2005
San Pablo Bay Wetlands, Sonoma County, CA LiDAR Mapping
In 2005, HJW was contracted by Wetlands and Water Resources to
produce 1’ contours and orthophotography of the San Pablo
Bay wetlands. The contour mapping was accomplished by using a
combination of LiDAR data and traditional photogrammetric analysis.
Utilizing softcopy photogrammetric compilation, the LiDAR “bare
earth” points were superimposed on the stereo models and
manually edited. The compilation technician interpolated breaklines
through the LiDAR data set by snapping to individual points. In
this scenario, the horizontal placement of the breaklines is controlled
by the experienced compiler, but the vertical accuracy of the
vertices along the breakline is controlled by the LiDAR data.
A digital terrain model consisting of the manually collected breaklines
and LiDAR mass points was used to generate the 1’ contours.
By using this method, the final contour map has the pleasing graphic
quality of traditionally compiled photogrammetric mapping, which
proves to be easier to interpret than automatically generated
contours from LiDAR alone. Because the LiDAR data was used as
the source of vertical accuracy, the photography used for the
manual interpretation did not have to be at a scale required for
1’ contour mapping, thereby providing a savings in photogrammetric
costs to the client. |
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