[webmap-discuss] OGC and google style tiling
Paul Spencer
pspencer at dmsolutions.ca
Fri Apr 14 08:42:44 EDT 2006
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 |
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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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>
>
> --
> Cameron Shorter
> http://cameron.shorter.net
>
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