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Ticket Resolution Summary Owner Reporter
#108 fixed Support: 28/Mar/2008, Chris Hecker, WM06/06 mggr mggr
Description

New contact from Chris with some atmospheric correction questions (note #42 for previous support)

Hi Mike;
 
after a few months of radio silence, I have a question for you again! ;-)
 
I am wanting to do atmospheric correction on the 2006 Mojacar Eagle and Hawk data with ATCOR4 ( http://www.rese.ch/atcor/atcor4/index.html). For that I need to also input
- a sun elevation and sun azimuth file (which I should be able to do with some freeware software)
- a scan angle file  with the viewing vector for each pixel (azimuth angle, zenith, angle, height of plane).
 
Gary mentioned that you may be the person best suited to judge which workaround or tool from the user community is available for that. He mentioned that Matt Disney from London had retro-engineered the info in the past for BRDF studies.
Do you know anything about that and are these tools(?) available?
 
 
The other question is about the metadata info in the hdf file.
 
I presume that folder "Navigation" contains info from the plane's IMU (NVhead, NVpitch NVroll), and GPS (NVlat NVlng NVhgt)
 
and that the folder "Coordinates" contains info from a ?second IMU (COhead, COpitch COroll) and a ?second GPS (COlat, CO lng, COhgt) which are positioned near the instruments.
 
Is that correct? What do the values in COqual represent? Do you have a document that explains the different tags in the hdf file? That would be ideal.
 
 
Thanks and cheers from Holland,
Chris 

From: Chris Hecker
Sent: Friday, February 22, 2008 4:46 PM
To: 'Gary Llewellyn'
Subject: Info and GLT

Hi Gary;
I have a "couple" of questions. Maybe some are to be forwarded to Phil or somebody else from the processing team.
 
a) did you get the DGPS data from the ftp site? Please let me know when you manage to download the stuff so I can remove it.
b) the Ethiopia SIM card that you gave to me expires in April. I presume you wont need it back. Otherwise let me know.
c) is there a location on the ARSF site where we can see processing progress? I was also wondering if I could find the updated sortie briefs or a shape file that has the final coordinates of all areas flown in the Ethiopia campaign. An ethiopian student was asking me since he wanted to know in what areas hyperspectral data will become available later on.
 
d) this is maye a tricky one. I am looking at the data from 2006 Spain (Mojacar, PI  = Teeuw). I had eventually figured out the geomcorrection with azgcorr. 
Now for the atmospheric correction we want to use ATCOR 4 (programmed by Rolf Richter  DLR and I think Iten from Zuerich). One of the input parameters for the atmospheric correction model is the viewing geometry and distance between plane and each pixel.
this can be supplied either as:
- a geo lookup table (GLT) that defines a map coordinate of each pixel while still in image coordinates
- a scan angle file  with the viewing vector for each pixel (azimuth angle, zenith, angle, height of plane).
 
I looked in the supplied hdf file that accompanies the BIL files. From the coordinate info I should be able to extract the vector for each pixel, but its a lot of work to calculate that.
Do you have a tool that could do this for me? In principle one of the modules of the azgcorr suit has to do a similar calculation for the geocorrection. Is it possible to extract this info ourselves or get it from one of you?
 
What are other people doing about the atmospheric correction of the Eagle and Hawk data? Have you heard any expereinces from other research teams?
#109 fixed Output of ground coordinates in azgcorr mggr mggr
Description

It would be useful if azgcorr could output some extra information on the mapping of points.

Peter Land was interested in level 1 ground coordinates per pixel.

Chris Hecker (#108) has requested per-pixel geocoordinates or per pixel view vector info for feeding into ATCOR, also presumably at level 1. He said ATCOR needed, as an input parameters for the atmospheric correction model, the viewing geometry and distance between plane and each pixel. This can be supplied either as:

  • a geo lookup table (GLT) that defines a map coordinate of each pixel while still in image coordinates
  • a scan angle file with the viewing vector for each pixel (azimuth angle, zenith, angle, height of plane).

Peter contacted Bill about it, who replied (1/May/2007) with:

The option to 3D output pixel coordinates, solar and sensor view
vector details and time are on the cards for Andrew's group to use
with Modtran, so in the not too distant future will be available.
#110 fixed Azspec processed Hawk data has spectral spikes mggr benj
Description

Azspec-processed level 1b hawk data does not appear to be correct - it contains large anomalous spikes in some bands, seemingly correlated to very low data values. Eg from Nigg Bay line 3:

Hawk spectrum from azspec-processed level 1b file over water (8px average)

Compared to Caligeo spectrum from same pixel:

Hawk spectrum from caligeo-processed level 1b file over water (8px average), same place as azspec example

Could be underflowing, but would expect a much higher value for the spikes (~65k) in this case. Might still be underflowing and then changed by maths in azspec though.

Note extended from ticket #106, but separate to Hawk noise issue

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