Mike Rapoport wrote:
Recently the COE VOR was notamed OTS. Coincedent with this the KSZT LOC/DME
was notamed NA. The explanation given was that the COE VOR was nessasary to
fly the tranition (COE is the IAF) and the missed approach (the missed ends
with a hold at the COE VOR). I contend that GPS can substitute for the VOR
but I can't find it witten down anywhere. The KSZT LOC, DME and ADF are all
working properly. Our question is: Was the KSZT LOC/DME approach
improperly NOTAMed NA? Can you cite a source? Remember we are talking
about substituting GPS for the VOR to fly the transition, we are not talking
about substituting for the LOC.

Mike,
Google "FAA, sole source navigation, GPS"
There are many articles out there.
From what I skimmed, we are still in transition to becoming sole source.
Sole source is dependent upon other parts such as WAAS and LAAS becoming
accepted as operational.