The SIHI contains more information than stored in the corresponding low-dispersion file and, as a result, the FITS format is slightly more complex. Overall, the SIHI is comprised of a primary array containing the resampled image, a binary table of wavelengths and both predicted and found line positions, an image extension of flags, and a second image extension of background cosmic ray flags.

The high-dispersion SI data is similar to the low-dispersion SI data except that the high-dispersion wavelength linearization varies with spectral order, and the entire image is stored in the primary array. Each pixel is resampled to the position determined by the summation of the vectors computed for:

- shift to photometric correction (ITF) raw space,
- shift from ITF space to geometrically-rectified space,
- rotation such that orders are horizontal,
- wavelength linearization,
- adjustment to maintain the echelle orders at approximately the same locations in the file in the spatial direction,
- corrections for the spatial deviations (cross-dispersion wiggles) for LWP, LWR, and SWP data,
- heliocentric velocity correction, and
- de-splaying correction.

Because the wavelength linearization varies with spectral order, the starting wavelength and wavelength increment values vary with each order. This information is stored in a binary table extension to the SIHI, which follows the primary array. The entire contents of the binary table extension include:

- Order Number, one 8-bit integer.
- Starting wavelength, one double-precision floating point number. Heliocentric velocity correction has been applied.
- Wavelength increment, one double-precision floating point number.
- predicted line position of order centroid, one single-precision floating point number.
- line position where spectral centroid is found, one single-precision floating point number. (This is determined by the high-dispersion spectral flux extraction module and written back into the SIHI file retroactively.)