[mapserver-dev] RFC: GMaps API for mapserv

[Steve Lime]

I've been using the pre-clip labeling with tilecache (works nifty), but still with metatiles. Has anyone
tried tilecache without metatiles but using the options Paul mentions. In theory that should really help
although there are likely still issues with things like highway shields and such since it's hard to label a
highway that runs for 500 miles before clipping.

We may have to take a look at interval-based labeling options for linear features. For example, we might
label a highway every 20 miles and those positions could be based on an initial offset from a node (so you
don't start labeling right at the beginning)  and would be stable across tiles.

I agree with Paul's ideas to force things, and the parameter name changes (mode=tile&tile=...).

Steve

>>> On 4/10/2008 at 4:10 PM, in message
<EC0C0D10-AE28-4C4C-AEC7-56396445C95C at dmsolutions.ca>, Paul Spencer
<pspencer at dmsolutions.ca> wrote:

> On 10-Apr-08, at 5:33 PM, Stephen Woodbridge wrote:
>> Paul Ramsey wrote:
>>> On Thu, Apr 10, 2008 at 1:07 PM, Stephen Woodbridge
>>> <woodbri at swoodbridge.com> wrote:
>>>> It seems that the meta-tiling and labeling issues will need to be  
>>>> addressed
>>>> eventually, so I think some discussion of how they would be done  
>>>> from a
>>>> design point of view should be undertaken. If these can not be  
>>>> easily solved
>>>> in this architecture then that might indicate a problem.
>>> Metatiling implies caching, since you'll necessarily be producing way
>>> more tiles for each request than you need, you should store the  
>>> spares
>>> for the future. And I don't think we want to go there. At least, some
>>> folks don't want to go there.
>>
>> Yes, I agree with the fact the metatiling is out of scope. I think  
>> the point that I did not make so clear is that assuming someone  
>> wants to do metatiling, say using some script or tilecache or  
>> whatever. Is there anything in the implementation or design that  
>> would prevent one from generating metatiles and chopping them up via  
>> a script and storing them somewhere outside of mapserver? If yes, is  
>> removing that within the scope of things or not?
> 
> I think that you should do a couple of things differently in mode=gmap:
> 
> * Steve Lime just added a processing option to enable mapserver to  
> calculate label positions before features are clipped.  With PARTIALS  
> TRUE, this should eliminate the label problems to a large extent when  
> producing tiles since adjacent tiles should put the label in the same  
> place (relatively speaking) and labels should end up continuing nicely  
> across tile boundaries.  So this processing option and PARTIALS TRUE  
> could be forced on in this specific mode
> 
> * draw map tiles a bit bigger and trim the result to reduce edge  
> effects.
> 
> If you did this, with an apache module, meta tiles would be a thing of  
> the past - well maybe not, but it would go a long way to avoiding the  
> need for them.
> 
> Also, I think you should call it mode=tile :)
> 
> And ... +1!
> 
> Cheers
> 
> Paul
> __________________________________________
> 
>     Paul Spencer
>     Chief Technology Officer
>     DM Solutions Group Inc
>     http://www.dmsolutions.ca/ 
> 
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