[Qgis-user] getting statistics from a raster layer

[Antonio Silva]

Thanks Nick and Carlos,

Following the suggestions I got an error message: "Cannot compute bounding
box of cutline." when  cutting the raster. I cannot understand where is the
problem. It happened only with this kind of raster. I tried with nautical
charts and georeferenced maps from Google Earth and I cut them without
problems. Any ideas?

Also I installed SAGA and GDAL. SAGA is great but it will take a time to me
to verify all options.

GDAL - statistic by zones gives part of the answer (count, sum and mean) in
a very convenient way, creating columns at the attribute table.  There's no
need to cut the raster. Nevertheless I need max and min at least. If I
could get max, min, std this way it would be the heaven.

 So, my point now is to cut the raster, or find another tool as "statistic
by zones" with more parameters.


All the best,


Antônio


2012/9/15 Nick Hopton <nhopton at gmail.com>

> I think the first thing to do is clip the raster to your area of interest
> using the vector polygon. Raster -> Extraction -> Clipper. Select the
> polygon shapefile as the mask layer.
>
> To get the statistics load the clipped raster, right-click on it in the
> layers panel, select "Properties" and then click the "Metadata" tab. This
> will show the mean, min, max and SD, but not (unfortunately) the median.
>
> N.
>
>
>
> --
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-- 
Antônio Olinto Ávila da Silva
Biólogo / Oceanógrafo
Instituto de Pesca (Fisheries Institute)
São Paulo, Brasil
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