Geoscience Reference
In-Depth Information
Fig. 10.3 Land cover classification of Lake Erie tributaries study area after reclassification of
select areas
10.4.2 Spatial Analysis
ArcGIS 8.3 provides a built-in platform for spatial analysis. However, none of the
available tools in ArcGIS were able to directly solve the problem of calculating the
proportions of each land cover type within both 100 m and 500 m buffers around
each IBI sample point. Alternatively, a hybrid-type method utilized multiple soft-
ware packages to complete this task. To determine the land use within a distance
of each sample point buffers of 100 m and 500 m were created around each IBI
and QHEI point feature, producing a new polygon for each buffer. To avoid area
measurement problems due to multi-part geometry among spatially disconnected
like-attribute features, the “explode multipart feature” function was applied to
create discrete features. After this critical step was complete the land cover data
layer was clipped to the 100 m and 500 m buffers, which produced two shapefiles of
(1) all land cover within 100 m of each sample point and (2) all land cover within
500 m of each sample point. The area of each polygon was calculated and appended
to the attribute table of each of the clipped land cover layers using Visual Basic for
Applications (VBA) statements in ArcGIS.
Spatial queries were run to join the IBI and QHEI point data to the land cover
data. This process assigned the appropriate sample point ID to each land cover
