Re: [boost] preview of a template geometry library

From: Schrader, Glenn (gschrad_at_[hidden])
Date: 2008-01-31 13:51:08

> -----Original Message-----
> From: boost-bounces_at_[hidden] [mailto:boost-bounces_at_[hidden]]
> On Behalf Of Barend Gehrels
> Sent: Thursday, January 31, 2008 11:55 AM
> To: boost_at_[hidden]
> Subject: Re: [boost] preview of a template geometry library
>
> Hervé,
>
> Thanks for your reaction. I will consider the separation of core
> geometry and more GIS-like geometries, and will study on your idea of
> coordinate-free geometries.
>
> We had the feeling that a library user or implementer can always
> speciliaze for other points than x-y, so it would work, but indeed if
> you have to redo all algorithms for latlong it is quite a job.

Another wrinkle for latlon conversion is that there are two different latitudes. This results from the earth being an ellipsoid rather than a sphere (centrifugal force makes the equator bulge out more than the poles). The "geodetic" latitude is the angle from the equator to a line perpendicular to the local earth surface. The "geocentric" latitude is the angle is from the equator to a line that intersects the center of the earth. The geodetic latitude is the one used most often but there are uses for the other one.

-ges