-------- Original Message --------
Subject: Re: Free, open source map publishing tool - gdal2tiles
Date: Tue, 20 Nov 2007 15:39:45 -0000
From: Nicholas Verge <[log in to unmask]>
To: Maps, Air Photo & Geospatial Systems Forum <[log in to unmask]>
On Tue, 20 Nov 2007 14:11:23 -0000, Maps-L <[log in to unmask]> wrote:
> -------- Original Message --------
> Subject: RE: Free, open source map publishing tool - gdal2tiles
> Date: Mon, 19 Nov 2007 15:22:34 -0800
> From: Matt Fox <[log in to unmask]>
> To: 'Maps, Air Photo & Geospatial Systems Forum'
> <[log in to unmask]>
>
>
>
> Nicholas, I think all Andrew was trying to say is KML has its place and
> is
> evolving more and more every year .
Granted it has its use, but in terms of a format for public institutions
to provide data, it is not the most useful or optimal. KML is foremost a
publishing format.
Re "...into into a more sophisticated GIS tool". I feel i must comment on
this often made statement.
Hmmm. Does Google Earth provide for sophisticated querying of data,
processing and reformatting of the data? No. This is fundamental to the
operation of a GIS.
Google Earth is in no way a GIS, it is not now and very probably never
will be. For one thing working with geographic information, commonly
requires substantial computational horsepower for the job to be done in
resonably acceptable time. Even though GE emplys a supercomputer, the data
transfer rates on the fastest internet connnections are orders of
magnitude slower than the slowest links bewtween components within a PC.
As a result it is unlikley that in the foreseeable future that internet
bandwidth will become sufficiently high to allow efficient GIS data
processing on an extenal system. More likley, is that PCs will become so
powerful that technology similar to GE will be able to run locally,
provided via GISs and even prosumer applications. GE will be a thing of
the past in a few years.
So what is GE?
GE is primarily about providing a means to allow public viewing of
proprietry data as a lure for the public to look at advertising. Sure the
public is allowed to add their own content over the top in a limited and
controlled way (read the GE T&Cs). However, overall GE is of very little
use and would go as far as to suggest thats its creation is one of most
detrimental developments that has occurred within the GI industry, since
if gives many GI novices the false idea that it is what geographic
information analysis is about, when it is no such thing. Using GE is
rather like going to a museum and looking at the exhibits there. You can
look, you can draw them, and you might in a limited way be able to
interact with them. But you cannot take them home, modify them, analyse
them in complex ways, cut bits off them, change their colour combine them
with other items, to create something enirely new. This is what a modern
full-featured GIS allows with your own GI.
>
> Every data format has advantages/disadvantages. KML's primary advantage
> is
> making data available over the internet to a large non-technical audience
> (such as library patrons). 5-10 years ago almost all GIS data required
> the
> user to spend $1,000's on a complex GIS package. KML opens all of that
> data
> up to anyone with a web browser and/or viewer such as Google Earth.
I say it is far better and more rewarding for the those who wish to use GI
to use a GIS, be it a free, an inexpensive or a platinuma-plated one. They
dont need to use GE for many of the things they wish to do. Moreover they
can then have full control over what they do and how they do it.
>
> No one is saying KML should replace SHP, GeoTIFF, JPG/JGW, etc. format
> for
> archival or more complex GIS purposes. But there is a reason most/all of
> the major GIS platforms now support KML at some level.
But this is what is happening.
To return to the original objection, public libraries should be providing
scans of maps etc in standard open image file formats (tiff/geotiff, .JPG,
JP2, ECW) which people can already use and view, without the need for
loading them onto GE and in doing encouraging use for a privately owned
facility.
>
> Also, there are very few data formats that have the projection and
> position
> information invisibly embedded in the file itself. SHP files don't even
> do
> that.
Yes agreed. This is well known and it is why i did not cite shape files as
an example. But shape files can use any geographic coordinate system.
There is just no way of storing information about which is used in them.
This information has to be provided in a metadata file. Manifold System
for example exports a .xml file with this information whenever it exports
GI (images or drawings).
--
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Nicholas J. Verge BSc. FGS
Henley-on-Thames, Oxfordshire, UK
Geologist
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