An ECW (Enhanced Compression Wavelet) is a file format in which orthomosaics have been put next to each other and can be viewed as one picture.  The process of stitching these pictures together is carried out by high-quality software and monitored manually.

ECWs are used to work within the pictures of a certain area quickly and conveniently ECWs are supported by a wide range of software packages and GIS and CAD applications.