You can have that location line happen before the mission starts by puting it in the description file:
onLoadintro="C 3/435 ID, hill 759, Northern Nogova"
If leader1 is the player, then that could be the problem. Find another object-vehicle-unit to have the camera start off aiming at. Or have the camera aim at a precise point on the map:
_cam camSetTarget [-41944.58,94488.82,87.04]
If leader1 is not the player, then maybe it is the camsetrelpos command.
Instead of using:
_cam camsetrelpos [0,10,0]
use a precise point that you choose:
_cam camSetPos [2811.27,5063.36,1.03]
I do it that way (camsetpos and camsettarget) and I have never had a problem with it showing the player.
There is no way that I could come up with the coordinates like I stated above without using the camera.sqs method I learned here at OFPEC.
I beleive it is in the tutorial section by snYpir/messiah.
Basically you float the camera around to where you want and hit the ctrl button (or whatever is "fire" for your keyboard) and it takes a snapshot ('copy's it) of where the camera exaclty is and which way it is pointing --even vertical angles. Then you alt/tab out and paste the info into your intro script.
Don't know if that is what you were asking or if i'm telling you what you already know.
have a good one ;D