Raster Pyramiding Example

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The attachment 'RasterPyramidingExample.zip|attached workspace' not found shows an example of raster pyramiding using FME.

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The Workspace

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Above: Raster Pyramiding Example Workspace.

This workspace reads a single large raster image, pyramids and tiles it, and writes the output to GeoTIFF.

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Above: This close-up of the RasterPyramider highlights that the smallest raster will be 24x24 pixels in size.

So the first raster to be created will be resampled to be 24x24 pixels in size. Each subsequent raster will be twice the resolution giving 48x48, etc...

When the size of the original raster is reached then the pyramiding process stops.

In this example the original raster size is 1201 x 1201 pixels. The smallest raster will be 24 x 24. Therefore the raster pyramids will be...

24 x 24
48 x 48
96 x 96
192 x 192
384 x 384
768 x 768
1536 x 1536

...giving a total of seven pyramid layers.

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Above: The feature counts show how the one image has been split into seven layers.

An ExpressionEvaluator is used to determine how many tiles to create for each pyramid layer. The RasterTiler then does the tiling. In this example we use the simple formula:

<numberOfTiles> = <totalNumberOfLayers> - <layerNumber>

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Above: The ExpressionEvaluator Settings.

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Above: The RasterTiler Settings.

So with:

<totalNumberOfLayers> = 7

We get:

7 - Layer 6 = 1 (i.e. 1x1 tiles)
7 - Layer 5 = 2 (i.e. 2x2 tiles)
7 - Layer 4 = 3 (i.e. 3x3 tiles)
7 - Layer 3 = 4 (i.e. 4x4 tiles)
7 - Layer 2 = 5 (i.e. 5x5 tiles)
7 - Layer 1 = 6 (i.e. 6x6 tiles)
7 - Layer 0 = 7 (i.e. 7x7 tiles)

So the total number of output files will be:

(1x1) + (2x2) + (3x3) + (4x4) + (5x5) + (6x6) + (7x7) = 140

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Above: This number is borne out by the FME log file...

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Above: ...and by the Feature Connection counter.

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Above: So in this animation we can see that the coarsest (first) layer has only one tile, but by the finest (seventh) layer there are 7x7 tiles.