Airport data used in the AOPA Airport Directory comes from various sources. The two most common are the FAA and the Airport Manager. These sources are denoted by either an FAA badge or an AM badge next to the data element (see screenshot below). In the case of the pattern altitude at KMGR, the 1,100' MSL is what the airport manager (AM) reported and entered into the data. This value did not originate from AOPA or the FAA. If this is incorrect, the airport manager can contact us to have it updated.
The 1100 is msl and the 1000 in the Chart Supplement is agl, but that does not answer the question. 1300 would be the msl altitude to be flown since KGMR's elevation is 294 feet. So why does AOPA's airport information show a pattern altitude of 800 feet, agl?
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