Hi John,
thanks for your reply.
The problem I have with this is that I'm setting up a predefined set of
custom CoordinateReferenceSystem definitions:
as an instance, a LambertConformal projection where standard parallels is
25.
Then, I'm parsing the gridMapping attributes in order to try to recognize a
known custom CRS and I'm getting no matches since it is expecting 25
instead of 25.00002. (CRS matching checks use WKT parsing).
In the meantime, I will investigate more on this.
Cheers,
Daniele
==
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On Tue, Apr 21, 2015 at 2:15 AM, John Caron <caron@xxxxxxxx> wrote:
> Hi Daniele:
>
> GRIB projection info is stored in the GRIB file in (at most) 3 bytes, so
> has a maximum precision of 24 bits.
>
> Im surprised that you are seeing a problem, it seems unlikely that a
> roundoff in the low order bit of a float should matter.
>
> But theres not really a good reason that we couldnt use doubles if needed .
>
> John
>
>
> On Mon, Apr 20, 2015 at 3:45 AM, Daniele Romagnoli <
> daniele.romagnoli@xxxxxxxxxxxxxxxx> wrote:
>
>> Hi List,
>> I'm using NetCDF Java 4.5.5.
>> I have noticed that when computing the LambertConformal projection
>> components (such as latin1, latin2...) in Grib1Gds I'm getting:
>>
>> latin1 = 25.00001
>> latin2 = 25.05002
>> dx1 = 13.545001
>> dy1 = 13.545001
>>
>> Instead of:
>> latin1 = 25
>> latin2 = 25.05
>> dx1 = 13.545
>> dy1 = 13.545
>>
>> Plus, I'm getting some additional precision loss when extracting these
>> attributes
>> from the associated grid_mapping variable, as numbers (double values).
>> I will surely investigate more on the topic to become more confident with
>> that code and I will read again about representation errors on floating
>> point arithmetics so my question could sounds trivial: Why these variables
>> and scale constants are floats instead of doubles? (is it for size and
>> performance issues?)
>>
>> Regards,
>> Daniele
>>
>>
>>
>>
>> ==
>> GeoServer Professional Services from the experts! Visit
>> http://goo.gl/NWWaa2 for more information.
>> ==
>>
>> Ing. Daniele Romagnoli
>> Senior Software Engineer
>>
>> GeoSolutions S.A.S.
>> Via Poggio alle Viti 1187
>> 55054 Massarosa (LU)
>> Italy
>> phone: +39 0584 962313
>> fax: +39 0584 1660272
>>
>> http://www.geo-solutions.it
>> http://twitter.com/geosolutions_it
>>
>> -------------------------------------------------------
>>
>> *AVVERTENZE AI SENSI DEL D.Lgs. 196/2003*
>>
>> Le informazioni contenute in questo messaggio di posta elettronica e/o
>> nel/i file/s allegato/i sono da considerarsi strettamente riservate. Il
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>> darcene notizia via e-mail e di procedere alla distruzione del messaggio
>> stesso, cancellandolo dal Vostro sistema. Conservare il messaggio stesso,
>> divulgarlo anche in parte, distribuirlo ad altri soggetti, copiarlo, od
>> utilizzarlo per finalità diverse, costituisce comportamento contrario ai
>> principi dettati dal D.Lgs. 196/2003.
>>
>>
>>
>> The information in this message and/or attachments, is intended solely
>> for the attention and use of the named addressee(s) and may be confidential
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>> Code).Any use not in accord with its purpose, any disclosure, reproduction,
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