rendering minor issue, South and North Pole

[Pedro Melo]

Well, if you zoom in really deep on one of the poles and center the
pole in the view window, and then you zoom out until you can see
almost the entire planet, a black disk will appear.

You can see a snapshot here:
http://pedro.melo.silva.googlepages.com/render.jpg

[fraser]

Hi Pedro,

This is because Google Earth uses Simple Cylindrical projection with a
WGS84 datum for its imagery base.
Whilst this produces excellent results for most of the globe at the
points where lines of longitude converge (north/south poles) you will
get the rendering anomalies you see.
Some time you get a flower like shape, some times a hole or black
disk...

(In simple terms they are wrapping a flat rectangle onto an
ellipsoid...imagine trying to wrap a football with a sheet of paper!)

You could always use a image overlay on the areas if you need to view
them.

Here, for instance, is an example of an overlay of the arctic region.
http://bbs.keyhole.com/ubb/download.php?Number=1000814

Hope this explains it.

Regards,

Fraser

[jpwade_bsu]

Hello Fraser,

Gerardo64's idea for polar projections is pretty nifty.

His forum post of the kml you reference is:
http://bbs.keyhole.com/ubb/showthreaded.php/Cat/0/Number/1000814

jpwade
www.czmartin.com/jpw

On Aug 1, 3:17 am, fraser wrote:
> Hi Pedro,
>
> This is because Google Earth uses Simple Cylindrical projection with a
> WGS84 datum for its imagery base.
> Whilst this produces excellent results for most of the globe at the
> points where lines of longitude converge (north/south poles) you will
> get the rendering anomalies you see.
> Some time you get a flower like shape, some times a hole or black
> disk...
>
> (In simple terms they are wrapping a flat rectangle onto an
> ellipsoid...imagine trying to wrap a football with a sheet of paper!)
>
> You could always use a image overlay on the areas if you need to view
> them.
>

> Here, for instance, is an example of an overlay of the arctic region.http://bbs.keyhole.com/ubb/download.php?Number=1000814

>
> Hope this explains it.
>
> Regards,
>
> Fraser
>
> On Aug 1, 12:22 am, Pedro Melo wrote:
>
>
>
> > Well, if you zoom in really deep on one of the poles and center the
> > pole in the view window, and then you zoom out until you can see
> > almost the entire planet, a black disk will appear.
>

> > You can see a snapshot here:http://pedro.melo.silva.googlepages.com/render.jpg- Hide quoted text -
>
> - Show quoted text -

[professormp3]

Hi All,
Something is definitely funny at the poles. Take a look, the patch
starts exactly from the 80 degree lines of latitude for both north and
south poles. If Fraser is correct then the patch will not have a
clearly defined line where it cuts off at the 80 degree line. Also I
think you all should look on the net for Admiral R Byrd's log of his
trip to the north pole and read it. Have you wondered why there is
open sea at the pole? There is ice farther south but as one goes up to
the pole the ice melts? Interesting isn't it? Its supposed to get
colder not warmer as one goes farther north. Back to Fraser.... you
mean no satellites fly over the poles to take any pictures? I doubt it
and if it is so then why? Why with so much technology they have to
take pictures from other satellites and wrap the image like a
football. Also think about it....lines of longitude have nothing to
do with satellites taking pictures of the earth. If I take a picture
of a football it will not matter how that football is devided.
Anyway I have emails where I contacted the librarian at cambridge
university for polar regions and they are VERY interesting.
Bye for now

On Aug 2, 10:37 pm, jpwade_bsu wrote:
> Hello Fraser,
>
> Gerardo64's idea for polar projections is pretty nifty.
>
> His forum post of the kml you reference is:http://bbs.keyhole.com/ubb/showthreaded.php/Cat/0/Number/1000814
>
> jpwadewww.czmartin.com/jpw
>
> On Aug 1, 3:17 am, fraser wrote:
>
>
>
> > Hi Pedro,
>
> > This is because Google Earth uses Simple Cylindrical projection with a
> > WGS84 datum for its imagery base.
> > Whilst this produces excellent results for most of the globe at the
> > points where lines of longitude converge (north/south poles) you will
> > get the rendering anomalies you see.
> > Some time you get a flower like shape, some times a hole or black
> > disk...
>
> > (In simple terms they are wrapping a flat rectangle onto an
> > ellipsoid...imagine trying to wrap a football with a sheet of paper!)
>
> > You could always use a image overlay on the areas if you need to view
> > them.
>
> > Here, for instance, is an example of an overlay of the arctic region.http://bbs.keyhole.com/ubb/download.php?Number=1000814
>
> > Hope this explains it.
>
> > Regards,
>
> > Fraser
>
> > On Aug 1, 12:22 am, Pedro Melo wrote:
>
> > > Well, if you zoom in really deep on one of the poles and center the

> > >polein the view window, and then you zoom out until you can see

> > > almost the entire planet, a black disk will appear.
>

> > > You can see a snapshot here:http://pedro.melo.silva.googlepages.com/render.jpg-Hide quoted text -
>
> > - Show quoted text -- Hide quoted text -

[fraser]

Hi professormp3,

You're right, it's all a conspiracy, it has nothing to do with
projections and datums or any of that.
The Google engineers had to leave out the polar region because a race
of super beings commanded them to on pain of death.

Phew, I'm so glad the truth is finally out!


F.

> > > > You can see a snapshot here:http://pedro.melo.silva.googlepages.com/render.jpg-Hidequoted text -

[professormp3]

Strange eh... I never said anything about beings of any kind nor
duress of any kind. All I said was there is something funny at the
poles. I do not know what. I just find it strange that one cannot see
the poles at exactly the same latitude upwards. Well to each his own I
guess. I am not putting down your explanation. I am just stating my
views on the matter. As to whom is correct I do not know. Anyway thats
my view. Laters.
Professormp3

On Sep 21, 11:38 am, fraser wrote:
> Hi professormp3,
>
> You're right, it's all a conspiracy, it has nothing to do with
> projections and datums or any of that.
> The Google engineers had to leave out the polar region because a race
> of super beings commanded them to on pain of death.
>
> Phew, I'm so glad the truth is finally out!
>
> F.
>
> On Sep 21, 5:54 am, professormp3 wrote:
>
>
>
> > Hi All,
> > Something is definitely funny at the poles. Take a look, the patch
> > starts exactly from the 80 degree lines of latitude for bothnorthand
> > south poles. If Fraser is correct then the patch will not have a
> > clearly defined line where it cuts off at the 80 degree line. Also I
> > think you all should look on the net for Admiral R Byrd's log of his

> > trip to thenorthpoleand read it. Have you wondered why there is
> > open sea at thepole? There is ice farther south but as one goes up to
> > thepolethe ice melts? Interesting isn't it? Its supposed to get
> > colder not warmer as one goes farthernorth. Back to Fraser.... you

> > > > > You can see a snapshot here:http://pedro.melo.silva.googlepages.com/render.jpg-Hidequotedtext -