RasterTiler
From fmepedia
RasterTiler is a Workbench Transformer.
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Description
Splits each input raster into a series of tiles by specifying either a tile size (Number of Columns and Number of Rows) or a number of tiles (Number of Horizontal Tiles and Number of Vertical Tiles).
Example
The attachment 'RasterTilerExample.zip|attached workspace' not found shows an example use of the RasterTiler transformer.
To tile data for Virtual Earth you should use the VirtualEarthTiler.
NB: This is actually a good illustration of working with raster data in general, and GeoTIFF data in particular, because it uses some useful functions and techniques that have a wider use and that the average user might not be aware of.
The RasterTiler
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Above: RasterTiler Example Workspace.
The workspace reads a CDED format DEM, tiles it and converts to GeoTIFF.
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Above: This close-up of the RasterTiler highlights there are two rows and columns to be created.
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Above: The feature counts show how one image has been split into four (a 2x2 grid).
File Naming
By default the output from this process would be a series of files bearing the same name as the source data.
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Above: The default output files.
However, the RasterTiler outputs a row and column number which we can combine with the Concatenator to produce a new output filename.
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Above: Concatenator settings dialog.
By default filenames are obtained from the source format attribute fme_basename using a feature type fanout on that attribute. Therefore a new filename is applied by simply changing the fanout to use the new concatenated name attribute.
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Above: Updated fanout setting.
When the fanout is applied like this the output files are named using our newly created attribute.
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Above: Filenames Created from Concatenated Attribute.
Viewing the Output
The output can then be opened in the FME Viewer to be inspected.
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Above: When opening multiple GeoTIFF files an option exists to divide the data up by filename.
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Above: This option produces a single feature type (layer) per filename.
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Above: The output shows clear evidence of being tiled into four quarters.
NB: The differences in colour range in the above images are caused by the Viewer calculating a scale separately for each raster. This only occurs because these are numeric rasters which need colour interpretation to be viewed: the underlying data is perfectly correct! Colour rasters would not exhibit the same differences because they would not need special interpretation. If you wanted to visualize this data as a continuous surface you could add a RasterInterpretationCoercer to the workspace before the RasterTiler to coerce everything into Grey8 (as opposed to Int8) - however refining the display like this would render the data useless as a DEM!
