Reading ArcASCII / ArcGRID doesn't handle NODATA value correctly - or I don't
understand the concept
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Key: GEOT-3279
URL: http://jira.codehaus.org/browse/GEOT-3279
Project: GeoTools
Issue Type: Bug
Components: gc arcgrid
Affects Versions: 2.7-M3, 2.6.5
Reporter: Stefan Alfons Tzeggai
Assignee: Simone Giannecchini
Priority: Minor
Attachments: NODATA_ArcGridVisualizationTest.java.patch
Since I switched Geopublisher and AtlasStyler from GT 2.3 to GT 2.6 a long time
ago, we always had problems with NODATA and transparency in ArcASCII files. Our
quick solution at that time was to continue to use the old ArcGridRaster class
which worked fine to create GridCoverages. My plan for GP 1.6 is to used only
readers, so I looked into the problem again.
I wrote two tests that load an ArcASCII dataset
(SWAN_NURC_LigurianSeaL07_HSIGN.asc) and look at it's NODATA value. My
understanding is, that when the "coverage/raster/image driver" is aware of a
NODATA value being defined, that that NODATA value should not appear in the
coverage. The tests show that the NODATA value appears in the coverage and in
the image just like a normal value.
In my understanding, NODATA values are workarounds for data-formats that do not
support null values. Once they are identified, they should be replaced with
null or NaN so that any statistics or styling done on the data ignores them.
Please, can someone look at these two tests and tell me whether I found two
bugs or whether I just do not understanding the concept of NODATA values
correctly. Thanks.
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