[mkgmap-dev] [PATCH v1] Better rounding in mkgmap

Tue Aug 11 16:37:13 BST 2009

Hi Clinton,

On Tue, Aug 11, 2009 at 05:13:04PM +0200, Clinton Gladstone wrote:
> On Tue, Aug 11, 2009 at 3:50 PM,
> Elrond<elrond+openstreetmap.org at samba-tng.org> wrote:
> 
> > As rounding seems a current topic, I'm throwing in a patch
> > that is sitting in my tree for a while now:
> 
> How can I best test this patch? Is there something I can look for
> without examining the binary data of the generated map? (For example,
> what are typical symptoms of incorrect rounding?)

"incorrect" is probably too hard (except for the very
special case, where I needed the better rounding).
"suboptimal" would be a better term.

To be honest, I don't know for sure how to really pin-point
it. My idea on this:

Set mapsource to "low detail" so that you get low
resolution data even when zoomed in somewhat. Zoom in until
the residential roads just apear and zoom out once (so that
they disappear again). That way you get some lower
resolution and should be able to see the
"raster"-resolution of the points used to make up all the
lines. About one fourth should be a little off relative to
the others with my patch, I'd say...

If you then switch the detail to "highest" to see the data
with more resolution but at the same zoom, you should see
the differences. Without the patch, maybe a few are farer
away from the "real" position than with the patch.

I hope this makes some sense to you...

Cheers

    Elrond