[Tiling] Fwd: [OSGeo-Standards] Irregular tile coverage in TMS?

[Paul Ramsey]

On Mon, Sep 13, 2010 at 10:26 AM,  <christopher.schmidt at nokia.com> wrote:
>
> On Sep 13, 2010, at 1:06 PM, ext Paul Ramsey wrote:
>
>> It looks like these discussions might add some notes and alterations
>> to the existing document, so I've set up a page to track them and
>> their status. Eventually this could result in a TMS 1.1 page.
>>
>> http://wiki.osgeo.org/wiki/Tile_Map_Service_Specification_Change_Requests
>
> It might make more sense to go to a '2.0' and align TMS with the 0,0 top left
> that everyone else has gone with. (WMTS, Commercial Providers, OSM, etc.)

For the record, back in the day, you were right and I was wrong (once
again proving that implementation trumps theory)... the reason I clung
to my math coordinates (and my guns and my religion) is that for most
map projections there is no "top left" (ie, the valid range of the
plane doesn't just cut out). However, forcing the definition of a
maximum bounds as part of the specification gets around this and then
we could still support all projections and also move from math
coordinates to image coordinates for tile numbering.

P

> -- Chris
>
>> P.
>>
>> On Mon, Sep 13, 2010 at 12:21 AM, Oliver Tonnhofer <olt at bogosoft.com> wrote:
>>> Hi,
>>>
>>> I think we need to differentiate between active and passive TMS implementations. When a tile is missing for an active implementation, it often means a cache-miss (unless the server knows more about the coverage) and the tile needs to be created. For passive implementations, i.e. bunch of static files, there is no way to create that tile.
>>>
>>> On 13.09.2010, at 04:12, Matt Priour wrote:
>>>> I think requiring servers to actually cache individual empty images for each empty tile is not useful.
>>>
>>> Well, that's an implementation detail. MapProxy can store symbolic links for all tiles that only contain one color (empty, water, forest, etc.). So you don't waste space, only inodes.
>>>
>>>> The server response, whether it is an no data image for each request, a redirect to a common no data image, or a simple 404; is not really all that important either. Clients should be able to handle any of those type responses and behave appropriately.
>>>
>>>
>>> Yeah, I agree with you, clients should be prepared to get different replies. But I would like to suggest that returning empty images should be 'best practice'.
>>>
>>> Regards,
>>> Oliver
>>>
>>>
>>>
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>