FME Transformers: 2024.1

Categories
3D
Rasters
Related Transformers
RasterAspectCalculator
Scaler

# RasterSlopeCalculator

Calculates the slope (maximum rate of change in z) for each cell of a raster.

### Typical Uses

• Calculating slope on elevation rasters
• Calculating the rate of change on raster band values

## How does it work?

The RasterSlopeCalculator receives raster features, and calculates the slope for each cell.

Slope may be measured in either Degrees (0 to 90), or Percent Rise (0 to infinity). 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.

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

For multi-band rasters, each band is processed separately, with slope values calculated for each band on each cell. To restrict operation to specific band(s), use a RasterSelector prior to the RasterSlopeCalculator.

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

### Z Factor, Scaling and Units

Input rasters’ horizontal (x and y) units are expected to be the same as vertical (z) units.

If this is not the case - for example, if the horizontal units are in meters with elevation (z) in feet (or any other similar unit type mismatch), you may apply a scale factor (also known as Z Factor) with the Scaler transformer prior to using a RasterSlopeCalculator.

In this example (ground units are meters, elevations are feet), the scale factor to use is 0.3048 - the number of meters in one foot.

If the ground units are lat/long, the appropriate scale factor will vary greatly between the equator and the poles. In this case, consider reprojecting the input raster with a Reprojector, to an appropriate coordinate system with ground units matching the vertical (z) units.

## 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).

## Editing Transformer Parameters

Transformer parameters can be set by directly entering values, using expressions, or referencing other elements in the workspace such as attribute values or user parameters. Various editors and context menus are available to assist. To see what is available, click beside the applicable parameter.

## Reference

 Processing Behavior Feature Holding No Dependencies None Aliases History

## FME Community

The FME Community is the place for demos, how-tos, articles, FAQs, and more. Get answers to your questions, learn from other users, and suggest, vote, and comment on new features.

Search for all results about the RasterSlopeCalculator on the FME Community.

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