Polar Stereographic projection Extent

[Ryan Ollerenshaw]

Vincent J. Troisi wrote:
> Ryan Ollerenshaw wrote:
>> I am having a bit of trouble figuring out the extent I should use to 
>> display the entire northern hemisphere using the Polar Stereographic 
>> projection.  The best that i have been able to come up with is:
>>
>> EXTENT 3000 2000 4000000 3000000
>>
>> but this only displays the right half of the norther hemisphere, how 
>> can i display the full 360 degrees of the northern hemisphere all at 
>> one time?  When using a polar projection i am not sure what the 
>> extent numbers actually represent.  They cant be corner points 
>> because the display should be a circle, so what are they offsets 
>> from?  Any clarity that someone can provide on how to use polar 
>> projection would be very helpful. Thanks.
>>
>> PROJECTION     "proj=stere"
>>        "lat_ts=75"
>>        "north"
>>        "lat_0=90"
>>  END
>>
> We've been successful with
>
> -9036842.762, -9036842.762, 9036842.762, 9036842.762

when i try this extent i get a white circle that takes up most of the 
screen and i can only see a very small piece of my data in a half moon 
shape on the right edge of my window.  Is anyone able to explain what 
the extent numbers actually mean when using a polar projection?  Why am 
i getting a large white circle with my data wrapped around, and how do i 
decrees the size of this central circle to zero so my pole comes 
together to a single point?