On Wed, Jul 1, 2015 at 9:25 AM Andrea Aime <[email protected]>
wrote:
> On Tue, Jun 30, 2015 at 11:21 PM, Gabriel Roldan <[email protected]
> > wrote:
>
>> Thought it did exist but it looks like it doesn't, so it might make for a
>> nice weekend project.
>>
>> I know what the gt-grid module does but never used it. Yet it'd be quite
>> handy to be able of configuring a read only grid layer in geoserver that
>> doesn't take any space on disk but is computed on the fly using gt-grid?
>> quite the same that's done by the mini-wms embedded in the geoserver SRS
>> List demo, but for general use (see where the map showing the area of
>> validity for each CRS has a grid on it? [1]).
>>
>> But before giving it a shot:
>> - really it doesn't exist?
>> - would it be useful for others at all?
>> - if so, feature requests?
>>
>
> Hi Gabriel,
> there is much to say on the topic, in summary, it's not as easy as it
> looks (doing the store it's indeed easy, using it for grids not as easy as
> it seems).
>
> First, Ian has been looking into the subject recently, you might want to
> synch up with him:
>
> http://blog.ianturton.com/geotools/mapping/cartography/2015/06/17/fun-with-graticules.html
> There is also a relevant thread on the geotools developer mailing list,
> interesting stuff there too.
>
> About the usage issues, there are a few:
>
> - Reprojection, right now the store generate lines made of two points,
> and our reprojection engine still reprojects point by point, without on the
> fly densification when a line is too long to be reprojected "as is". It's a
> feature that I have in my backlog, but not sure if and when it's going to
> be implemented. I think the grid module can densify, but to get good
> results one would have to densify dynamically, depending on the zoom level
> and target projection... which is a bit of trouble when you just give a
> layer for anybody to use against the 5000 projections we expose
> - Labelling, often people want the ordinate of the grid line shown at
> the map margins, which is something we cannot easily do right now, although
> it might be doable with a rendering transformation (intersect with the
> rendering bbox, pad back from the border enough, add an attribute to give
> the label vertical or horizontal orientation)
> - Multilevel grids: often the maps require grids that are multilevel,
> every 10 degrees depicted one way, and the others every one in a different
> way
>
> Now, I believe that all of the above issues can be solved via SLD and
> rendering engine improvement with some extra effort, but they are not
> exactly trivial. I guess that's why people have considered doing them as
> decorations instead, and/or as DirectLayer.
>
>
The code I developed handles densification, and multilevel grids are the
next issue I plan on looking at and then I wanted to work out how to move
the labels to the edges of the screen (I hadn't thought of transforms but
that makes sense).
Then I planned to stuff everything into a direct layer and hope for the
best (or ask Jody for help).
> All in all, I'd be favorable with just creating a grid store too, that's
> something I'd been quite tempted to do myself, we should just explain to
> the user base what the current limitations are
>
>
A store could work and would allow the user to specify the CRS and bounds/
levels that they wanted.
Any way I'm definitely interested in this so keep me in the loop please
cheers
Ian
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