[OSM-talk] Need Help Bulk Uploading some POIs

[Andy Allan]

On Dec 12, 2007 3:23 PM, Bone Killian <vitki at bonius.com> wrote:
> David Earl wrote:
> >
> > Are you sure the data has the correct datum for the lat/lon values? A
> > different datum could account for offsets like this.
> >
> > David
> >
> Pardon my newbishness, but what's a datum?
>
> I know the file in question was described as being intended for import
> into Garmin / Magellan GPS units.  Could they be using a different datum
> than we are?

Since the world isn't a sphere, and continents also drift around,
there's different ideas about exactly where a given lat/long is. Most
GPSes (and OSM) use WGS84, but there's many other datums - especially
for regional data where it may be more convenient to assume your
continent isn't moving around rather than shifting all your POIs a bit
to the left every decade.

Cheers,
Andy