Primary target: An aircraft not reporting mode-C, the only thing the controller has is the return on the radar.
When a controller reports a primary target as traffic to other aircraft, the controller does not have the altitude of the target. Given this, I conclude that ATC radar does not have the altitude (angle-up) to the target, and only provides azimuth.
So then without the altitude, how does the radar-system know where to put the target laterally on the screen?
Example, a radar picks up a target that is 10 miles from the station. If the target is 0 AGL, the proper position would be 10 miles out. However, if the target is at 15,000ft, the proper position would be 9.5 miles out.
Since the difference is so small, does the radar just put the target at 10 miles, and the FAA separation guidelines factor in the discrepancy?