[Proj] Projection Dev - How to call other projections from aprojection?

[Noel Zinn (cc)]

>From the Geodetic Glossary, NGS, NOAA, 1986



“spheroid 



(1) Any surface differing but little from a sphere, (2) An ellipsoid of revolution, (3) A surface derived, by use of a standard formula for the Earth's potential, by giving the potential one specific value (Such a surface is intended to be an approximation to the geoid), (4) By extension, a surface close to the geoid or approximating the geoid.  



Although sense (2) has been widely used in geodetic literature, modern practice is to employ "ellipsoid of revolution" as a specific figure, and "spheroid" in sense (1) as a general term.  Many reference ellipsoids of older vintage have been called spheroids (e.g., Bessel spheroid) and are so listed in this glossary.”


Noel Zinn, Principal, Hydrometronics LLC
+1-832-539-1472 (office), +1-281-221-0051 (cell)
noel.zinn at hydrometronics.com (email)
http://www.hydrometronics.com (website)


From: Michael P Finn 
Sent: Monday, October 10, 2011 1:24 PM
To: PROJ.4 and general Projections Discussions 
Cc: proj at lists.maptools.org ; proj-bounces at lists.maptools.org 
Subject: Re: [Proj] Projection Dev - How to call other projections from aprojection?


Interesting. 

So where is a threshold (that turns a spheroid into an ellipsoid)? Technically all spheroids are ellipsoids, mathematically. (Further, a sphere is also an ellipsoid whose semi-major and semi-minor axes are identical.) 




      From:  Charles Karney <charles.karney at sri.com>  
      To:  <proj at lists.maptools.org>  
      Date:  10/10/2011 07:34 AM  
      Subject:  Re: [Proj] Projection Dev - How to call other projections from        aprojection?  
      Sent by:  proj-bounces at lists.maptools.org 


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This may be true is cartography.  It's only partly true in geodesy --
some authors make a distinction, e.g.,

  W. A. Heiskanen and H. Moritz, Physical Geodesy,
  (Freeman, San Fransisco, 1967)

use spheroid to refer to an approximately spherical shape.  (This was,
presumably, its original meaning.)


On 10/09/11 19:43, Noel Zinn (cc) wrote:
> "Spheroid" and "ellipsoid" are synonyms for the same thing in geodesy and
> cartography.
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