4. Round the figure up to the next higher hundred
foot level.

Example: Elevation of obstacle top (MSL) = 3450
Possible vertical error +100
Obstacle Allowance +200
equals 3750
Raise to the following 100' level 3800
Maximum Elevation Figure

Pilots should be aware that while the MEF is
based on the best information available to the cartographer,
the figures are not verified by field surveys.
Also, users should consult the Aeronautical Chart
Bulletin in the A/FD or AeroNav Services website to
ensure that your chart has the latest MEF data available.

RADIO AIDS TO NAVIGATION
On visual charts, information about radio aids
to navigation is boxed, as illustrated. Duplication of
data is avoided. When two or more radio aids in a
general area have the same name with different
frequencies, TACAN channel numbers, or identification
letters, and no misinterpretation can result, the name
of the radio aid may be indicated only once within the
identification box. VHF/UHF radio aids to navigation
names and identification boxes (shown in blue) take
precedence. Only those items that differ (e.g., frequency,
Morse Code) are repeated in the box in the
appropriate color. The choice of separate or combined
boxes is made in each case on the basis of economy
of space and clear identification of the radio aids.

Radio aids to navigation located on an airport
depicted by the pattern symbol may not always be
shown by the appropriate symbol. A small open circle
indicates the NAVAID location when collocated with an
airport symbol. The type of radio aid to navigation will
be identified by: VORTAC, VOR or VOR-DME, positioned
on and breaking the top line of the NAVAID box.

AIRPORTS
Airports in the following categories are charted
as indicated (additional symbols are shown later in
this Section).

Public use airports:
Hard-surfaced runways greater than 8069' or
some multiple runways less than 8069'
Hard-surfaced runways 1500' to 8069'
Other than hard-surfaced runways
Seaplane bases

Military airports:
Other than hard-surfaced runways
Hard-surfaced runways are depicted the same
as public-use airports.
U.S. military airports are identified by abbreviations
such as AAF (Army Air Field), AFB (Air
Force Base), MCAS (Marine Corps Air Station),
NAS (Naval Air Station), NAF (Naval Air
Facility), NAAS Naval Auxiliary Air Station),
etc. Canadian military airports are identified by
the abbreviation DND (Department of National
Defense).

Services available:
Tick marks around the basic airport symbol indicate
that fuel is available and the airport is tended
during normal working hours. (Normal working hours
are Monday through Friday 10:00 A.M. to 4:00 P.M.
local time.)
Other airports with or without services: