[Tiling] Fwd: [OSGeo-Standards] Irregular tile coverage in TMS?
arne at tiledmarble.org
Sun Sep 12 14:31:06 EDT 2010
My interpretation would be that 404 is the closest thing to a correct
response, at least if you want TMS to function the same way when served
from a directory of static files.
In GeoWebCache you can create b) using request filters, and the requests
that land on blank tiles result in a transparent PNG. That was mostly
for WMS-C's sake, where you can't return 404 and instead would have to
standardize a new OGC exception.
A transparent PNG is only some 200 bytes, which is usually comparable to
the HTTP overhead. The trouble with redirecting is that if you use a 301
the browser caches the redirect for as long as the target is valid, and
if you use a 302 it will recheck the redirect every time. (Only tested a
few browsers.) I stuck to sending the image each time with the same
expiration time as regular tiles.
On 9/12/10 1:33 PM, Mateusz Loskot wrote:
> I have posted a little question about TMS spec to the standards,
> but perhaps I could receive some feedback here as well:
> -------- Original Message --------
> Subject: [OSGeo-Standards] Irregular tile coverage in TMS?
> Date: Sat, 11 Sep 2010 19:46:51 +0200
> From: Mateusz Loskot<mateusz at loskot.net>
> To: standards at lists.osgeo.org
> I'm reading the TMS spec which says:
> "a coverage of regularly sized and spaced images that taken together
> form a complete visual representation of the entire area of coverage"
> I understand the size and spacing constraints.
> What I'm missing, however, is what TMS says about "topological"
> regularity of tiles within a coverage.
> I attached basic drawing with two example tile coverages:
> a) blue - regular coverage, rectangular
> b) red - irregular coverage
> Is only blue version kosher for TMS or both versions are valid?
> Best regards,
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