[Proj] Re: Newbie Polar stereographic question
Gerald I. Evenden
gerald.evenden at verizon.net
Thu Jul 13 10:49:30 EDT 2006
On Thursday 13 July 2006 2:13 am, john star wrote:
> Hi Gerald!
>
> Thanks, I understand now that in libproj, the plane MUST be orthogonal
> to the earth, and there is no support for this plane to be "inside" the
> earth..
In a sense, yes. Using a scaling factor (k or k_0) of less than 1 turns the
projection plane into a secant plane.
> Is there a way to use the library for this case ? by playing with
> parameters (btw,
> what are the rest of parameters like lat_ts and k?), or it is just not
> supported ?
+lat_ts is used for the polar aspects and denotes the latitude at which the
scale is 1 (the place where the secant plane intersects the surface).
> Best Regards
> John
>
> >Basically. The source point of all the rays is the "antipod" of the point
> >of tangency of the projection plane. That is at a point -lat_0,-lon_0.
>
> I should say lon_0+180
>
> >Thus the ray from the ray source to lat_0, lon_0 passes through the center
> >of the earth. And the plane of the projection is orthogonal to this ray.
>
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