ER Mapper ECW Reader/Writer

FME supports reading and writing ER Mapper ECW files.


The ECW image format is used to compress very large images, without using intermediate tiling or intermediate disk storage. There is no inherent limitation to image size in the compression technology. However, any image saved in this format must be at least 128 x 128 pixels, and FME usage of the ECW SDK limits image size to less than 1000 gigapixels. Any non-8-bit source data returns an error.

The ECW technique also takes advantage of CPU, L1, and L2 levels of cache to do its linear and unidirectional data flow through the Discrete Wavelet Transformations (DWT) process.

ECW Product and System Requirements



Operating System


FME Desktop License

FME Server

FME Cloud





Available in all FME editions



64-bit: Yes




Available in all FME editions



64-bit: Yes



Reader Overview

FME considers a single ECW file to be a dataset.

The ECW file contains pixel data, and each pixel in the file is a point in a single FME raster feature.

Writer Overview

The writer creates and writes data into a single folder specified by the Dataset parameter. It distinguishes duplicate output files by appending numbers to the filenames.

Usage Notes

  • Many less common coordinate systems may not be properly mapped when writing to ECW files, especially for version 3 ECW files. See Use EPSG Code For Projection for more options related to coordinate system representation. Coordinate system and georeferencing transformations are read, but in some cases coordinate systems may not translate.

  • GCPs (ground control points) present along with a projection in an ECW file being read can either be applied to the data as an affine transformation, or stored as properties of the raster geometry. GCPs cannot be written to ECW.

FME Raster Features

FME raster features represent raster data and use several concepts that are unlike those used in the handling of vector data. The topics below describe how FME processes raster data.

About FME Rasters Tiling and Mosaicking
Raster Properties Band Combining and Separating
Band Properties Band and Palette Selection
Palette Properties Raster Processing
Compression Raster versus Vector Features
Pyramiding Raster File Naming
Interleaving World Files
Interpretation and Data Type TAB Files
Palette Resolution  

ECW supports rasters with an arbitrary number of bands, provided all bands are the same data type and no band has a palette.