Attempting to re-interpolate the nav/scan timing on CASI data for flight 97/14 using aznav, the program seems to edit the HDF files correctly but then doesn't release the file lock (gives error "There are still open AIDs" on closing). Everything seems fine but then it causes azgcorr to hang part-way through. It is believed this is because the old data is HDF 3.3 format (rather than HDF 4) and there are compatibility problems.

Descriptive email from Ben to Bill (4/Mar/2009):

We were (still) trying to track down our Vocals offset problem and we think we stumbled across something else. We used CaliGeo to process a line that had had a timing error in it when we'd processed it using the az suite, and CaliGeo didn't produce a timing problem.

We noticed that in the bit where Caligeo is looking for sync the message it finds has a time delay of 548ms, which matches the 548 in the "Navsync Timing" line on the line 5 header file. The previous sync message it found (and discarded) had a time delay of 119ms, which matches the Navsync Timing for line 4. Azimport for that line found a specim sync message offset of 0.119, which suggests to me that it actually picked up the sync message for line 4 rather than 5. Can you take a look at this when you get a chance please? Let me know if I can send you any additional test data. 

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