[postgis-users] Using st_createarc(geometry, geometry, geometry, text)

[mzetka3 at tlen.pl]

Hello,
1. I need real example of use function st_createarc(startpoint geometry, endpoint geometry, arcenter geometry, direction text). Function came from this pdf: http://www.pgcon.org/2011/schedule/attachments/195_Using%20PostgreSQL%20for%20Flight%20Planning.pdf 
page: 33. 

2. I won't to use this to find route between two airports. And please explain me how to find third parameter which is arcenter-geometry. If it possible please give me example on airports LAX and CDG. 
LAX: 33.9425000	-118.4080556 (lat, lon)
CDG: 49.0127778	2.5500000 (lat, lon)

Thanks for the help!!
Mateusz