The Pilot Controller Glossary (and other places) define MOCAs as:
MINIMUM OBSTRUCTION CLEARANCE ALTITUDE (MOCA)− The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments which meets obstacle clearance requirements for the entire route segment and which assures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.
VORs aren’t used in GPS navigation so I don’t understand why there would be a GPS MOCA on a T-Route or Victor Airway.
Even the example given in the Aeronautical Chart Users Guide (p56) has a GPS MOCA below the MEA.
I would think the GPS MEA would be the MOCA or even lower, since VOR reception isn’t required in the first 22 miles. If you fly at the MEA it guarantees that a normal climb will keep you above obstacles when entering the next segment with a higher MEA. But I would think that the MOCA would do the same thing unless there was an MCA. So that doesn’t seem to be a reason.
There are even T-Routes in Florida with a GPS altitude and a lower GPS MOCA. That makes even less sense to me.
Does the GPS MOCA also take into account communication reception—but in that case why isn’t that mentioned in the regular MOCA definition?
If anyone could shed some light on how they come up the GPS MOCAs it would be appreciated.