On Wed, Oct 21, 2015 at 4:46 PM, Smart, Gary Export License Required - US
UTAS <Gary.Smart@anonymised.com> wrote:
Using gdalwarp, the corners are indeed populated (thanks guys) – even when
converting from a NTF directly to another NTF.
Converting to geotifs using gdalwarp also rectifies the image of course.
When mosaicked into geoserver, the alignment to the underlying map is not
precise, but I kind of expected this since IGEOLO precision in the NITF
standard is pretty poor. The warping applied to the files by gdalwarp
appears to be the same as that applied by the mosaic plugin on the raw
geotif inputs I used before i.e. it would appear acceptable to pass non
rectified imagery to the imageMosaic plugin and it presumably gdalwarps it
for you.
A couple of interesting points worth noting that I’ve spotted en-route:
1) With 16bit imagery, applying the transparency colours to zero in
the layer preferences for a mosaic, turns the whole image transparent. I’m
guessing that someone somewhere is assuming all inputs to the mosaic are
8bit?
2) gdalwarp –of NITF –s_srs EPSG:4326 –t_srs EPSG:4326
myOriginalFile.ntf myNewFile.ntf fails to embed the georeferencing into
the IGEOLO, giving the following errors:
ERROR 6: NITF file should have been created with creation option
‘ICORDS=G’ (or ‘ICORDS=D’).
The IGEOLO field contains 4 coordinates to provide summary info of the
bounding box of the dataset.
I said "summary" since, as you said, the IGEOLO field shouldn't be used to
get a precise representation of the Georeferenced area. NITF supports
dedicated TREs (Tagger Record Extensions) to contain more detailed
georeferencing info.
Depending on the CRS it can be expressed as both decimal degrees or
degrees,minutes,seconds for geographic CRS or meters for UTM CRS,
More details in the specification:
http://www.gwg.nga.mil/ntb/baseline/docs/2500b/2500b.pdf
I have never tried gdalwarping a NITF to a NITF but I think that the GDAL
utility expects some guidance from the user through the "Creation Options".
If you run "gdalinfo --format NITF" it will report all the supported create
options. (ICORDS is one of them and I think you have to provide it). You
also probably have to specify more of them depending on the ERROR messages
GDAL is reporting until it finally creates the output.
as an instance:
gdalwarp -of NITF -s_srs EPSG:4326 -t_srs EPSG:4326 -co
"ICORDS=D" myOriginalFile.ntf myNewFile.ntf
Daniele
ERROR 6: Apparently no space reserved for IGEOLO info in NITF file.
and dumps an aux.xml file instead – presumably not used by Geoserver which
crashes immediately on publishing such mosaicked NITF layers with:
java.lang.RuntimeException: Error occurred while building the resources
for the configuration page which is ultimately ‘caused by’ No
Transformation available from System”EngineeringCRS[Wildcard 2D Cartesian
plane in metric unit] to GeographicCRS[WGS84(DD)]
…which is fair enough I suppose!
--
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