[GRASS-user] Copy an existing location

[Rainer M Krug]

"Bartolomei.Chris" <Bartolomei.Chris at ensco.com> writes:

> Hi Rainer,
> I had stated that I wasn't 100% sure and just to look into it - I had
> recalled reading about lossy and lossless data some time ago.
> For a quick look into it, Wikipedia has a decent article
> (https://en.wikipedia.org/wiki/Lossless_compression and
> https://en.wikipedia.org/wiki/Lossy_compression) ... as I briefly
> looked through it just now, it appears gz and zip use a lossless
> algorithm so they should be fine to use. Tar (if I remember right)
> concatenates files into an archive and is not a compression tool.
> It looks like lossy algorithms are used more for music and video and some images according to the articles.
> I was just putting up a yellow flag as a caution to look into it as I
> wasn't sure and I wouldn't want to give someone bad advice.

OK - so we can clarify:

*File Compression* is per definition lossless (zip, gz, 7z, bz,
 ...). Otherwise you would not be able to restore ftom archives.

Compression of *content of the file* can be lossy (mp3, jpeg, ...).

Cheers,

Rainer

>
> Chris Bartolomei P.E.
> Engineer/Scientist
> ENSCO, Inc.
> bartolomei.chris at ensco.com
> ________________________________________
> From: Rainer M Krug [Rainer at krugs.de]
> Sent: Friday, April 29, 2016 12:35 AM
> To: Bartolomei.Chris
> Cc: Janet Choate; grass list
> Subject: Re: Copy an existing location
>
> "Bartolomei.Chris" <Bartolomei.Chris at ensco.com> writes:
>
> [snip (4 lines)]
>
>> The reason I say this is the file
>> compression I suggested may cause some data loss ... look into
>> lossless data compression algorithms and you'll see what I'm talking
>> about.
>
> Could you please elaborate and give some references where lossless data
> compression (gz, zip) may cause data loss? Especially tar.gz is used for
> ages in archival and backup?
>
> Rainer
>
>
> [snip (46 lines)]
> --
> Rainer M. Krug
> email: Rainer<at>krugs<dot>de
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-- 
Rainer M. Krug
email: Rainer<at>krugs<dot>de
PGP: 0x0F52F982
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