About ECW and JPEG 2000 formats

ECW is an acronym for Enhanced Compressed Wavelet, a standard for compressing very large images that is widely used in the GIS industry. ECW is an extremely fast data format and is ideal when serving “backdrop” imagery or when imagery is being downloaded by a large number of people.

JPEG 2000 is an ISO standard developed by the Joint Photographic Experts Group (JPEG). JPEG 2000 is a substantial revision of the original JPEG standard. JPEG 2000 provides current and future application features and support, in addition to superior image compression.

Both ECW and JPEG 2000 have their advantages. Choosing which format to use will be based largely on the circumstances that you require them for. To help you make this decision easier, the main factors are summarized below:

Factors to Consider When Choosing the Appropriate Format:

• Serving: If you are intending to serve large amounts of imagery to a large number of users over limited bandwidth, it is recommended that ECW be used.
• Color depth: If you are using imagery with more than 8 bits per channel, you will have to use JPEG 2000. For 8-bit per channel images (RGB, Grayscale, or Multiband), ECW is faster.
• Size: If you are using extremely large datasets (greater than one terabyte), it is recommended that ECW be used.
• Performance: Compression and decompression of ECW images will in most cases be faster than JPEG 2000.
• Lossless: If you intend to use lossless compression, then you will have to use JPEG 2000.
• Interoperability: JPEG 2000 has broad international support because it is an open ISO standard format.
• If serving via a streaming protocol, ECWP is faster, uses fewer resources on the client and server, and is more efficient than JPIP. Both ECW and JPEG 2000 images can be streamed over ECWP; only JPEG 2000 images can be streamed over JPIP.
• If you require images with opacity channels, ECW is faster than JPEG 2000 when serving/viewing these images.

In case the service provides both protocols (ECWP and JPIP), the ECWP protocol will be the default one. Also, the ECW format is superior to jp2. If both formats are available, you can change the protocol format if needed within the controls on the Map Content tab.