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<div class="moz-cite-prefix">On 8/01/2016 9:56 AM, Colin Smale
wrote:<br>
</div>
<blockquote
cite="mid:23A0EB40-4CA1-4C60-A75A-FF3079DDCC8F@xs4all.nl"
type="cite">Nobody will be using the raw data to fly a plane. It
doesn't matter if we use the ele tag for the top or the bottom -
as long as the height is given, the other value can easily be
derived. What is important is consistency, both in its definition
and it's usage. Defining it as sometimes the top and sometimes the
bottom of a feature doesn't help.<br>
</blockquote>
<br>
And consistent with other mapping products/practices? <br>
<br>
By convention maps uses blue to indicate sea, rivers and streams. <br>
The idea is to be readily usable by using the same practice as
others have used in the past.<br>
Not to set some new standard where there is no reason for it. <br>
<br>
Grasping at straws .. the elevation of a mountain is given as its
peak. If there is consistency within the map then the elevation of
all objects should be their maximum height. <br>
<br>
<blockquote
cite="mid:23A0EB40-4CA1-4C60-A75A-FF3079DDCC8F@xs4all.nl"
type="cite">
We will also need to standardize on a datum for elevations. The
wiki refers to both mean sea level (which varies by country) and
wgs84. The differences might be enough to take the wheels off your
plane..<br>
</blockquote>
<br>
Good point there! <span class="moz-smiley-s1"><span> :-) </span></span><br>
For most it won't matter. What do international planes use as there
reference for height? Use that - again consistency. <br>
<br>
By maintaining some consistency with what has been done elsewhere it
will make it easier to compare, check and confirm OSM data. <br>
<blockquote
cite="mid:23A0EB40-4CA1-4C60-A75A-FF3079DDCC8F@xs4all.nl"
type="cite">
<br>
<br>
<div class="gmail_quote">On 7 January 2016 22:50:02 CET, Warin
<a class="moz-txt-link-rfc2396E" href="mailto:61sundowner@gmail.com"><61sundowner@gmail.com></a> wrote:
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<pre class="k9mail">On 8/01/2016 3:32 AM, Christoph Hormann wrote:
<blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #729fcf; padding-left: 1ex;"> On Thursday 07 January 2016, Aaron Spaulding wrote:
<blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ad7fa8; padding-left: 1ex;"> Hi all,
I’ve been working on generating 3D meshes based on OSM data and I ran
into a problem. Vertical features like 'natural=cliff',
'barrier=retaining_wall’ and 'waterway=waterfall' occupy two points
in physical space, but because of the 2D nature of OSM its ambiguous
which side of the feature that the ‘ele’ tag applies.
</blockquote> For cliffs mapping conventions say that you should put the line on top
of the cliff in case it is not exactly vertical - accordingly the ele
tag would also refer to the top - but keep in mind that the elevation
does not
have to be constant.</blockquote>
Consider who is going to use the map, and for what purpose.
The most critical use is for aeroplanes .. where the maximum height is
critical information!
I think for that reason alone most maps should indicate the maximum
elevation of an object.
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</pre></blockquote></div>
</blockquote>
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