RasterGCPSetter

Sets Ground Control Points (GCPs) on a raster, pairing cell positions with known coordinates.

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Typical Uses

  • Specifying georeferencing information for rasters such as scanned maps, surveys, and uncorrected aerial images, based on known positions in the source dataset.

How does it work?

The RasterGCPSetter receives raster features and attaches specified Ground Control Points (GCPs) to them as a raster property.

Each GCP is composed of a pair of positions - the first being a row and column number within the raster, and the second being a known position on the ground, described by a Coordinate System and a set of x,y,z coordinates.

Multiple GCPs may be set with one RasterGCPSetter, and must all be the same coordinate system.

The RasterGCPSetter does not georeference rasters - it only attaches properties that may be used to do so. The GCPs must be applied to the raster to carry out the georeferencing.

A minimum of three GCPs are generally required to georeference a raster. If the raster has already set GCPs, the old GCPs will be overwritten, and so all GCPs must be set in one RasterGCPSetter.

This transformer is unaffected by raster band and palette selection.

GCP Format

Each GCP has five components, separated by spaces:

Column Row X-Coordinate Y-Coordinate Z-Coordinate

For example:

1442 6863 483000 5456000 0

Multiple GCPs are combined into one string, separated by semicolons:

1442 6863 483000 5456000 0;1415 1143 483000 5468000 0;4754 1120 490000 5468000 0

Usage Notes

  • To apply GCPs to a raster in FME, you may use the Apply GCPs parameter in raster format Readers that support GCPs. A RasterGCPApplier custom transformer is also available on the FME Hub.
  • To extract GCP values from a raster, use the RasterGCPExtractor.

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 combing 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.

Reference

Processing Behavior

Feature-Based

Feature Holding

No

Dependencies None
FME Licensing Level FME Professional Edition and above
Aliases  
History  
Categories

Coordinates

Rasters

FME Community

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Examples may contain information licensed under the Open Government Licence – Vancouver

Contains information licensed under the Open Government Licence – Canada.