Gps moca ?

[c310flyr]

If this has been asked, I have missed this.

T routes for gps often show an mea but also a starred altitude as a moca

I know if it was for a vor, it would be for within 22 miles of the station

For gps it makes no sense.

I think it might guarantee comm, but can find no reference in the aim

Anyone know for sure ?
Thanks

 

[midlifeflyer]

Check the discussion of MOCA in the IPH.

Ultimately, although the MOCA does guarantee VOR reception within 22 nm, it's main purpose is obstruction clearance.

OTOH, although MEA is technically defined in terms of its guarantee of obstruction and nav signals, their actual establishment includes such factors as airspace, air traffic flow and communications capability. You can really see this at work on some SID and STAR charts where the "MEA" for a route is thousands of feet higher than the "MEA" for the exact same route on the enroute chart.

 

[flyingron]

Signal coverage for a GPS isn't going to be much affected by altitudes if you're not low enough for obstructions to be an issue.

Don't forget that communications requirements also fit into MEA determination.

MOCA, as Mark says, is purely determined by obstacles on the route (in this case) or in the area when you're talking GPS routes.

 

[aterpster]

Signal coverage for a GPS isn't going to be much affected by altitudes if you're not low enough for obstructions to be an issue.

You're seldom low enough for terrain to adversely affect GPS unless you are in a narrow box canyon. You may lose some sats down low in a place such as the Owens Valley, but not to the extent that constellation geometry is compromised.

 

[flyingron]

You're seldom low enough for terrain to adversely affect GPS unless you are in a narrow box canyon. You may lose some sats down low in a place such as the Owens Valley, but not to the extent that constellation geometry is compromised.

That was meant to be kind of tongue-in-cheek.