[webmap-discuss] OGC and google style tiling
Steven M. Ottens
steven.ottens at geodan.nl
Thu Apr 27 04:32:40 EDT 2006
Hi Paul,
Why did you choose to use a php script to handle tiling? It makes it
much harder for ka-map to become a general webmapping client, currently
it is strongly tied to mapserver. Also for me it's more difficult to
integrate it with mapbuilder, if I want to keep mapbuilder general.
Why not integrate the routine in the clientside and request tiles like this:
http://www.edugis.nl/cgi-bin/edugis/mapserv.cgi?map=maps/edugis/base.map&VERSION=1.1.0&REQUEST=GetMap&LAYERS=topografie&STYLES=default&SRS=EPSG:4326&BBOX=4.833984375,52.26815737376817,4.921875,52.32191088594773&WIDTH=256&HEIGHT=256&FORMAT=image/png&TRANSPARENT=TRUE&EXCEPTIONS=INIMAGE
(this is a request from a gmap-based application)
The important part, obviously, to make sure that the tiles have the same
size (easy) and the same coordinates regardless of the client.
grt,
Steven
Paul Spencer wrote:
> Ok. I'm not sure if the URLs to the tiles are standard. The URL goes
> to a tile.php script which converts special pixel coordinates into
> geographic coordinates. The math for the conversion is very simple
> though, all you need to know is the size of a pixel in geographic
> coordinates.
>
> I'll need to look into mapbuilders controls to understand how to do
> the integration. Perhaps this could be the start of a common API? ;)
>
> Cheers
>
> Paul
>
> On 13-Apr-06, at 11:33 PM, Cameron Shorter wrote:
>
>> The "standard URL" I was refering to is the URL of a tile.
>>
>> Both ka-map and mapbuilder have both implemented much of the same
>> functionality. We will need to work out a logical place to split
>> between the ka-map code and the mapbuilder code.
>>
>> I think it would be difficult to use Mapbuilder without Mapbuilder
>> controls. Probably what we would need to do is convert your ka-map
>> tools to fit within the Mapbuilder framework.
>>
>> Paul Spencer wrote:
>>> Cameron,
>>> what do you mean by standard url? ka-Map has a javascript API that
>>> handles all the navigation including the smooth panning of the
>>> map. While not exactly like google, the api is roughly equivalent.
>>> Not sure if you could use mapbuilder's controls or not, it would be
>>> cool if you could.
>>> I'll take a stab at installing/running MapBuilder this weekend. Do
>>> I need to do anything special to use the Google Map layer?
>>> Cheers
>>> Paul
>>> On 13-Apr-06, at 6:26 AM, Cameron Shorter wrote:
>>>> Paul,
>>>> I'm currently allowing a Google Map layer to be included as one of
>>>> the layers rendered by Mapbuilder.
>>>>
>>>> So if you have a standard URL used to call a tiled map server,
>>>> then we can create a Mapbuilder Layer which accesses the URL
>>>> (we'd probably base our code on your existing ka-maps code).
>>>>
>>>> I'd expect that we would use the Mapbuilder pan/zoom type tools
>>>> and buttons rather than the ka-map tools.
>>>>
>>>> Is that what you were thinking about?
>>>>
>>>> Paul Spencer wrote:
>>>>
>>>>> What would be really nice would be to have a MapBuilder widget
>>>>> for ka- Map ;) Mike Adair has mentioned that this is both
>>>>> possible and quite easy to do. Not being very familiar with
>>>>> MapBuilder, I can't comment on that. But if it were possible to
>>>>> do, ka-Map would provide you a tiled interface and you could use
>>>>> your existing map file to do it without breaking ogc compatibility.
>>>>> Cheers
>>>>> Paul
>>>>> On 12-Apr-06, at 4:33 AM, Steven M. Ottens wrote:
>>>>>
>>>>>> Hi Bart,
>>>>>>
>>>>>> Thanks for the mailinglist tip.
>>>>>> It might be possible to rasterize our vector data, but we've got
>>>>>> quite
>>>>>> some datasets and there will be more of them. It also makes us less
>>>>>> flexible. Obviously we've to make a trade-off on flexibility
>>>>>> and speed.
>>>>>> We hope that with cached tiles we can have both the flexibility and
>>>>>> speed. If we rasterise it would make sense to rasterise into
>>>>>> fixed tiles
>>>>>> I guess.
>>>>>>
>>>>>> Steven
>>>>>>
>>>>>> Bart van den Eijnden wrote:
>>>>>>
>>>>>>> Hi Steven,
>>>>>>>
>>>>>>> there is an OGC list to discuss tiling:
>>>>>>>
>>>>>>> http://lists.eogeo.org/mailman/listinfo/tiling
>>>>>>>
>>>>>>> check the archives there.
>>>>>>>
>>>>>>> What you could also do, since I assume your data is pretty
>>>>>>> much static, is
>>>>>>> use UMN Mapserver to rasterize all your vector data (create
>>>>>>> Geotiffs e.g.)
>>>>>>> and serve out the rasters instead. I guess the classifications
>>>>>>> used are
>>>>>>> heavy on CPU usage, and pre-classified rasters would solve
>>>>>>> that part at
>>>>>>> least.
>>>>>>>
>>>>>>> Best regards,
>>>>>>> Bart
>>>>>>>
>>>>>>>
>>>>>>>> Hi all,
>>>>>>>>
>>>>>>>> For those who don't know: I'm one of the lead developers on
>>>>>>>> the EduGIS
>>>>>>>> project, a site which aims to introduce highschool students
>>>>>>>> to GIS. The
>>>>>>>> site contains a webmapping part, which combined with so called
>>>>>>>> 'lesson-modules' can be used inside the classroom.
>>>>>>>> We aim to be able to have at least 200 students access the
>>>>>>>> site at one
>>>>>>>> time. Since it's being used inside the classroom it means that
>>>>>>>> a lot of
>>>>>>>> students will do more or less the same thing at the same time
>>>>>>>> (following
>>>>>>>> the tasks in the lesson-modules). This causes quite some
>>>>>>>> stress on the
>>>>>>>> server. Since it's a free site we have limited budget and
>>>>>>>> cannot put a
>>>>>>>> google-style server park behind it ;(
>>>>>>>>
>>>>>>>> Right now we've got apache to serverside cache the umn
>>>>>>>> mapserver output.
>>>>>>>> This obviously works only for those images that are requested
>>>>>>>> twice
>>>>>>>> (like the first mapimage). Right now about 30 students can
>>>>>>>> work at the
>>>>>>>> same time without it becoming unworkable slow. Since
>>>>>>>> serverside caching
>>>>>>>> works, the next logical step to boost performance would be
>>>>>>>> using tiles
>>>>>>>> like google.
>>>>>>>> But..
>>>>>>>> From what I know, tiling breaks OGC compatibility, right?
>>>>>>>> We're using Mapbuilder as client and we prefer to keep using
>>>>>>>> it, since
>>>>>>>> it's turning into a rather featureful client on the EduGIS
>>>>>>>> site. But the
>>>>>>>> question arises how to implement tiling inside
>>>>>>>> WMC/OWS-context without
>>>>>>>> breaking OGC too much.
>>>>>>>> Also I'm interested in the used algorithms to get tiling working.
>>>>>>>>
>>>>>>>> Cheers,
>>>>>>>> Steven
>>>>>>>>
>>>>>>>>
>>>>>>>>
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>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>>>
>>>>>>
>>>>>>
>>>>>>
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>>>>> +-----------------------------------------------------------------+
>>>>> |Paul Spencer pspencer at dmsolutions.ca |
>>>>> +-----------------------------------------------------------------+
>>>>> |Applications & Software Development |
>>>>> |DM Solutions Group Inc http://www.dmsolutions.ca/|
>>>>> +-----------------------------------------------------------------+
>>>>> ---------------------------------------------------------------------
>>>>> To unsubscribe, e-mail: webmap-discuss-unsubscribe at mail.osgeo.org
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>>>>
>>>>
>>>>
>>>> --Cameron Shorter
>>>> http://cameron.shorter.net
>>>>
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>>> +-----------------------------------------------------------------+
>>> |Paul Spencer pspencer at dmsolutions.ca |
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>>> |Applications & Software Development |
>>> |DM Solutions Group Inc http://www.dmsolutions.ca/|
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>>
>>
>> --Cameron Shorter
>> http://cameron.shorter.net
>>
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> |Paul Spencer pspencer at dmsolutions.ca |
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> |DM Solutions Group Inc http://www.dmsolutions.ca/|
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