[okfn-labs] opening up what3words

willi uebelherr willi.uebelherr at gmail.com
Mon May 18 16:25:28 UTC 2015

Dear Maurizio.

 > The projection used is the "Google Web Mercator"
 > https://en.wikipedia.org/wiki/Web_Mercator

No, this projection don't exist. Only the Mercator Projection exist. And 
the people from Google use it.

The projection is the way, how we make the degree net of our planet as a 
ball visible in a 2D system. And we can use many different projection 
systems. Depend of our intention.

But the lat/lon coordinates are independent from that. Onle the mapping 
algorithm in a mathematical description are different. The results are 
different maps with different errors.

The target data are always the lat/lon coordinates. This are universal. 
And this we can transform in an understandable form. In a visual map or 
in a word sequence.

many greetings, willi
Cordoba, Argentina

Am 18-May-15 um 05:56 schrieb Maurizio Napolitano:
> from my point of view, a good solution may be to create a grid using
> the same method by using TMS - Tile Mapping Service.
> This is the same method used by OpenStreetMap, Google Maps and a lot
> of different webmapping providers\
> I a TMS you have differents kind of "floor" (each floor is a a zoom level).
> In this case I think, can be usefull use a zoom level 22 or more (the
> right number to have a tile of 3x3 meters or less).
> I suggest you to have a look here
> http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames
> With a TMS you identify a single tile with 3 number: zoom level, row and column.
> The projection used is the "Google Web Mercator"
> https://en.wikipedia.org/wiki/Web_Mercator
> but from the tile is possible transform in WGS84 (lat/log) coordinates
> The solution has some mistakes: but this is a with the projections!
> look here
> https://en.wikipedia.org/wiki/Web_Mercator#Advantages_and_disadvantages
> In my point of view:
> - it's impossible have a complete coverage of the world
> - the solution can forget the the cases of North and South pole, or
> create another solution for this cases
> - have a perfect precision is a big challenge: better concentrate to a
> solution with a reasonable error of precision (from ~5 meters). The
> precision depends on the use.
> If ask you "Where is London?" You don't need to have a perfect
> precision. It's always a big discussion define which is the point to
> describe a city: the main square? the downtown? the main building? the
> main symbol of the city? the social barycenter? ....
> Other case if I ask "Where is the headquarter of the OKFNlab?" maybe I
> need to know where is the building or the main entrance ...and so on.
> - onece created the grid, I suppose that, later is "easy" have a
> dictionary like what3words.
> Maybe by using some data like multiwordnet -
> http://multiwordnet.fbk.eu/english/home.php (cc-by license) and have a
> multi language "what3words" to give a name of each cell.

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