On 31/07/18 02:33, Kevin Kenny wrote:
On Mon, Jul 30, 2018 at 11:39 AM Martin Koppenhoefer
<dieterdre...@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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