[mkgmap-dev] Different routing results using osm vs osm.pbf

Tue Oct 19 22:19:50 BST 2010

On Tue, Oct 19, 2010 at 3:06 PM, Steve Ratcliffe <steve at parabola.me.uk>wrote:

> On 19/10/10 15:58, Carlos Dávila wrote:
> > Yesterday I tested pbf input for mkgmap for the first time. Map was
> > built apparently without errors, but using the resulting map on
> > MapSource I get a suboptimal route, compared with the one I get using
> > osm as input. I used portugal.osm and portugal.osm.pbf from geofabrik
> > for the test. Today geofabrik is offering corrupt excerpts, so I can't
> > make further tests by now.
>
> That is interesting.
>
> If the .osm and .osm.pbf contain the same data then mkgmap should
> produce exactly the same map in both cases ignoring timestamps
>

> if you add --preserve-element-order in both cases.
> In the cases I tested this was true.
>

The results should be identical comparing OSM versus PBF with or without
that flag. Converting from osm to pbf with the default flags should preserve
everything in the origional OSM file, including precision of coordinates,
element order, metadata, tags, timestamps, etc. (The format offers some
options that produce smaller filesizes at the cost of not preserving
everything, but those are not on by default.). If there are any differences
between maps with and without --preserve-element-order, that is something
related to mkgmap, not PBF.

>
> If it doesn't then it is a bug.
>

Agreed.

Could it be a round-off error? I do all arithmetic in integers, only
multiplying against .000000001 at the very end.

Scott
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