When the former ER Mapper, Ltd (purchased in May 2007 by ERDAS) began work in 2003 to add support for JPEG2000 (JP2) to the ECW SDK, ER Mapper noticed JP2 specifications were very broad. As a result, JP2’s speed would not approach ECW speeds for decades, if ever. Think of it this way, JP2 is a Sports Utility Vehicle (SUV or 4-wheel drive) and ECW is a Formula 1 Ferrari.
The geospatial industry deals with dozens to thousands of images at a time and speed is critical. While geospatial users need the Formula 1 Ferrari, they must drive on public roads (lowest common IT standards), and thus must use the SUV not the Formula 1.
How can SUV owners get more speed from their JP2 beast? By using the ERDAS ECW/JP2 SDK’s J2I file. This ‘index’ file to the JP2 file allows customers to more rapidly access JP2 data in a viewing technology that uses the ECW SDK to read ECW and JP2 files. The J2I file will significantly improve your performance by fine tuning your existing engine.
The improvement in speed depends on the encoding method. Some encoding methods mandated by less geospatially sophisticated IT departments are like pulling a loaded trailer behind the SUV. An engine tuning helps, but slow starts cannot be avoided.
You may ask, how do I create these on JP2 J2I files in ERDAS IMAGINE 2010? For one image at a time, just touch the file with any ERDAS IMAGINE function, and like the aux file, it is automatically created.
For batch creation, use the Edit Image Metadata (aka Image Command Tool). Select one image needed, select ‘Batch’, the select all images needed in the batch tool.
You may be asking, why is there no check-box function for creation the J2I file on Edit Image Metadata? All you need to do is touch the file with any ERDAS IMAGINE function and it is created. Thus only touching the file in Batch Mode is needed.
And with the IMAGINE Advantage 2010 batch mode, you can touch up to four images at a time with each IMAGINE Advantage floating license you have available.
Back to our cars (image file formats); what I want from my GIS and remote sensing data format and software is a street version Ferrari (has a roof, stereo, leather seats, electric windows, air-conditioning, and of course GPS).
Ref: What are J2I files? and Why compress?
See info on the latest ERDAS ECW/JP2 SDK.