Aeronautical Charts Explanation of VFR Terms and Symbols

The discussions and examples in this manual are based on the Sectional Aeronautical Chart (Sectionals). Sectionals include the most current data and are at a scale (1:500,000) most beneficial to pilots flying under, Visual Flight Rules. A pilot should have little difficulty in reading these charts, which are, in many respects, similar to automobile road maps. Each chart is named for a major city within its area of coverage.

The chart legend lists various aeronautical symbols as well as information concerning drainage, terrain and contour elevations. You may identify aeronautical, topographical, and obstruction symbols (such as radio and television towers) by referring to the legend. Many landmarks, which can be easily recognized from the air, such as stadiums, pumping stations, refineries, etc., are identified by brief descriptions adjacent to small black squares marking their exact locations. Oil wells are shown by small open circles. Water, oil and gas tanks are shown by small black circles and labeled accordingly, if known. The scale of an item may be increased to make it easier to read on the chart.

HYDROGRAPHY
Two tones of blue are used to distinguish water
areas identified as "Open Water" and "Inland Water".
Open Water is defined as the limits (shorelines)
of all coastal features at mean high water for
oceans, seas and associated waters such as bays,
gulfs, sounds, fords, large estuaries, etc.
Exceptionally large lakes such as the Great Lakes,
Great Bear Lake, Great Slave Lake, etc., will be
considered as Open Water features. The Open
Water tone will be extended inland as far as
deemed necessary to adjoin the Inland Water tone
(generally where drainage lines coalesce to a width
of 0.1" approximate).

Inland Water is defined as all
other bodies of water. Cartographic judgment is used as
required in some instances.

TERRAIN AND OBSTRUCTIONS
The elevation and configuration of the Earth's
surface is certainly of prime importance to pilots. Cartographers devote a great deal of attention to
showing relief and obstruction data in a clear and
concise manner. Five different techniques are used:
contour lines, shaded relief, color tints, obstruction
symbols, and Maximum Elevation Figures (MEF).

1. Contour lines are lines
connecting points on the Earth
of equal elevation. On
Sectionals, basic contours are

spaced at 500' intervals. Intermediate
contours may also be shown at 250' intervals in
moderately level or gently rolling areas. Occasionally, auxiliary contours at 50, 100, 125, or
150' intervals may be used to portray smaller relief
features in areas of relatively low relief. The pattern
of these lines and their spacing gives the pilot
visual concept of the terrain. Widely spaced contours
represent gentle slopes, while closely spaced
contours represent steep slopes.

2. Shaded relief is a
depiction of how the
terrain might appear from
the air. The cartographer
shades the areas that
would appear in shadow if
illuminated by a light from
the northwest.

Studies have indicated that our visual perception has been
conditioned to this view.

3. Color tints, also referred to as hypsometric
tints, are used to depict bands of elevation
relative to sea level. These colors range
from light green for the lowest elevations to
dark brown for the higher elevations.

4. Obstruction symbols are used to
depict man-made vertical features that may
affect the National Airspace System. Aero-
Nav Services maintains a database of nearly
127,000 obstacles in the United States,
Canada, the Caribbean and Mexico. Each
obstacle is evaluated by cartographers
based on charting specifications before it is
added to visual charts. When the position
or elevation of an obstacle is unverified, it is
marked UC (under construction or reported
but not verified).

Aeronautical Charts Terms and Symbols VFR Aeronautical Charts Explanation of VFR Terms and Symbols

Aeronautical Charts Terms and Symbols
VFR Aeronautical Charts
Explanation of VFR Terms and Symbols