Determining the Block Size For NITF Files

Question: 

How does ENVI determine the block size that it uses when writing NITF format files?

Answer:

When writing NITF files from the ENVI interface, the block size that is used depends on the dimensions of the image.  If the number of rows and columns is less than 4096, the block size is set to the full image size. For larger images, the image is set to a block size of 1024 x 1024.

The only exception to this is if you choose to write the NITF file with JPEG2000 compression. In that case, the file will always have a block size of 1024 x 1024.

It is necessary for ENVI to follow these rules to make sure that the NITF 2.1 files are compliant with the NITF standard.

 

reviewed 8/28/14 PS & KK