Re: [Isis-wg] Latitude/Longitude Granularity in https://www.ietf.org/id/draft-shen-isis-geo-coordinates-03.txt

Peter Lothberg <roll@Stupi.SE> Wed, 23 August 2017 14:50 UTC

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From: Peter Lothberg <roll@Stupi.SE>
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To: "Acee Lindem (acee)" <acee@cisco.com>
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Subject: Re: [Isis-wg] Latitude/Longitude Granularity in https://www.ietf.org/id/draft-shen-isis-geo-coordinates-03.txt
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Acee,

I missed this message as it was just text encoded, no attachments, my
obsolete mail ui can't handle it...

>Hi Peter,
>
>We wanted to assure that milliseconds of latitude/longitude offer
>enough granularity for your applications. This slightly more than 3
>cm granularity for latitude and slightly less the 3 cm granularity
>for longitude. 
>
>Thanks,
>Acee

We have Geo coordinates to form a graph over the network, from cables
and ducts in the ground to the wiring inside a CO/POP/Datacenter.

As Vint Cerf says we need to bring IPv6 to the planet as soon as
March, what we need to future proof this is a format that allows for
the following;

([Galaxy,Solar System,Planet],)* [Operator], [World], [Lat, Long,
Height], [Time of Observation UTC in MJD with decimals]

  (MJD - Modified Julia Date)
  (Operator is the originator/maintainer of the data.)

The proposal is a good start but you lack some important things;

 - You need to be ale to express arbitrary resolution for Lat/Long.

   Depending on the use, you might want to truncate the resolution to
   not reveal the exact location of infrastructure, and then again you
   may want to express exactly where things are. 

   You need to be able to express what we can measure for lat/long
   as an example, so you have to be able to represent this in your
   format:

      LAT 59.317647949 North
      LON 18.023390835 East

- When it comes to height, we really have a problem;

  - Different countries have different ways of measuring the "sea
    level".
  - The sea level are rising
  - The land is also rising, like our Stockholm location is moving 
    about 11mm up and 7mm NE in average every year, so you need to 
    have a date on the observation of the position.
  - The local observations have different ages
  - GPS presented height is done with a theoretical model of the earth
    and calculated based on the distance from the GPS satellite.

   (Neighboring countries in some cases have more than 100cm
    difference in their definition of sea level.)

Height is a signed value, 1mm resolution, with a source identifier
(you need way to add new identifiers for the future);
       - WGS84
       - Local official survey
       - Local height (maybe from basement of building)
       - Local sequence number

- In some cases you want to describe something other than the natural world
  itself. e.g., a VPN described as a flat plane, or military / private
  tectical graph that is a different "plane" / "overlay" etc. 

  So we ended up with a Integer that represents the "world" you are
  describing and the vale of 0 represent the natural world we all live in
  and have as a common reference.

(*) - The astronomers refers to planets in our solar system with a
coordinate system with the sun as 0,0,0. Everything moves, continental
drift to ephemerides of planets and satellites. I chose to leave those
models out of scope as there is enough data in the proposed format to
go to other sources and augment the positions.


-Peter



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