Hi Peppe and others,
OJ doesn't understand no-data (in terms of registering -9999 and
converting it), as you can also see when colour theming vector data with
classification (it is not possible to exclude certain values).
I believe I personally tried to use also unrealistic values such as the
-9999 in implementations. But, as there is/was no OJ standard, it is up
to the plugin author. So, its probably a bit messy at the moment.
However, I guess Sextante has a standard on it?
Btw. for vector attributes I also tried using "Double.NaN" for null or
in-valid values, which is not possible everywhere (e.g. one needs to
know that it is Double value).
Perhaps we should/can define amn OJ standard on that? However, the
problem comes then also with writing the data. I.e. when you give the
data to someone with his own program...
Perhaps Jukka knows a about how other programs handle this?
cheers,
stefan
On 02/25/2015 10:38 AM, Giuseppe Aruta wrote:
Sorry, I forgot the core argument: I was talking about TIFF images
loaded by RasterImageLayer.class ( so called "Open Sextante Raster Image"
Peppe
2015-02-25 11:56 GMT+01:00 Giuseppe Aruta <giuseppe_ar...@yahoo.it
<mailto:giuseppe_ar...@yahoo.it>>:
Hi,
I use OJ/Sextante for spatial analysis on DEM. And recently I
wanted to extend OJ raster capabilities to make it more flexible.
In some occasion I checked that OJ doesn't handle NonData value
very well, for instance a)on displaying on workbench or b) on
querying raster info, ex.using the new tool Raster>Raster
statistics {Which I made :-( } .
In several times OJ reads NoData value as the minimun value - it
is the experience of the user to understand and try to solve it.
Grid files have not such problem (FLT or ASC, handled by OJ) as
NoDat is written into the headers.
How does OJ handle nodata values?
Does OJ recognize only the standard ESRI -9999 value or even any
other arbitrary nodata values (SAGA -999999? In may occasion I
found elevation DEM where the nodata value was set to 0, you can
understand when this DEM are used for slope or aspect maps!)?
Can we handle nodata on TIFs, maybe using the auxiliary XML file
(thanks Alberto's job)?
Thanks in advance for the answer. It would be fine for me if I
have a help.
Giuseppe Aruta
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