[Tagging] "satellit"

Sergio Manzi smz at smz.it
Wed Mar 6 01:38:34 UTC 2019

On 2019-03-05 23:48, Warin wrote:
> On 05/03/19 21:30, Sergio Manzi wrote:
>> On 2019-03-05 11:14, Warin wrote:
>>> On 05/03/19 20:08, Jean-Marc Liotier wrote:
>>>> On Mon, March 4, 2019 11:20 pm, Warin wrote:
>>>>> https://wiki.openstreetmap.org/wiki/Proposed_features/antenna:use
>>>> This is a way to solve most of the problem, but it fails the "map it as I
>>>> see it" test.
>>>> man_made=antenna + antenna:reflector=dish does map the satellite
>>>> communications antenna I just spotted... But what the naïve mapper I am
>>>> really wants is man_made=antenna + antenna=dish (or
>>>> monopole/dipole/yagi/helical/phased_array ...) : "map it as I see it" !
>>>> Then one can add antenna:propagation, antenna:application,
>>>> antenna:propagation, antenna:polarisation etc. but they are accessory.
>>>> Am I mistaken in believing that the main tags chain should focus on
>>>> offering a straightforward way to map the apparent physical features,
>>>> rather than invisible distinctions ? Not that invisible distinctions are
>>>> not welcome too - but they should stay out of the way.
>>> Sympathies!
>>> An alternative is available ...
>>> man_made=antenna
>>> dish=yes
>> So far, so good.
>>> cross_gain_feed=yes
>> What does that mean? I'm a licensed radio amateur (/for more than 30 years/) and I never heard of that term... :-/
> Arr  casse grain ... apologies. (added word to spell checker)

Ah, OK, a Cassegrain antenna, one with the Illuminator on (/or close to/) 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*_6_*29-1*_6_*93!!!  :-)

> How is the reflecting dish signal connected? There must be a real antenna that does that.
> And then there is the way the antenna gets the reflected signal.
> https://en.wikipedia.org/wiki/Parabolic_antenna
> There is a lot to learn, we should have more life times ...
>>> two_way=yes
>> Prove that!
> As an example: This may be a TV studio where TV programs are transmitted to a satellite for distribution.
> As a TV studio it may also receive TV signals from remote broadcasts... or other TV studios connected to the satellite.

I'm sure you understand that the above argument isn't worth a dime: you only move the issue of "/knowing/" that an antenna is a two ways antenna to the one of "/knowing/" 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.

> OSM accepts 'knowledge' as a suitable source of information.

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 (/to me it seems to violate the observability and verifiability principles/), but if it really is (/is it?/), 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".

>>> satellite=yes
>> Prove that! Because it points at the sky? There are many other good reasons to point an antenna at the sky...
> Again? If you don't know .. don't tag it. But don't deny others from adding stuff they do know.
> Don't know that a road is closed in winter? then don't tag it.
> Know that a road is closed in winter - tag it.
> 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.

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.

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 (/of course the "boards" could be "virtual boards", such as officially published information from the road/building operator/).

> 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.

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 (/and costs.../) for the system.

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.

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? "/Cui prodest/"? 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.



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