[Openstreetmap] speed, at last

[Lars Aronsson]

Mikel Maron wrote:

>  I'm not certain what happened last night, but it sounds like 
>  the OnEarth server must have gone down for some time. The 
>  satellite imagery is now showing up in the editor.

The state of "white speed" only lasted for five minutes.

> I've been corresponding with the maintainer of the OnEarth WMS. 
> It may soon be possible for OSM to run its own local cache of 
> Landsat. He has produced a tiling system that only takes up 
> 300Gb of space, which is very affordable. This will speed things 
> up considerably, and is generally a very exciting development

How does it work today?  If we're not running our own local cache 
of the Landsat images, where do they come from?  Are they pulled 
live from some remote server?  What is OnEarth and how are they 
involved?  And what are the sizes today, that are bigger than 300 
GB?  It should be possible to keep sizes down by only storing the 
areas that are used, i.e. worldwide coverage in the uppermost zoom 
levels, and only spotty coverage (Western Europe and little else) 
of the finer details.

I would have guessed that the satellite image tiles are the same 
for the AJAX viewer and the Java applet, using the same cache for 
the generated tiles (before white lines or yellow dots are added), 
so viewing at zoom=15 would fill the cache that can then be used 
for fast editing.  But I cannot say that this assumption is 
supported by my experience.  At times (particularly in the 
afternoon, European time) the tiles appear only very slowly in the 
edit applet.


-- 
  Lars Aronsson (lars at aronsson.se)
  Aronsson Datateknik - http://aronsson.se