[Tagging] Let's get (quite) rid of units and their multiples in OSM values
61sundowner at gmail.com
Mon Jul 30 21:44:33 UTC 2018
On 31/07/18 02:33, Kevin Kenny wrote:
> On Mon, Jul 30, 2018 at 11:39 AM Martin Koppenhoefer
> <dieterdreist at gmail.com> wrote:
>> I did not check any numbers, but I would also expect a lot of data not following this definition.
> [of the ele=* tag meaining EGM96]
> Uhm, yeah. I've been using NAVD88 as orthometric datum. I have the
> tables loaded in my
> GPS app, and it's what surveyors use locally. But the difference
> between that and EGD96
> is far too small for my equipment to measure - I don't have a
> survey-grade GPS, or the
> patience for the integration time that using one requires.
> Entering ellipsoidal height rather than orthometric elevation, though,
> is Just Plain Wrong -
> and I bet we have a lot of data entered that way that are off by tens of metres.
> I further bet that two-thirds of the people reading this thread have
> Absolutely No Idea
> what we're talking about. (That isn't really a severe criticism. It's
> more an indictment
> of the sorry state of consumer-grade GPS that ordinary mappers would
> be forced to
> learn that much geodesy to get it right.)
+1 .. who has little idea of what your talking about :)
But then I don't usually play with elevation data, so I am not involved in it.
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