[Qgis-user] NoData

[Matt Boyd]

I can contribute a couple of things from my experience with some of these.
1. there are some gotchas with using NULL (in vector files) is that the
result of X+NULL or X concatenate NULL, effectively any operation using
NULL the result is NULL. This is expected/deliberate.
I've only come across Nan in tiffs when there's somethings wrong with the
format / import.
Nodata seems to be specified, the default is set at 0 on most files/formats
I've dealt with (usually single band rasters) and its handled the same way
as if I specify -999.

Matt



On Wed, Oct 15, 2014 at 10:39 AM, Bernd Vogelgesang <
bernd.vogelgesang at gmx.de> wrote:

>  This post seemes to have drowned, so I dare to bump it, hoping that some
> less confused people like me might anwser to it.
> I'm using QGIS for years now, but I never figured out how that stuff is
> supposed to work.
> One of the reasons why I try to do a lot of stuff now in R is that NA is
> NA !
>
> Am 08.10.2014, 11:27 Uhr, schrieb Niccolò Marchi <
> sciurusurbanus at hotmail.it>:
>
> hi all!
> please, is there someone who could explain properly all the "NoData topic"?
>
> I mean:
> 1. differences in setting negative values (-999, -9999, -3.40282e +35,
> etc) VS NoData (Nan, NoData, NULL)
> 2. how QGIS handles it
> 3. "best practices" or good hints for managing them
>
> sorry but I've quite a big confusion.
>
> Thank you very much in advance!
>
> Nic
>
>
>
>
> --
> Bernd Vogelgesang
> Siedlerstraße 2
> 91083 Baiersdorf/Igelsdorf
> Tel: 09133-825374
>
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