Some Hawk bands are noisy to the point of uselessness. For example band 71 (1403nm), raw data from Nigg Bay line 3 (attached)

Also see over-water spectrum produced in level 3 image:

Spectrum cannot really be used for anything much - there is no means of quality controlling the data

Data issue occurs over more than one flight, possibly there are sensor problems with some Hawk bands. See eg. Latera band 71, similar to Nigg Bay:

If you plot Eagle and Hawk processed output on the same graph (see attachment) there's about a 30nm overlap for the spectral range, and the instruments don't seem to agree in this overlap. Even if the instruments don't give the same magnitude, the absorption features shown should align (and they don't). This suggests that the spectral calibration of one or both instruments may be out by up to 100nm, which appears to be the displacement needed to make the two graphs align.

Processing data in azspec and using the -dIc option to rescale dark frames seems to cause the data to be incorrectly radiometrically calibrated.

I've attached three screenshots. dIc_ex1.png shows spectral profiles for the rescaled flightline from both azspec (top) and CaliGeo (bottom). You can see that the azspec spectrum goes up at both ends, where the CaliGeo spectrum doesn't. The azspec spectrum also has values that are consistently about 600 higher than CaliGeo (discounting the edges of the spectrum, which as mentioned are much higher).

dIc_ex2.png shows spectral profiles from the second flightline, which did not require the dark frames to be rescaled. Azspec and CaliGeo are in very close agreement for this line.

odd_one_out.png is just for illustration - it shows all of the Eagle lines from that flight (as processed through azspec) overlaid. The first flightline (with the rescaled dark frames) is clearly visible as different - much whiter than the other lines.

This may affect any datasets from 2006, and some VOCALS data.

Related tickets: #218 #250