Hi all,

some time ago i had project where labeling was also pretty important
(parcels) so I came to one solution that perfectly suited my needs.

As I used OpenLayers for client, i had tiled and untiled layers at my
disposal. If you are only bound to tiled client, then using large
metatiling would be the best choice imho - as Chris allready said.

First, let me explain why i wasn't satisfied with existing choices:
1) metatiling with big tiling factor is usable only if you pre-seed
layers, as it could take longer time to generate this big image and
chop it to tiles (sometimes that can be really long process though,
and if your data tends to change frequently it just wont do) You will
still have 2/4 labels in small place at metatile intersection, which
can be annoying if you have parcel data.

2) fixed label position - if you have polygon data then position is
usually set somewhere close to the polygon center. this way many
labels don't show up if your map view covers only part of the polygon,
so you have to pan the map to the center of the polygon to see the
label. Kinda funny seeing big polygon that covers most of your map,
and the label doesn't show up :)

So I came up with an idea to create complex OL layer, that internally
creates two layers: first one tiled/cached geometry layer, and the
second one untiled layer for labels.
Each layer is configured with different settings, like different URLs
(to tilecache&GS), different style for label layer, image type and
resolutions.

Layer with labels had to be carefully prepared to keep the images
returned by server small (things like scale filtering on sld, custom
created pallete etc)

This way I had fast cached layers for geometries, and somehow less
faster layer for labels - but usually you dont notice its slow because
of the fast loading tiled layer beneath it :)

Hope it helps!

regards,
Ivan

On Fri, Mar 18, 2011 at 2:40 PM, Andrea Aime
<andrea.a...@geo-solutions.it> wrote:
> On Fri, Mar 18, 2011 at 2:07 PM, Chris Holmes <chol...@opengeo.org> wrote:
>>
>>
>> On Wed, Mar 16, 2011 at 11:17 AM, Andrea Aime <andrea.a...@geo-solutions.it>
>> wrote:
>>>
>>> On Wed, Mar 16, 2011 at 4:01 PM, Steve Way
>>> <steve....@infotech-enterprises.com> wrote:
>>> > Hi All,
>>> >
>>> >
>>> >
>>> > Just a curious question, but how do we avoid our labelling from looking
>>> > a
>>> > mess within openlayers or some other tiling client when trying to
>>> > configure
>>> > the overlaps etc which might be intersected by the edge of a tile?
>>>
>>> The short answer is, don't use tiling with labelling.
>>> The longer answer might be, reduce the mess using a tile cache and setting
>>> up meta tiling
>>>
>>
>> Note that you can use really large meta tiling.  I think ESRI's default is
>> 4096x4096, so 16x16 256 pixel tiles.  Though at that size it's much better
>> to pre-seed.
>
> Even at 16x16 meta tiling you'll get those unlucky polygons falling at 
> metatile
> system intersections labelled four times in a small space.
> It's just going to happen less
>
> Cheers
> Andrea
>
> --
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> GeoSolutions S.A.S.
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-- 
-------------------------------------------------------
Ivan Grcic
GeoSolutions S.A.S.
Software Engineer


Via Poggio alle Viti 1187
55054  Massarosa (LU)
Italy

phone: +39 0584 962313
fax:      +39 0584 962313
mob:   +39 328 0559267


http://www.geo-solutions.it
http://geo-solutions.blogspot.com/
http://twitter.com/geosolutions_it
http://www.youtube.com/user/GeoSolutionsIT


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