Sounds like APM (Approach Path Monitoring).
Our system has it (as well as DPM- Departure Path Monitoring) but not activated yet.
Basically 3-D polygons adapted that trigger an alert if the a/c strays laterally or vertically from the defined path.
Would have thought very difficult to adapt separate approach paths with such close spacing as SFO has, that didn’t set off nuisance alerts often.
Last edited by bekolblockage; 16th January 2018 at 01:32.