OK, this weeks second raster bulletin, copied straight from what the
developer sent out to us all at Safe.
Mark
------------------------------------------------------------
Safe Software raster development has added new raster processing to
our flagship FME product. The VectorOnRasterOverlay Factory and its
corresponding PointOnRasterOverlayer transformer are now available in
the FME UT and in Workbench. A new documentation chapter has been
added to assist our users in understanding this new processing.
The intent of this factory is to group all vector and raster
combination operations that produce multiple vector features as
output. Currently we have implemented the combination of point and
raster input to retrieve the raster values as attributes on the output
points. This is only a subset of what is possible with the factory as
the future will likely see us adding more vector on raster operations
that are not specific to points and may alter the input vector
features in ways other that the attributes such as measures.
The process of determining which cell values in the raster are most
appropriate to attribute to each input point is called interpolation.
Several different interpolation techniques are available to try to
determine an accurate value though the techniques tend to vary in
performance and accuracy. The initial implementation of the
PointOnRasterOverlayer offers the three most common types of
interpolation: NearestNeighbor, Bilinear and Bicubic. These the common
interpolation types are also previously employed by the both the
RasterResampler and Reprojector.
Nearest Neighbor: Fast and less accurate. Provide the closest single
cell value.
Bilinear: Moderate speed and accuracy. Weights the closest 4 cells to
determine the resultant value.
Bicubic: Slow and more accurate. Weights the closest 16 cells to
determine the resultant value.
Several customers have requested various vector on raster overlay
operations to leverage the combination of data stored in rasters, for
example Digital Elevation Models (DEMs), with existing vector location
data. A simple example of this might be to combine points indicating
the location of cell towers with DEMs indicating the height of the
terrain in the area so that the height at each tower location can be
attributed to each tower location, thus adding to the total height of
the tower.
The VectorOnRasterOverlay is now available in FME 2007 betas as of
build 4259+.
For insights into what's up at Safe Software and what's on the development
horizon, visit Safe's blog at spatial-etl.blogspot.com.
Safe Software has also made slides available that outline enhancements planned
for FME 2007. The slides are from the "Road Ahead" presentation given on Day 2
of the FME Worldwide Users Conference. To view these slides, visit
www.safe.com/2006uc.
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