[OSM-talk] OTG rule, borders & mountains existing | Re: Crimea situation - on the ground

[Colin Smale]

On 2020-02-14 10:18, Martin Koppenhoefer wrote:

> Am Do., 13. Feb. 2020 um 08:41 Uhr schrieb Colin Smale <colin.smale at xs4all.nl>: 
> Locations are stored in OSM as pairs of {lat,lon} and I assume these are both 64-bit floats in the database. 
> 
> AFAIK they are stored as integers (shifting the decimals)
> 
> If so then then my comments about preserving precision still apply to all "client" software and I bet the majority uses float. Then an innocent update to a tag on a node can end up unintentionally moving the location slightly, losing precision.

My comment about precision lost through conversion was not about missing
floating point digits, but about conversions from one CRS to another,
where you may need additional (proprietary) grid parameters to do a high
precision conversion. 

Yes I realise that but attention must be paid to all possible sources of
precision leakage. 

What use would proprietary parameters be? If they were used, are
relevant and kept private, this would impede the consumption of the data
by any clients. All GIS files must include, by value or by reference,
the relevant CRS, otherwise the contents can not be interpreted
properly, can they? Or are you thinking of the situation in China where
they have a state-controlled/licenced transformation?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk/attachments/20200214/ce22bb25/attachment.htm>