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 attached workspace 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
Above: RasterTiler Example Workspace.
The workspace reads a CDED format DEM, tiles it and converts to GeoTIFF.
Above: This close-up of the RasterTiler highlights there are two rows and columns to be created.
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.
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.
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.
Above: Updated fanout setting.
When the fanout is applied like this the output files are named using our newly created attribute.
Above: Filenames Created from Concatenated Attribute.
Viewing the Output
The output can then be opened in the FME Viewer to be inspected.
Above: When opening multiple GeoTIFF files an option exists to divide the data up by filename.
Above: This option produces a single feature type (layer) per filename.
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!
