
). For publication to the Kentucky Geography Network and subsequent spatial
analysis procedures, data layers needed to be converted to, and clipped to the state
boundary (Kentucky Division of Geographic Information
2009b
) so that the imper-
vious dataset could be more easily integrated with existing and planned geospatial
data. Wall-to-wall impervious cover and land cover change datasets are available for
Kentucky, except that post-processing of the data in order to be in a single recog-
nized and compatible coordinate system could introduce distortions to the statistical
estimates from the original dataset.
In order to make the USGS data more easily available to environmental man-
agers in the state, a decision had to be made in terms of the resampling method
to be used during reprojection from USGS's Albers Equal Area to Kentucky
Single Zone. Subpixel imperviousness values range from 0 to 100% and it presents
duality in that it can either be considered numerical (discrete or continual) or cat-
egorical, the effects of processing on spatial distribution of imperviousness were
examined by using the nearest neighbor (NN) and the bilinear interpolation (BI)
methods existent as utilities in ArcGIS/ArcInfo
R
9.3.1 (ESRI 2009; Lillesand et al.
2007
).
The Kentucky urban/rural interface can be characterized by an abundance of
mixed use subwatersheds with a range of imperviousness. Therefore, ten 14-digit
