ECW (file format)

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Enhanced Compression Wavelet
Filename extension .ecw
Type code C / C++
Developed by ERDAS
Initial release 1998
Latest release 4.2 March 2011
Type of format Image file format
Website http://www.erdas.com/

ECW (Enhanced Compression Wavelet) is a proprietary wavelet compression image format optimized for aerial and satellite imagery. It was developed by Earth Resource Mapping, and is now owned by ERDAS, which is owned by Intergraph.[1] The lossy compression format efficiently compresses very large images with fine alternating contrast.

In 1998 ER Mapper, Ltd (Perth Australia) company founder Stuart Nixon,[2] and two software developers Simon Cope and Mark Sheridan were researching rapid delivery of terabyte sized images over the internet using inexpensive server technology. The outcome of that research was two products, Image Web Server (IWS) and ECW. ECW represented a fundamental mathematical breakthrough enabling Discrete Wavelet Transforms (DWT) and inverse-DWT operations to be performed on very large images very quickly, while only using a tiny amount of RAM.[3] For ECW patents, see US 6201897  and US 6442298 . For IWS patent, see US 6633688 . These patents were assigned to ERDAS (under a former name of Leica Geosystems Geospatial Imaging) July 29, 2007.

After JPEG2000 became an image standard, ER Mapper added tools to read and write JPEG2000 data into the ECW SDK to form the ECW JPEG2000 SDK. After subsequent purchase by ERDAS, the software development kit was renamed to the ERDAS ECW/JP2 SDK.

Contents

[edit] Properties

Map projection information can be embedded into the ECW file format to support geospatial applications.

Image data of up to 65,535 bands (layers or colors) can be compressed at a rate of over 25 MB per second on a i7 740QM (4-cores) 1.731 GHz processor using v4.2 of the ECW/JP2 SDK. Data flow compression allows for compression of large images with small RAM requirements. The file format can achieve typical compression ratios from 1:2 to 1:100.

The ECW Protocol (ECWP) is an efficient streaming protocol used to transmit ECW and JPEG2000 images over networks, such as the Internet. ECWP supports ECWPS for private and secure encrypted streaming of image data over public networks such as the Internet.

There is a very fast read-only SDK supporting ECW and JPEG2000 which is available for no charge for desktop implementation (Microsoft Windows only). The read / write SDK is available for desktop and server implementations, but are not free. A full functioning server implementation (using ECW, JPEG2000, ECWP and JPIP) is available with an ERDAS APOLLO IWS license.[4] A previous version of the SDK (3.3) is available in open source, and can be used for non-Microsoft operating systems, such as Linux, MacOs or Android.

[edit] Packages offering support

The software packages offering support include:

[edit] References

Cadcorp SIS and Cadcorp GeognoSIS.NET Website

  1. ^ http://field-guide.blogspot.com/2010/07/hexagon-aquires-intergraph.html Retrieved Aug 19, 2011
  2. ^ nearmap
  3. ^ http://www.gisdevelopment.net/interview/previous/ev022.htm Retrieved Feb 21, 2010
  4. ^ http://www.erdas.com/products/ecw/ERDASECWJPEG2000SDK/Details.aspx

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