[OSM-dev] Timestamp in PBF files

[Jochen Topf]

On Wed, Nov 21, 2012 at 11:50:38AM +0100, marqqs at gmx.eu wrote:
> > How many nodes in the planet lack a latitude or longitude? Using a MAXINT
> > encoding will cost about 8 bytes for each missing latitude or longitude.
> >  It's possible to reduce this to 2-3 bytes, but the format gets
> > uglier/hackier. IMHO, probably not worth that cost.
> 
> As far as I understood, only nodes with the attribute action=delete do not have (resp. do not need) lon/lat. On the other hand, it does not hurt to give them false lon/lat values. This is what osmconvert does when you apply the --fake-lonlat option.
> 
> In PBF, lon/lat are delta coded, aren't they? Thus it would be best to write a delta of 0, i.e., to take the logical value of the previous node. A few steps later in the toolchain lon/lat values of action=delete objects will be deleted anyway (together with their objects).

You only have missing lon/lat in OSM files with history. And presumably you
use them because you want to know when what objects were created and deleted
and so on. So you can not just ignore deleted objects. And you want to know
whether an object had no lon/lat as compared to the lon/lat of the object
that happened to be right before it in the file. So your solution doesn't
work.

Jochen
-- 
Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/  +49-721-388298