[Tagging] Elevation and height on vertical features

Martin Koppenhoefer dieterdreist at gmail.com
Fri Jan 8 19:15:54 UTC 2016

sent from a phone

> Am 08.01.2016 um 17:18 schrieb Greg Troxel <gdt at ir.bbn.com>:
> I don't think it makes sense to add datum tags and have heights in other
> datums.  That just pushes the work onto the data consumer and adds
> confusion.

the advantage for the mapper is that it is quite easy, you simply read an elevation off a sign and add the reference height system to the value. (yes, you have to know what is this reference height system, that's why the "quite" is there). I'd also prefer to have uniform values in the same system, but if the alternative to having a value in a local system is not having any value at all, I'd prefer the values in other datums (and marked as such).

FWIW, for most usages of these ele values it doesn't really matter if a value is 20 meters more or less, they are used to get a rough idea, not to be used in calculations where a meter more or less is important, i.e. this discussion is mostly theoretical...


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