NumericRasterizer

Creates a numeric raster representation of vector or point cloud input features, where cell values are taken from the z coordinates of the input features and overlaid on a uniform background.

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Typical Uses

  • Creating single-band numeric raster representations of vector data
  • Rasterizing vector polygons as a precursor to raster algebra
  • Not used for generating DEMs or overlaying vectors on an existing raster

How does it work?

The NumericRasterizer receives point, line, area or point cloud geometries, and “draws” them onto a numeric (single-band) output raster feature.

Input features must have z coordinates. The cell values for the rendered input features are taken from their z coordinates, and the remainder of the raster is filled with a single specified Background Value, which may also be designated as the raster band’s Nodata value.

The size of the output raster may be defined by number of rows and columns, or by specifying the size of a single cell (pixel) in ground units. The geographic extent covered by the raster may be either determined by the input features or manually specified.

A variety of options is available for raster interpretation type. Anti-aliasing may be used to smooth lines.

The input features are discarded.

If vector features (such as polygons) overlap, then the value of the cell in those overlaps comes from the last feature to arrive.

Rendering non-elevation values: 3DForcer

Vector features often represent non-elevation data. To produce a numeric raster representation of those vectors with a NumericRasterizer, the value to be represented needs to be stored in the z coordinate of the source data.

To accomplish this, use the 3DForcer transformer prior to the NumericRasterizer, and assign the desired values to the features’ z coordinates.

Examples

Usage Notes

  • To rasterize vector or point cloud features into a color raster, consider using the ImageRasterizer or MapnikRasterizer.
  • The NumericRasterizer does not interpolate cell values as might be required when using point-based features such as elevations or weather stations. If interpolation is required, consider using the RasterDEMGenerator, DEMGenerator, or SurfaceModeller.
  • To carry out raster algebra on rasterized polygons, use either the RasterExpressionEvaluator or RasterCellValueCalculator transformers.
  • To rasterize vector data onto an existing raster feature, consider using the VectorOnRasterOverlayer or MapnikRasterizer.
  • When rasterizing point clouds, all points are processed, in the order they occur within the point cloud. Depending on the resolution of the raster, multiple points may fall within a cell. As all are processed, the last point encountered within a cell will provide the band value. The PointCloudSorter may be useful to prepare the point cloud.

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).

Configuration

Input Ports

Output Ports

Parameters

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.

Reference

Processing Behavior

Group-Based

Feature Holding

Yes

Dependencies None
Aliases  
History  

FME Community

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