[Tilesathome] Lowzoom Place Labels displaced

[Jiri Klement]

I think the correct way to do projection is:

y1 = mercator(minlat)
y2 = mercator(maxlat)
y = (mercator(lat) - y1) / (y2 - y1)

mercator is ln (tan(lat) + sec (lat))  (from wikipedia).

y will be in interval 0..1. We can multiplicated it by some coefient.
The best would be size of tile in pixels, because it will allow to
share css definition beetween zoom levels.

But I don't know much about projects, this is just what I got from wiki.

On Fri, Sep 19, 2008 at 10:52 AM, Rob Reid <rob at robreid.co.nz> wrote:
> Sorry, replied to spaetz rather than list.
>
> Sebastian Spaeth wrote the following on 19/09/2008 19:20:
>>> Perhaps it makes no different on z12 (I think deelkar once calculated
>>> that it's half a pixel in z12 or so) and then we can skip this on
>>> osma. But fixing this in orp so we can do lowzoom captions would
>>> still be great.
>>>
> I'm not convinced what I'm seeing is the same as the projection problem
> we saw ages back in osma is it?
> Have a look the spot where I first noticed what I'm seeing.
> http://www.openstreetmap.org/?lat=-42.403&lon=173.685&zoom=11&layers=0B00FTF
>
>
> At z12 Kaikoura is where I expect it, if you zoom out one lvl to z11 you
> can see the big offset. If you zoom out to z10 the offset stays about
> the same.
>
> Why is there such a big jump in offset from z12 to z11?
>
> This is the screen shot I previously mentioned that I took around the
> 15th August when I could see two captions.
> http://www.flickr.com/photos/29556472@N03/2763631947/
>
> The name that is offset is from a freshly generated caption layer, the
> correctly placed name is from a previously generated lowzoom. Why would
> the name be correctly placed before the 15th and offset after it?
>
> I was generating caption layer for z6-11 for New Zealand around the 15th
> Aug and it seemed to me that everything went from not being offset to
> being a few miles south at that point.
> That's what made me wonder if it was a client problem in or/p that was
> introduced about the time the proximity filter was added  which was the
> 6th Aug.
>
> rcr
>
>
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