Dear Andrea,
On 10 February 2016 at 18:22, Andrea Aime <andrea.a...@geo-solutions.it>
wrote:
> [SNIP]
> Does GeoTiff have statistics built in? First time I hear about it?
> Or are you talking about the GDAL statistics file (a xml file normally),
> which is not part of any standard?
> Indeed the code is not making any effort to read it.
>
>
I think you are right, it is not stored within the geotiff itself, but on
auxiliary files (the one generated by GDAL or other ones).
> When you talk about statistics do you mean just min and max, or an
> histogram?
>
Min, max, and maybe mean and standard deviation.
> And where would you expect to see the results of this calculation? Right
> now I believe they are showing up only in WCS outputs as far as I know
> (and assuming you're not talking about a histogram, which won't show up
> anywhere).
>
They are currently stored on the coverage data (you can modify them on the
interface) and available on the API REST. They are useful to generate some
kind of legends.
>
>
>>
>> c) Geoserver apparently is not able to compute raster statistics from the
>> data source
>>
>
> It is not indeed, but it has the machinery necessary to do it. What is
> worrysome about it is that some data
> sources are several terabytes of data (or more), calculating full
> statistics on them might require hours or days.
> Seems like a job for a WPS process, that can be called asynchronously, at
> least for large datasets.
>
Yes, maybe WPS is more appropriate. In any case, if it is not triggered
automatically but by a specific parameter it should not be so worrisome.
Best regards,
Cesar
>
>>
>> We intend to correct a) in the sort term (meaning: now), but we might
>> also be interested on b) and c) on the long term depending on the required
>> effort.
>>
>> For c), I envisage a parameter on REST requests for coverages which
>> forces the (re)calculation of statistics. For instance:
>> POST /workspaces/<ws>/coveragestores/<cs>/coverages[.<format>]?stats=yes
>> (when uploading the coverage)
>> GET
>> /workspaces/<ws>/coveragestores/<cs>/coverages/<c>[.<format>]?stats=yes
>> (for an already published coverage)
>>
>> Do you think it could be a good approach?
>>
>
> For small datasets yes, for larger ones a synchronous request might take
> too much time
>
> Cheers
> Andrea
>
> --
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--
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César Martínez Izquierdo
GIS developer
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