[ka-Map-users] ka-Map and OpenLayers

Steve Lime Steve.Lime at dnr.state.mn.us
Wed Jun 21 15:47:35 EDT 2006 

I was thinking along the lines of MapServer being able to generate a pile of tiles
but would turn over cache management (e.g. creating an image only once) to 
something really good at that sort of thing, like Squid. Extending the concept
of rendering tiles using metatiles seems to fit within the "render high quality
maps" area.

Steve

>>> Daniel Morissette <dmorissette at mapgears.com> 6/21/2006 7:04:15 AM >>>
Steve Lime wrote:
> 
> One thought might be to look at tile-caching as a part of MapServer proper.
> Other projects (GeoServer, MapGuide, etc...) could follow suit... That could
> provide a clean break between client and server.
> 

I think I'd rather see tile caching as a layer on top of MapServer and 
possibly other servers instead of embedding it in MapServer, and let 
MapServer concentrate on what it's best at: render high quality maps.

A simple way to achieve that would be to modify ka-Map's tile.php to 
issue WMS GetMap requests instead of calling MapScript's $map->draw() 
when rendering metatiles. This would allow plug and play integration 
with any WMS server.

Down the road I think tile caching needs to become more advanced than 
just the current tile.php and might need to become a beast in itself 
that comes with its own http server (or as a fcgi or Apache module), at 
that point, tight integration inside MapServer would probably make even 
less sense.

Just my 0.02$

Daniel
> Steve
> 
> 
>>>>Paul Spencer <pspencer at dmsolutions.ca> 6/20/2006 4:18:23 PM >>>
> 
> Good point ... we were discussing tiling today.  I can actually see  
> ka-Map turning into a tile-cache server project separate from  
> OpenLayers.  The shortest path to integration is to add a kaMap layer  
> and tile class to OpenLayers and use the existing kaMap tile.php to  
> serve tiles to it.  I'm currently working on designing a better  
> strategy for tile caching since the current directory structure is  
> very limited for large caches (it only goes one directory deep when  
> you really look at it).
> 
> One of my personal goals would be to see a standards-based tile  
> service come into existence.  There has been some discussion on this  
> on the webmap-discuss at mail.osgeo.org list and in the following wiki  
> page:
> 
> 
>>http://wiki.osgeo.org/index.php/WMS_Tile_Caching 
> 
> 
> I'm not sure I like the direction it is currently going, but I like  
> the overall concept.
> 
> Cheers
> 
> Paul
> 
> 
> On 20-Jun-06, at 5:00 PM, Steve Lime wrote:
> 
> 
>>What would be the plans on the server-side? OpenLayers doesn't seem to
>>cover that aspect.
>>
>>That said, personally I trust your judgement w/regards to ka-map  
>>and will
>>end up using whatever comes out of this union. The sooner a stable API
>>is in place the better since fear of shifting sands may keep folks  
>>away or
>>from going into production.
>>
>>Steve
>>
>>
>>>>>Paul Spencer <pspencer at dmsolutions.ca> 6/20/2006 2:56:05 PM >>>
>>
>> From my initial review of the code base and project objectives, I
>>feel that it offers a cleaner code base and architecture.  It is more-
>>or-less what I would do with the ka-Map code base if I wrote it.
>>
>>The differences are more in the project objectives.  One of these is
>>to be able to integrate Google, VirtualEarth, Yahoo and other
>>commercial/free tiles without violating their terms of use.  The end
>>result is that the application adapts to the limitations of an
>>existing set of tiles (tile sizes, projection etc).  It is then
>>possible to build overlays that morph based on the underlying layer
>>source.  I'm not sure this is a big priority for me, but it does make
>>the API itself more compelling I think.
>>
>>I'm not sure that I have described this very well.  Perhaps John
>>could explain this concept better (since he was the one who explained
>>it to me :))
>>
>>John and I agreed that the projects should merge.  He/OpenLayers are
>>willing to start from ka-Map and integrate the OpenLayers stuff if
>>necessary.  I just feel that it would be easier to move the ka-Map
>>code into OpenLayers rather than the other way around.
>>
>>One big disadavantage to the ka-Map community is that the API will
>>change.  We may be able to provide a compatibility API but I think
>>that would be more work than it would to help people convert their  
>>apps.
>>
>>Perhaps a reasonable compromise would be to develop a Google API
>>clone (something I have been against previously), which could make
>>OpenLayers a compelling environment for existing Google-hackers plus
>>give them the option to move from Google in the future if the terms
>>of use/ads become cumbersome?
>>
>>Cheers
>>
>>Paul
>>
>>
>>On 20-Jun-06, at 3:15 PM, Steve Lime wrote:
>>
>>
>>>What does OpenLayers offer that ka-map doesn't ( besides a better
>>>name ;-) )? The
>>>list you reel off of limitations is pretty substantial.
>>>
>>>Steve
>>>
>>>
>>>>>>Paul Spencer <pspencer at dmsolutions.ca> 6/20/2006 1:28:19 PM >>>
>>>
>>>Hello ka-Mappers!
>>>
>>>I had a very interesting discussion with the developers of
>>>OpenLayers, a javascript api for tiled maps.  Turns out OpenLayers
>>>and ka-Map are very similar.  We decided that it would be beneficial
>>>for both communities if we attempted to merge the projects.  The
>>>purpose of this email is to present this idea to the ka-Map community
>>>in order to generate some discussion on the subject.
>>>
>>>OpenLayers is hosted at http://www.openlayers.org/.  They have some
>>>very interesting objectives which I think are compatible with ka-
>>>Map.  Take a look at their site.
>>>
>>>OpenLayers is written on top of prototype.js, which was one of the
>>>things I was planning to do with ka-Map in the next couple of weeks.
>>>It has a very nice looking architecture and the code base is very
>>>readable.
>>>
>>>It is lacking quite a few things that ka-Map has:
>>>
>>>* core tiling engine is very similar, but it is not quite as optimal
>>>(doesn't reuse images for instance)
>>>
>>>* overlay stuff is point/text only
>>>
>>>* lacking tools (layer controls, scale bar etc) and the windowing
>>>stuff
>>>
>>>* lacking query capability
>>>
>>>* tile caching
>>>
>>>* probably several other things I can't think of right now
>>>
>>>I think that there are some differences in how OpenLayers and ka-Map
>>>approach things, but I'm not entirely sure that they are significant.
>>>
>>>At this point, I am proposing to join the two projects into a single
>>>project.  My desired approach would be to start with the OpenLayers
>>>code and start to bring over the parts of ka-Map that I(we) feel are
>>>missing.
>>>
>>>Please let me know what you think of this.  And point out all the
>>>problems you can think of.
>>>
>>>Cheers
>>>
>>>Paul
>>>
>>>+-----------------------------------------------------------------+
>>>|Paul Spencer                           pspencer at dmsolutions.ca   |
>>>+-----------------------------------------------------------------+
>>>|Applications & Software Development                              |
>>>|DM Solutions Group Inc                 http://www.dmsolutions.ca/| 
>>>+-----------------------------------------------------------------+
>>>
>>>
>>>
>>>
>>>_______________________________________________
>>>ka-Map-users mailing list
>>>ka-Map-users at lists.maptools.org 
>>>http://lists.maptools.org/mailman/listinfo/ka-map-users 
>>>
>>
>>+-----------------------------------------------------------------+
>>|Paul Spencer                           pspencer at dmsolutions.ca   |
>>+-----------------------------------------------------------------+
>>|Applications & Software Development                              |
>>|DM Solutions Group Inc                 http://www.dmsolutions.ca/| 
>>+-----------------------------------------------------------------+
>>
>>
>>
>>
> 
> 
> +-----------------------------------------------------------------+
> |Paul Spencer                           pspencer at dmsolutions.ca   |
> +-----------------------------------------------------------------+
> |Applications & Software Development                              |
> |DM Solutions Group Inc                 http://www.dmsolutions.ca/| 
> +-----------------------------------------------------------------+
> 
> 
> 
> 
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-- 
Daniel Morissette
http://www.mapgears.com/ 
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