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Ticket Resolution Summary Owner Reporter
#2 fixed Support: 15/May/2007, Rachel Gaulton, GB06/05 mggr mggr

Two issues:

  • Amer checking on LIDAR.
  • Use of bsq with azgcorr
    • mggr suspects perhaps the missing scans are throwing off the navigation?

Rachel's initial contact email:

I am trying to process ATM and CASI data flown last summer over my two
sites in Wales (GB06/05, PI - Tim Malthus). Unfortunately we are
having a few problems with AZGCORR and I wanted to check whether you
had encountered them before and had any idea what might be wrong (or
who else might have).

As we are carrying out atmospheric correction before geometrically
correcting the swaths in AZGCORR, so we are using the resulting .bsq
image in conjunction with the original .hdf (and a DTM) as inputs to
AZGCORR, as recommended in the user guide. With the CASI data and most
of the ATM swaths this appears to work ok (at least as far as can be
determined by visual inspection of the results), however with certain
swaths the geometric correction is not successful. These seem to be
swaths with considerable numbers of missing pixels / scan lines.  When
the raw .hdf data is geometrically corrected directly, the problems do
not appear and AZGCORR  works correctly (attached jpeg1), but when the
image is first converted to .bsq and atmospherically corrected the
image seems to be corrected up until the point of the missing scan
lines, but after that appears to be just 'stretched' to fit the
correct outline (jpeg2). The same problem is also being encountered by
John Dowens in correcting strips from GB06/07.

Do you have any ideas what may be causing this problem? Any
suggestions very much appreciated.  I was also wondering if you know
when I might be likely to receive the remaining LIDAR data from this
acquisition (I have the lidar from my Glasfynydd site but not from

jpeg1 from Rachel's initial email

jpeg2 from Rachel's initial email

#9 fixed BSEQ dump produces incorrect ENVI header mggr mggr

azexhdf -h a195041b.hdf -BSe a195041b_test.raw

Should produce an envi .hdr for a bseq file (azexhdf help states:

  -B  fn      : convert image data to BIL binary file
  -BS fn      : convert image data to BSEQ binary file
  -Be fn      :
  -BSe fn     :
              :  B and BS may be followed by  e  to request an ENVI
              :  compatible header to be output with extension fn.hdr
              : For ENVI compatibility fn should be given as  fn.raw or fn.bil
              : fn  = output filename

Actual header file produced claims it's a BIL, not a BSEQ: arsf@pmpc889:~/support/20070515-GB06_05-195a-RachelGaulton<1040>cat a195041b_test.hdr

description = { File output by azexhdf }
file type = ENVI
interleave = bil
samples = 938
lines = 3802
bands = 11
header offset = 0
data type = 12
byte order = 0

Correcting the interleave line to read "bseq" results in a correct load into ENVI.

#10 fixed Access to OS vector overlays mggr mggr

Currently obtained via requests to Andrew Wilson.

We may be able to gain access via the Pan-Government Agreement, according to Tony Clifton @ BGS. We need to sign up at to see if we're eligible.

Steve is doing this.

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