[OSM-dev] "Retina" tiles - best way to support them?

Martin Koppenhoefer dieterdreist at gmail.com
Thu Jul 5 09:32:28 BST 2012


2012/7/5 Frederik Ramm <frederik at remote.org>:
> I'd be interested in hearing from users of high-resolution displays if these
> big tiles actually make a difference (except being slower to load...).


actually it doesn't make any difference on an iPhone4 (960x640px), I
guess at least with this particular OL settings they are displayed at
50% like on your desktop.

Btw.: the tiles are NOT identical also apart from the resolution, look
e.g. at Fürth: on the normal tiles there is Erlangen above it, while
on the hires tiles it isn't.

On the other hand it wouldn't even be desirable (IMHO) to have the
exact same tile at a higher resolution. To make best benefit from more
pixels on the display it would be ideal to have a dedicated style to
be able to get more details on the "same" zoom level. Something in
between the detail level of the normal style (currently too small) and
the next zoom level would be nice (so you wouldn't only get a crisper
view but also slightly more detail).

Another thing is that on mobile devices traffic and loading speed are
often an issue, and upscaled images (standard tiles at 200%) are
generally "sufficient" for most users I guess, with the benefit of
fewer data to be transfered (and cached!). Especially when it comes to
offline tiles of bigger areas the increase in memory consumption of
those hires tiles is significant (around 3 times on a rough estimate
with your tiles).

To overcome these issues rendering on the device could be a solution
(not sure what this means in terms of increased battery consumption),
or maybe a hybrid approach (hillshading and contours / area fills
prerendered, overlayed with vector roads and pois). This would even
lead to a native stepless zooming experience (like a WMS), and the
vectors could maybe be used for other things as well (routing (?),
feature search and highlighting).

cheers,
Martin



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