LOW-LEVEL AND TACTICAL FORMATION
Figure C-3 Contour Lines
Spot Elevations. Spot elevations are the heights of particular points of terrain above an
established datum plane, usually at sea level. Spot elevations are identified on the ONC, TPC,
and JOG. Accuracy to within 100 feet is indicated by black numbers preceded by a dot, which
indicates the exact location of the elevation (.000). Approximate elevations are shown in black
numbers preceded by a small x (x0000). Undetermined locations are indicated by omission of
the point locator (0000). Critical elevations (mountain peaks) are indicated by heavy black
numbers and dots (.0000).
Maximum Elevation Figure (MEF). The MEF is based on the highest point, natural or
man-made, within a given grid square (Figure C-4). The MEF is determined by adding a 200-
foot safety margin, plus a vertical accuracy factor, to the highest point in the grid square, and
then rounding up to the next 100-foot increment. If you fly at the MEF, you should have at least
200 feet of obstruction clearance.
Cultural Features. All man-made structures appearing on a chart are called cultural
features. The following three factors govern the amount of detail: the scale of the chart, use of
the chart, and geographical area covered. Population centers, roads, railroads, towers, power
lines, dams, and bridges are some of the many kinds of cultural features portrayed on
aeronautical charts. The true representative size and shape of larger cities and towns are shown.
Standardized coded symbols and type sizes are used to represent the smaller population centers.
Although most symbols denoting cultural features are keyed in the legend, some are self-
explanatory. Examine cultural features with caution; if the chart is several years old, man-made
features have certainly changed.
NAVIGATIONAL CHARTS C-5