Calculates the aspect (direction of slope) for each cell of a raster. Aspect is measured in degrees from 0 to 360, clockwise from north.

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Typical Uses

  • Calculating aspect on elevation rasters

How does it work?

The RasterAspectCalculator receives raster features, and calculates the aspect for each cell.

Aspect is calculated in degrees, from 0 to 360, clockwise from north. The calculation is done based on the values of surrounding cells (using a 3 cell x 3 cell window), and a choice of algorithms is available. Cells without data (Nodata) may be interpolated for calculation purposes. If an input band does not have a Nodata value, the output band Nodata value will be set to -1.

Aspect values are output on the same band they were calculated from, and the band is converted to Real64.

This transformer supports raster band selection. The RasterSelector can be used to modify this selection.


Usage Notes

Choosing a Raster Transformer

FME has an extensive selection of transformers for working with raster data. They can be generally categorized as working with whole rasters, bands, cells or palettes, and those designed for workflow control or combining raster with vector data.

For information on raster geometry and properties, see Rasters (IFMERaster).


Input Ports

Output Ports


Editing Transformer Parameters

Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.

Dialog Options - Tables

Transformers with table-style parameters have additional tools for populating and manipulating values.


Processing Behavior


Feature Holding


Dependencies None

FME Community

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Examples may contain information licensed under the Open Government Licence – Vancouver and/or the Open Government Licence – Canada.