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<div class="moz-cite-prefix">On 2019-03-05 23:48, Warin wrote:<br>
</div>
<blockquote type="cite"
cite="mid:2aa79dfc-68c4-faf4-1cc5-047da9c2545c@gmail.com">
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<div class="moz-cite-prefix">On 05/03/19 21:30, Sergio Manzi
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:3e22a8de-45ff-48b4-a8f3-7150aa6668c6@smz.it">
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<p>On 2019-03-05 11:14, Warin wrote:<br>
</p>
<blockquote type="cite"
cite="mid:1954fe1d-e2a7-2545-f1ef-12d8945d6a22@gmail.com">On
05/03/19 20:08, Jean-Marc Liotier wrote: <br>
<blockquote type="cite">On Mon, March 4, 2019 11:20 pm, Warin
wrote: <br>
<blockquote type="cite"><a class="moz-txt-link-freetext"
href="https://wiki.openstreetmap.org/wiki/Proposed_features/antenna:use"
moz-do-not-send="true">https://wiki.openstreetmap.org/wiki/Proposed_features/antenna:use</a>
<br>
</blockquote>
This is a way to solve most of the problem, but it fails the
"map it as I <br>
see it" test. <br>
<br>
man_made=antenna + antenna:reflector=dish does map the
satellite <br>
communications antenna I just spotted... But what the naïve
mapper I am <br>
really wants is man_made=antenna + antenna=dish (or <br>
monopole/dipole/yagi/helical/phased_array ...) : "map it as
I see it" ! <br>
<br>
Then one can add antenna:propagation, antenna:application, <br>
antenna:propagation, antenna:polarisation etc. but they are
accessory. <br>
<br>
Am I mistaken in believing that the main tags chain should
focus on <br>
offering a straightforward way to map the apparent physical
features, <br>
rather than invisible distinctions ? Not that invisible
distinctions are <br>
not welcome too - but they should stay out of the way. <br>
</blockquote>
<br>
Sympathies! <br>
<br>
An alternative is available ... <br>
<br>
man_made=antenna <br>
<br>
dish=yes <br>
</blockquote>
<p>So far, so good.</p>
<p><br>
</p>
<blockquote type="cite"
cite="mid:1954fe1d-e2a7-2545-f1ef-12d8945d6a22@gmail.com">cross_gain_feed=yes
<br>
</blockquote>
<p>What does that mean? I'm a licensed radio amateur (<i>for
more than 30 years</i>) and I never heard of that term...
:-/<br>
</p>
</blockquote>
<br>
Arr casse grain ... apologies. (added word to spell checker) <br>
</blockquote>
<p><br>
</p>
<p>Ah, OK, a Cassegrain antenna, one with the Illuminator on (<i>or
close to</i>) the surface of the main concave reflector and a
secondary convex reflector. Amazing, but it takes the name from
the inventor of this design, Laurant Cassegrain, 1<b><u>6</u></b>29-1<b><u>6</u></b>93!!!
:-)<br>
</p>
<p><br>
</p>
<blockquote type="cite"
cite="mid:2aa79dfc-68c4-faf4-1cc5-047da9c2545c@gmail.com"> How is
the reflecting dish signal connected? There must be a real antenna
that does that. <br>
And then there is the way the antenna gets the reflected signal. <br>
<a class="moz-txt-link-freetext"
href="https://en.wikipedia.org/wiki/Parabolic_antenna"
moz-do-not-send="true">https://en.wikipedia.org/wiki/Parabolic_antenna</a><br>
<br>
<br>
<br>
There is a lot to learn, we should have more life times ...<br>
<br>
<blockquote type="cite"
cite="mid:3e22a8de-45ff-48b4-a8f3-7150aa6668c6@smz.it">
<blockquote type="cite"
cite="mid:1954fe1d-e2a7-2545-f1ef-12d8945d6a22@gmail.com">
two_way=yes <br>
</blockquote>
<p>Prove that!</p>
</blockquote>
As an example: This may be a TV studio where TV programs are
transmitted to a satellite for distribution. <br>
As a TV studio it may also receive TV signals from remote
broadcasts... or other TV studios connected to the satellite.</blockquote>
<p><br>
</p>
<p>I'm sure you understand that the above argument isn't worth a
dime: you only move the issue of "<i>knowing</i>" that an antenna
is a two ways antenna to the one of "<i>knowing</i>" that below
the antenna there is a production studio broadcasting stuff and
therefore there must be a two_ways antenna somewhere on the roof:
one of the probably many antennas up there. <br>
</p>
<p><br>
</p>
<blockquote type="cite"
cite="mid:2aa79dfc-68c4-faf4-1cc5-047da9c2545c@gmail.com"> OSM
accepts 'knowledge' as a suitable source of information. <br>
</blockquote>
<p><br>
Really? OSM accepts 'knowledge' as a suitable source of
information? Whose knowledge? How verifiable? I don't know if this
is really an official policy (<i>to me it seems to violate the
observability and verifiability principles</i>), but if it
really is (<i>is it?</i>), I tell you, I'm not interested in that
kind of information: in a GIS I only trust observable and
verifiable truths, even if you have all the rights to "map your
knowledge".</p>
<p><br>
</p>
<blockquote type="cite"
cite="mid:2aa79dfc-68c4-faf4-1cc5-047da9c2545c@gmail.com">
<blockquote type="cite"
cite="mid:3e22a8de-45ff-48b4-a8f3-7150aa6668c6@smz.it">
<blockquote type="cite"
cite="mid:1954fe1d-e2a7-2545-f1ef-12d8945d6a22@gmail.com">
satellite=yes <br>
</blockquote>
<p>Prove that! Because it points at the sky? There are many
other good reasons to point an antenna at the sky...<br>
</p>
</blockquote>
<br>
Again? If you don't know .. don't tag it. But don't deny others
from adding stuff they do know.<br>
<br>
Don't know that a road is closed in winter? then don't tag it.<br>
Know that a road is closed in winter - tag it.<br>
Come across an open road in summer that is tagged closed in winter
... and you want to verify the closure? Come back in winter or
contact the relevant mapper. <br>
</blockquote>
<p><br>
</p>
<p>Yes, sorry, again and again. Of course if I don't know something
I will not tag it, but I'm more concerned about those who thinks
or pretend to know and will tag "something" which is not generally
and easily verifiable.<br>
</p>
<p>If on the antenna on the roof there is a board stating "This is a
two_ways antenna" and on the road there is a board stating its
winter closure, I fully accept the tagging. If there is no such
board I don't trust that information, nor for the antenna, nor for
the road and I'll seek more reliable sources of information (<i>of
course the "boards" could be "virtual boards", such as
officially published information from the road/building operator</i>).<br>
</p>
<br>
<blockquote type="cite"
cite="mid:2aa79dfc-68c4-faf4-1cc5-047da9c2545c@gmail.com"> The
most common antenna people see are TV antennas, most pople know
what they are and can tag them at least the basics. Next would be
mobile phone antennas. After that they are not so well known, most
would have to look them up to find out what they are. <br>
</blockquote>
<p><br>
</p>
<p>Now tell me that you really expect (and hope) to map all TV
antennas in the world, on the roof of their respective buildings.
You understand we are in all likelihood talking of billions (10^9)
objects, do you? And you surely understand that such huge quantity
of information will cause inefficiencies (<i>and costs...</i>) for
the system.</p>
<p>I'm also very much unsure that a system like the OSM DB lends
particularly well to handle that kind of information in such huge
numbers. I think we would probably need a 3D object oriented GIS
system for that, and again a CAD system would probably be even
better at certain scales and for certain kind of information.<br>
</p>
<p>Also, if on the other hand you don't expect all TV antennas to be
mapped, what will be the value of such fragmentary and sparse
information? "<i>Cui prodest</i>"? Who is going to benefit from
such information? Those with a concrete interest in such
information will surely already have their accurate sources of
information and disregard our fragmentary and sparse information
of unknown accuracy.</p>
<p><br>
</p>
<p>Cheers!</p>
<p>Sergio<br>
</p>
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