[GRASS-user] Null or 0?

[Daniel Victoria]

Hi Andre,

On raster algebra, operations using null will return null while operations
with 0 behaves like expected. Ex:
12 x null = null
12 x 0 = 0

Null is interesting to use on areas you don't have / want to represent,
like an ocean...

Hope it helps
Daniel
On Feb 5, 2012 12:03 AM, "ALT SHN" <i.geografica at alt-shn.org> wrote:

> Hello,
>
> I have a technichal doubt. I used* v.to.rast.constant *to tranform a line
> vector layer to raster. This meant i have a raster with NULL values.
> The output raster is to be used in map algebra operations.
>
> So my question is:  Is it advisable to set the Null cells to 0? I know
> r.calc works with NULL values, and I know that NULL is not the same as 0,
> however I never understood what difference does it make if any. Considering
> these two scenarios what do I win and what do I loose?
>
> Any enlightening will be very aprecciated!
>
> Thanks,
>
> André Mano
> ---------------------------------------------------------------
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>
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