Quoting Stuart Blair <stublair@anonymised.com>:
Dear Chris,
Thanks for getting back to me I can't express how much I appreciate
it! I;ve
had had a look at the links you sent and got a bit more confused i
think-
sorry!!
Hrm. This sort of begs a definitive newbie user introduction. Maybe
I'll start working on that.
Basically what i;m trying to do is to get a bunch of shape
files
showing the location of house crime throughout the ages in a
particular
place and make a site so people can track where crime has occurred
(possible
dissertation idea!)
Sounds cool. And I think we're actually at the point where we can
explain how to do this _relatively_ easily. We are working to make it
as easy as possible, and have made great strides, especially since more
and more tools are becoming available.
What i;ve basically done so far is to load the shapefiles onto
geoserver and
view them in udig and now i;m trying to put stuff up on the web so
have
managed to get myself a bit confused about what everything does now,
so as I
understand it; I could use postgis spatial database for example to
store all
my shapefiles and then load these into geoserver. this where i;m a
bit
confused about things and the main questions are:
In adding shapefiles to geoserver and creating a store for them, what
happens when defining a feature type for a particular shapefile, does
this
just define which features/data is returned by queriessent by jo
bloggs' sat
somewhere in cyberspace?
Yes. But GeoServer alone only makes it available according the OGC
protocols - wfs and wms. You can _get_ all the data, and jo blogg can
query them. But he has to know very specific queries. A decent
analogy is apache webserver. It serves up information on the web. And
jo blog can communicate with it directly in http, but that's not very
user friendly. So people make web browsers, which handle the
communication for them. Similarly there are a variety of clients for
WFS and WMS. UDig is an example of a desktop client. It translates
the protocols into a user interface that is easy to work with. But if
you want to display on the web then you need a web-based client. It
provides a user interface to the mapping protocols, but you interact
with it through a web browser, instead of on your desktop. See for
example http://mapbender.org. It translates a zoom icon into a new WMS
request with a smaller bounding box, ect. So GeoServer simply puts up
the ability to query features and maps. Any number of users can then
add that data to their maps, on desktop or web (intermap for example
lets you enter new web servers). But if _you_ want to make a useful
crime map, then you probably need to set up an individual web page for
it, that explains it, and picks the right layers. It can be your crime
data, and then you can use other servers to provide say road data and
satellite photos, to put your data in context.
I've only so far found a basic definition of a wms and a wfs - in
that all i
really know is that a wfs provides geographic features to the client
and
that it allows clients to change and add features to its
stores....whilst a
wms gives a picture of the data.. so i;m a bit confused as to what
each does
with regards to the user (i.e. joe bloggs) as geoserver is decribed
as being
a wfs with integrated wms and so i thought that geoserver would be
able to
display the shapefiles straight to the user - though i realise from
your
previous email this isn't correct.
Yeah, it can display shapefiles straight to the user, if he knows how to
enter strings like:
http://openplans.org/geoserver/wms?request=GetMap&length=340&width=440&bbox=-45,45,29,37&format=image/png&
ect.
But to be able to zoom in and out, and combine with other data, then you
need a client. There are very simple ones, like quickWMS. I mean, the
wms protocol is pretty easy. But it is a bit beyond a jo blog to look
at if you just set up a geoserver. Though in the future we would like
an integrated client - mapbuilder provides a number of pieces, but it
would be nice to combine with the GeoServer framework and know about
the layers that are set up on GeoServer.
expanding on the previous question - what exactly does mapbuilder do?
do
this just give geoserver the wms capabilities to display the
shapefiles? is
it a bit like a gui which can then be referenced by html without joe
bloggs
having to install some other data to view the image in his html
browser?
Yeah, that's pretty close. Mapbuilder is a library of widgets, that
make it a lot easier for jo blog to actually interact with the data.
does geoserver convert the shapefiles i feed into it into xml
format...and
if so when?
Yes, on the fly, whenever a user asks for them.
i guess what i;m a bit confused about (as there isn;t a clear
description/depiction on the net that i;ve found so far) is what
happens to
the shapefile from the moment it is passed into geoserver and has
been added
to the store, with it's feature-type confifguration defined, to how
the file
is then displayed to jo bloggs and how he can query it. what i would
really
appreciate (and i am so so sorry to bother you or anyone else for) is
a
quick decription of what data is stored where and what each bit of
the
process does ie. - postgis spatial database - provides store for
shapefiles.............
geoserver....................mapbuilder...............webpage as at
the
moment i'm kind of understanding mapbuilder to be a sort of gui which
you
reference in the html script.
Ok, so GeoServer can reference shapefiles directly, in which case
GeoServer reads it whenever a client makes a request, and displays it
appropriately. Optionally you can convert a shapefile to postgis, and
that's an alternative that geoserver can connect to. We recommend
doing so, since PostGIS is more robust, and you can just use the
shp2pgsql program included with postgis to perform it. So the data is
stored in either of those. GeoServer simply connects to them, it does
not convert them to an internal format or anything. So if you specify
a shapefile url, it is working against that shapefile. Whenever there
is a request, GeoServer transforms it into an image (WMS) or xml (WFS),
according to the parameters of the request (so it only does it to what
is asked for). Mapbuilder is a client, a nice user interface that
makes it easier for jo blog to make the requests that GeoServer
understands.
Again i am so sorry to bother you and really appreciate your time in
helping
No worries at all, we should explain it better. If you feel up to it,
you can make a page on the GeoServer wiki explaining what you've
learned to others. I can come in and clean it up, correct any errors,
but if you're asking the question there are definitely others who are
wondering too.
best regards,
Chris
me,
yours
stuart blair
----------------------------------------------------------------------------------------------------------------------------------------------------
On Apr 3, 2005 4:20 PM, Chris Holmes <cholmes@anonymised.com> wrote:
>
> Quoting Stuart Blair <stublair@anonymised.com>:
>
> > Dear Sir,
> >
> > Sorry to email you directly, though I have tried the
> > geoserver-devel@lists.sourceforge.net address, my emails seem to
be
> > returned
> > from that address!
> No worries, we've had problems with that before, I'm not sure why
> though. Perhaps it will work better if you join the list. But this
> should go to it fine, and I'm happy to relay your messages on.
Though
> I'm putting it to the users list, as it's a bit more appropriate
there.
>
> >
> > I have a very quick question, I;m interesting in building a web
GIS
> > system
> > and wanted to know what open source/free software would be
advisable.
> > I had
> > thought of running a postgis database, with geoserver, though am
> > quite new
> > to all this and so didn't know if anything else would be required
in
> > terms
> > of ensuring users using internet explorer or some other thin
client
> > would be
> > able to view the maps eventually put up on the web.
> Yeah, you'll need one more thing - a WMS/WFS client. The preferred
> GeoServer one is mapbuilder - http://mapbuilder.sourceforge.net.
It's
> a library of javascript widgets to use, so you have to figure a bit
> out, but it gives you a lot of control over how you want your page
to
> look. In 1.3 we have a mapbuilder demo, linked at the bottom of the
> welcome page (http://localhost:8080/geoserver). You also might
check
> out intermap - I think it's http://intermap.sourceforge.net. I
quite
> like it, it has a nice framework to add other maps, but it
basically
> needs to be spruced up with mapbuilder widgets. The other one I
like
> is http://mapbender.org. If you're php inclined it's the way to go
for
> sure.
>
> > Also, if my data is stored in GML format, can geoserver's wms
deliver
> > the
> > information or is it generally more adviseable to transform it
into a
> > different xml structure such as SVG via XSLT, as used by
> > http://www.isprs.org/istanbul2004/comm6/papers/697.pdf
> GeoServer can read GML - I'm not sure if we include that support by
> default, but the capability is in geotools, which means you can
plug it
> right into GeoServer. But I would recommend putting the data into
> postgis if at all possible. As for SVG, geoserver can not read SVG
-
> it doesn't quite have enough information to be a gis datasource.
> GeoServer has a bit of SVG output support, _from_ any of the other
data
> formats. But it does not currently support styling (though we may
> change to support styles, but having it be slow, using Batik -
> eventually we will get streaming with styles, but no one has the
> resources at the moment)
>
> >
> > I have found several sources on the internet though would
obviously
> > be very
> > grateful of any you could recommend to get me going. I was also
> > wondering
> > what the main differences between mapserver and geoserver are now
> > that
> > geoserver 1.3 has come online -with its' integrated wms features.
> Well, mapserver's wms is a lot more tested, and supports a lot more
> formats, and is probably faster. The advantages of GeoServer is
that
> it's a lot more user friendly, easier to set up and configure. And
it
> has better WFS support, including the ability to do transactions
(which
> means your users could update the map, if you wanted them to, or to
add
> stuff on top of it). MapServer has an integrated WFS, but it does
not
> support as many filters. So I'd say their comparable - it just
depends
> if you want to go with better tested, or more user friendly (and
help
> us test 
>
> >
> > Again I apologise you bothering you directly, though I would be
> > extremely
> > grateful if you or anyone else you feel might be able to answer
my
> > questions
> > could help.
> No worries at all, that's what we're here for.
>
> best regards,
>
> Chris
>
> >
> >
> > Yours sincerely,
> >
> >
> > Stuart Blair
> >
>
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