Filling out the ENVI Header Info dialog fields for non-georeferenced AVIRIS data

 

Non-georeferenced AVIRIS data are distibuted by JPL in a flat binary format without a header. When a user attempts to open the data in ENVI, they receive a dialog box prompting them to enter pertinent header information so the data can be displayed correctly. This article outlines how to fill in the Header Info fields.

The .readme file that comes with AVIRIS data provides the parameters you will need to input. Non-georeferenced AVIRIS data almost always have a BIP interleave, an IEEE byte order, contain 614 samples and 224 bands, have a 0 offset, and Integer format. The number of lines will vary depending on the file you are trying to open. To find out how many lines there are in a scene take the size of the file in bytes and divide it by 275072.

For example, the following steps could be carried out:

1. Find the file size on disk = 140,836,864 bytes (on Windows, right click on the file and choose Properties to obtain this number).

2. Divide by the number of samples per line (614)

3. Divide by the number of bands (224)

4. Divide by the number of bytes per pixel (2)

The result is 512 lines in this example.

Most AVIRIS flight lines are broken down into 614 sample x 512 line pieces, but this is by no means set in stone, so it's a good idea to check using the above process when attempting to open AVIRIS data in ENVI.

Note that in the new ENVI interface (from ENVI 50) you would need to open the file from the following Toolbox menu: /Raster Management/Edit ENVI Header - Then select Open > New File in the interface.

Upon opening the file, you might see a lot of distortion if you are working with low altitude (approx. 5m) data. For the data to "look" good, you should apply the Geographic Lookup Table (GLT) that comes with the data.

- In ENVI Classic go to: Map->Georeference from Input Geometry->Georeference from GLT.

- In ENVI select: /Geometric Correction/Georeference from GLT in the Toolbox

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Reviewed by BC on 09/05/2014