[Qgis-user] Styles for Extremely Small-Value Rasters

[Michael Treglia]

Nicolas,

Thanks for the quick response. I might be mis-understanding your
suggestion, so let me know if that seems to be the case.

The problem isn't specifying the min/max values (Loading the Min/Max values
from the raster is not a problem). The problem is that the color ramp
doesn't seem to interpret decimals at such fine precision. Since all of the
numbers in the raster are so close to 0, even when I enter specific values
for the color ramp to use (as the 'Value' next to the individual colors),
with such small numbers they all seem to just be recognized as 0.

In case it helps , this is QGIS 2.8.1 Win64 (on Windows 7).

Thanks again!
mike



On Fri, Apr 3, 2015 at 2:13 PM, Nicolas Cadieux <
nicolas.cadieux at archeotec.ca> wrote:

> Hi,
> You can manually place the min and max values. Since the screen is limited
> to 256 values, you will need to decide what values to display.  If 0 is
> null, you should indicate that in the raster properties. That will help
> with the classification.
>
> Nicolas Cadieux M.Sc.
> Les Entreprises Archéotec inc.
> 8548, rue Saint-Denis Montréal H2P 2H2
> Téléphone: 514.381.5112  Fax: 514.381.4995
> www.archeotec.ca
> Le 2015-04-03 14:54, "mtreg [via OSGeo.org]" <[hidden email]
> <http:///user/SendEmail.jtp?type=node&node=5199936&i=0>> a écrit :
>
> Hi All,
>
> I had a raster output from a kernel density estimate I produced in R
> (using the adehabitatHR package). I imported the layer to QGIS, and it
> displays by default without any issue (Rener type: Singleband Gray).
>
> However, when I try changing this to color (Render type: Singleband
> pseudocolor), I can't get the gradient in values to display. Since it is a
> Kernel Density Estimate result, the values are all extremely low, covering
> a fairly large area. The range of values is 0 to 6.4773e-10. When I either
> use the 'Classify' button to set value ranges to specific colors, all of
> the values stay at 0.  When I enter the small values into the
> classification Value field by hand, the display does not change.
>
> Increasing the values by multiplying the layer makes it feasible and plots
> okay, but I'd rather keep values to the originals/not go through an extra
> step.
>
> Anybody have success with plotting rasters with extremely small values
> with different color ramps?
>
> Any suggestions are appreciated...
>
> Thanks,
> Mike
>
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