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| Subject: | RE: GISList: Working with large rasters ~100Gb and GIS |
| Date: |
03/17/2003 10:17:19 AM |
| From: |
Karen Morley |
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That statement was almost true before the last release of MrSID compression
technology. Now MrSID has truly lossless compression at rations of 2:1-
about 8:1 with numeric radiometric and geometric fidelity. It also has
native support in nearly every major GIS package obviating the need for
viewers or plugins. I won't do a commercial as that is not what this list
is for but did want to clear that up. For more info go to
www.lizardtech.com
-----Original Message-----
From: Voets, D. [mailto:D.Voets@esrinl.com]
Sent: Friday, March 07, 2003 7:36 AM
To: 'gislist@geocomm.com'
Subject: RE: GISList: Working with large rasters ~100Gb and GIS
Dear Christoforo,
That is very true. ECW files can give you a compression ratio 16:1 as you
noted, without visible loss. Free of charge viewing tools are available.
MrSID can give you comparable results. The compression ratios are comparable
to ECW, they also have free viewers for many applications. You can also
serve the information through webservers. It's all very comparable,
technologically speaking. Integration in applications and the cost of
conversion and implementation might make a difference between ECW and MrSID,
but technologically speaking the differences aren't large.
All the best,
Dirk Voets
Support Engineer
ESRI Nederland B.V.
Tel : 010 - 217 07 50
Email : GISsupport@esrinl.com
Internet : http://www.esrinl.com
Call aanmelden via Internet: http://www.esrinl.com/ondersteuning/callNL.asp,
FAQ's op: http://www.esrinl.com/ondersteuning/vragen.asp
-----Original Message-----
From: Cristoforo Abbattista [mailto:crisabba@planetek.it]
Sent: Friday, March 07, 2003 4:24 PM
To: 'gislist@geocomm.com'
Subject: RE: GISList: Working with large rasters ~100Gb and GIS
Hi list
what I can say you is that in our developments we manage such files
through Image Web Server (by Earth Resource Mapping) and I had
never found
Internet applications which manage these huge files in other ways
For example in the site
http://www.cartografia.regione.lombardia.it/cartanet
we deliver to web clients an orthophoto whose not compressed size is
200GB, while compressed in ECW format is 12GB
I think that you should know that there are many free plug-in
(http://www.ermapper.com/download_new/download.aspx#1
or
http://www.planetek.it/prodotti_eng.asp)
to manage ecw files in your typical applications like Photoshop, MS
Word
or other Regards
Ing. Cristoforo ABBATTISTA - WebGIS Project Manager
Planetek Italia s.r.l.
Via Massaua, 12 I-70123 Bari
Tel.: +39 080 5343750 - Fax: +39 080 5340280
cristoforo.abbattista@planetek.it
Web: http://www.planetek.it
> Dear Uffe and others,
>
> It greatly depends on the type of data you are loading. ArcSDE
> supports a number of compression techniques, and these compression
> techniques may greatly reduce the amount of data stored. However, the
> compression techniques can be relatively to very ineffective compared
> to uncompressed data, depending on the type of data. Scanned maps and
> vector data generated images can greatly benefit from a compression
> type like LZ77. Areal photographs etc very often increase in size
> using LZ77, compared to uncompressed. ArcSDE also supports a JPEG
> lossy compression scheme, and that will compress areal photographs
> quite well. The drwback of that approach is that JPEG is lossy, and it
> is much more lossy than MrSID and ECW are.
>
> So, there are a number of factors that greatly influence the resulting
> size in the database. these factors are: - the compression in the
> original file. TIFF input files can be uncompressed, but they can also
> be stored as Packbits compressed, LZW compressed, Fax Group 3 and 4
> compressed, even JPEG compression can be used within a TIFF file. -
> The type of data in the original files. vector generated images and
> scanned maps are always easier to compress than areal photographs are,
> if you want to keep the quality comparable to the original data. - the
> compression scheme you choose in the database. - the type of database.
> Though I'm not sure about this, I get the impression that Oracle tends
> to be a bit more compact than for instance SQLserver. However, I may
> be mistaken there.
>
> The discussion is indeed very interesting. Storing and providing to an
> organization 100GB of areal photographs is quite uncommon (yet), there
> is no silver bullet that will do the overall trick. I am curious to
> know the outcome.
>
> All the best,
>
> Dirk Voets
> Support Engineer
> ESRI Nederland B.V.
> Tel : 010 - 217 07 50
> Email : GISsupport@esrinl.com
> Internet : http://www.esrinl.com
>
> Call aanmelden via Internet:
> http://www.esrinl.com/ondersteuning/callNL.asp, FAQ's op:
> http://www.esrinl.com/ondersteuning/vragen.asp
>
>
> -----Original Message-----
> Fro
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