-------- Original Message --------
Subject: Re: formats of map compression
Date: Fri, 23 May 2008 08:40:28 -0700
From: Brian Bach <[log in to unmask]>
To: [log in to unmask]
Nicholas and all,
Thanks for the warnings regarding the Byzantine conditions surrounding
Mr Sid use. I have praised their technology and quality in the past, but
the roadblocks they throw up in the name of profit are ominous.
I mention this because our library, (as well as the two-state
consortium of which we are a partner) is experiencing an outrageous
price-hike from the company that currently provides our catalog
architecture. They are firm in their offer, so, our whole consortium is
switching to OCLC. It's a considerable hassle, but in the long run we no
longer have to be so vulnerable to the whims of the corporate mentality.
By their rigidity, the company we use now loses a significant contract.
How's that for good business practices?
We in public sector libraries have to be very wary of these and other
tactics, some of which border on extortion.
Brian
Brian P. Bach
Documents/Maps
Brooks Library
Central Washington University
400 E. University Way
Ellensburg, WA 98926-7548
USA
[log in to unmask]
http://www.amazon.com/Calcuttas-Edifice-Buildings-Great-City/dp/8129104156
>>> Angie Cope <[log in to unmask]> 5/22/2008 1:55 PM >>>
-------- Original Message --------
Subject: Re: formats of map compression
Date: Thu, 22 May 2008 21:47:21 +0100
From: Nicholas Verge <[log in to unmask]>
To: [log in to unmask]
Dear Linda,
You asked:
"What kind of formats have You used creating datafiles – MrSid or
JPEG2000, or someone [something] else?"
As a national librarian, i expect you are aiming to make your data
easily
accessable and usable by as many people as possible. Therefore,
whatever
format you use, please do not use MrSID or any other proprietry format
for
which there no efficient decompression algortithms publicly released
and
freely available. Contrary to what has been stated MrSID is not an
industry standard format, although Lizardtech has tried every
commercial
and legal trick in order to present it as such in order to entrap the
unwary into using its expensive software to compress to and decompress
images from MrSID.
Why you should not provide images in MrSID format:
MrSID files can be viewed when in native compressed form by various
applications. However, major problems arise when the images need to be
used in a GIS environment or similar. Then, it may be necessary to
decompress the MrSID image to a conventional image file format. This
is
usually done so that the image can be cropped to an area of interest,
its
contrast and colour adjusted or so that the projection of the image (if
a
geographical one) can be changed. All these can only be done to an
image
if it not encoded using wavelet-baed algorithms or if it is in such a
file
format, only once the image has been decompressed.
To decompress MrSID images efficiently requires use of properietry
technology owned by Lizardtech, for use of which this company demands
high
licensing fees. There are freeware decompression tools that can also
be
used for this, but Lizardtech has not released software development
kits
to allows third parties to produce efficient MrSID decompressors. As a
result the freeware decompressors are hobbled and are very slow.
Decompression of even relatively small files can take many hours.
Large
files can take days.
Fortunately, you may achieve the same image compression, by using
JPEG200
or its predecessor ECW. Both of these formats ARE widely used in the
GIS
and remote sensing industry and the developer of JPEG2000, ER Mapping
(now
part of Leica) has released SDKs to third party software devlopers so
that
JPEG2000 files can be used and decompressed easily. They also released
freeware to allow the same. Therefore, on behalf of the GIS and remote
sensing community, if you wish to provide map scans and supply these in
a
format that uses wavelet-based compression technology, please only use
JPEG200 or ECW.
Also, regardless of the public domain technology i hope you will use,
it
is equally important that you scan the maps at sufficient high
resolutio
that the information shown on the map is legible and is not obscured
by
file compression. This is particulallry essential for small labels and
closely spaced topographic contours. To ensure that these remain
legible
please scan at 400dpi or greater, and in 24-bit colour.
Sincerely,
Nicholas Verge
On Wed, 21 May 2008 18:25:37 +0100, Maps-L Moderator <[log in to unmask]>
wrote:
> -------- Original Message --------
> Subject: formats of map compression
> Date: Wed, 21 May 2008 19:41:59 +0300
> From: Linda Akmentiņa <[log in to unmask]>
> To: <[log in to unmask]>
>
>
>
> Dear Colleagues!
>
>
> The matter of my inquest is formats of map compression.
>
>
> The Department of Cartographic Materials of National Library of
Latvia
> have started a Digital Map Project. What kind of formats have You
used
> creating datafiles – MrSid or JPEG2000, or someone else?
>
>
> What are Your thoughts regarding this matter?
>
> Thank You for sharing Your experience,
>
>
>
> map librarian,
>
> Linda Akmentina.
>
--
----------------------------------------------------------------------
Nicholas J. Verge BSc. FGS
Geologist and geological remote sensing/GIS consultant
CEO,
Earthscience Technologies,
Henley-on-Thames, Oxfordshire, UK.
Voice: ++ 44 (0)1491 572022 (office hours 0900-2200UTC, Monday -
Saturday)
Email: [log in to unmask]
|
