[HN Gopher] Tissot's indicatrix
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       Tissot's indicatrix
        
       Author : unobatbayar
       Score  : 62 points
       Date   : 2024-02-02 13:05 UTC (1 days ago)
        
 (HTM) web link (observablehq.com)
 (TXT) w3m dump (observablehq.com)
        
       | enriquto wrote:
       | For a bit of context:
       | https://en.wikipedia.org/wiki/Tissot%27s_indicatrix
       | 
       | This is an essential tool to teach, not only map projections, but
       | the more general concept of Riemannian metrics!
       | 
       | See also the Dupin indicatrix, whose wikipedia article
       | unfortunately lacks good figures:
       | https://en.wikipedia.org/wiki/Dupin_indicatrix (it makes a funny
       | appeal to "just imagine them"...)
        
         | Our_Benefactors wrote:
         | Thank you. Without this, I was trying to understand how the
         | code snippets were related to the watch brand Tissot.
        
         | selimthegrim wrote:
         | I'd heard of a Dupin cyclide but not this, thanks.
        
       | rrr_oh_man wrote:
       | Somewhat related (if you're one of today's lucky 10,000):
       | 
       | https://xkcd.com/977/
        
         | 082349872349872 wrote:
         | or further afield, Spilhaus: https://www.esri.com/arcgis-
         | blog/wp-content/uploads/2019/09/...
        
         | omoikane wrote:
         | I was looking for Dymaxion in the dropdown list and it's not
         | there :(
         | 
         | It doesn't have Euler Spiral[1] either, but maybe that's
         | expecting too much.
         | 
         | [1] http://andersk.mit.edu/euler-spiral-projection/
        
       | hiyer wrote:
       | And here I was thinking this was a new watch from Tissot :-)
        
         | qubex wrote:
         | Same. What I found was far more interesting and educating.
        
         | king_magic wrote:
         | Ha, my first thought too. Some new kind of movement to follow
         | the Powermatic 80, perhaps?
         | 
         | But like someone else said, a very interesting read.
        
       | glutamate wrote:
       | Which language is used in the code boxes here? is this a
       | JavaScript extension?
        
         | glutamate wrote:
         | The answer is probably in here
         | https://observablehq.com/documentation/cells/observable-java...
         | but i still don't see why you can do `x = { let y = 5; return y
         | }`
        
           | FragenAntworten wrote:
           | I think that's a combination of two features, named cells[1]
           | and blocks[2].
           | 
           | [1] https://observablehq.com/documentation/cells/javascript#n
           | ami...
           | 
           | [2] https://observablehq.com/documentation/cells/javascript#e
           | xpr...
        
           | zokier wrote:
           | > Named cells look like, and function almost like, assignment
           | expressions in vanilla JavaScript
           | 
           | > But sometimes you want statements, such as for loops. For
           | that you'll need curly braces, and a return statement to give
           | the cell a value. Think of a cell as a function, except the
           | function has no arguments
           | 
           | So `x = { let y = 5; return y }` declares named cell x with
           | value from the return value of that function-like code block.
           | So basically that should be same as `x = 5`, which also is
           | named cell declaration and not JS variable assignment.
        
       | omoikane wrote:
       | See also:
       | 
       | https://observablehq.com/@d3/projection-comparison
        
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       (page generated 2024-02-03 23:01 UTC)