Why geo_distance is filtering in elliptical shape?

Hi, I' ve tried both with no effect.

Dne pondělí, 16. dubna 2012 18:26:17 UTC+2 Igor Motov napsal(a):

Are you using "plane" distance_type or "arc" distance_type?

On Monday, April 16, 2012 12:11:59 PM UTC-4, Ondřej Bílka wrote:

Hello,
I have an ES database of GEO objects and I need to search the nearest
objects around some geo_point in custom distance and show them on Google
Map.
I'm using geo_distance filter, everything works perfect, but I have
recognized, that the filter is not filtering in circullar-like distance (in
exact X km radius), but in some elliptical shape. For better understanding
I've attached screenshots. I'd like to create google circle on the map to
show the border of distance, but now it is not accurate because the
ellipse.
I don't know the reason, why it is like that, or if I'm doing something
wrong. Or is it bug?

Unfiltered Objects

Filtered

https://lh3.googleusercontent.com/--Gp7lcyF99E/T4xDv7q7bDI/AAAAAAAAADI/vHp3tPIkEmI/s1600/filtered2

Filtered - lower zoom to better recognizing the ellipse, on both left and
right side of the inner circle should be some objects too

https://lh5.googleusercontent.com/-i_kcJfe9Paw/T4xD8PwsNUI/AAAAAAAAADU/Mq_7oF_EgqI/s1600/filtered

Many thanks for explanation!