[OSM-dev] osmarender+tiles at home projection bug

[Robert Hart]

> -----Original Message-----
> From: dev-bounces at openstreetmap.org
[mailto:dev-bounces at openstreetmap.org]
> On Behalf Of Frederik Ramm
> Sent: 14 February 2007 18:35
> To: dev at openstreetmap.org
> Subject: [OSM-dev] osmarender+tiles at home projection bug
> 
> Hi,
> 
>    just stumbled across
> 
> http://wiki.openstreetmap.org/index.php/Osmarender_bug
> 
> and tried to add details to that via the discussion page; but having
> looked at everything closely, I now believe that everything is correct
> and there *is* no tiling bug. Can anyone who is familiar with
> projection and tiling have a look and correct me?
> 
> I have read about this bug so many times, it must be somewhere, but I
> cannot see why ;-)

Isn't the bug simply that Osmarender and TilesGen.pl are using a subtly
different projection? 

Osmarender 
a) can't do proper trig and is using a simpler approximation to cos()
(this could be improved by adding more terms), and  
b) because you can't do a function call, is using a constant
transformation across a whole render.

I would guess it is the latter that causes the issue? The bigger the
tile the larger the issue. With some thought this could be worked around
in TilesGen.pl

Rob



This message has been scanned for viruses by MailControl - www.mailcontrol.com