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development of the Lambert conformal conic projection is shown by Figure 1.29.
Figure 1.29. Lambert Conformal Conic Projection.
46 AFPAM11-216 1 MARCH 2001
1.26.2. Uses. The chief use of the Lambert conformal conic projection is in mapping areas of small
latitudinal width but great longitudinal extent. No projection can be both conformal and equal area but,
by limiting latitudinal width, scale error is decreased to the extent the projection gives very nearly an
equal area representation in addition to the inherent quality of conformality. This makes the projection
very useful for aeronautical charts.
1.26.3. Advantages. Some of the chief advantages of the Lambert conformal conic projection are:
1.26.3.1. Conformality.
1.26.3.2. Great circles are approximated by straight lines (actually concave toward the midparallel).
1.26.3.3. For areas of small latitudinal width, scale is nearly constant. For example, the United States
may be mapped with standard parallels at 33o N and 45o N with a scale error of only 2 percent for
southern Florida. The maximum scale error between 30o30' N and 47o30' N is only one-half of 1 percent.
1.26.3.4. Positions are easily plotted and read in terms of latitude and longitude. Construction is
relatively simple.
1.26.3.5. Its two standard parallels give it two lines of strength (lines along which elements are
represented true to shape and scale).
1.26.3.6. Distance may be measured quite accurately. For example, the distance from Pittsburgh to
Istanbul is 5,277 NM; distance as measured by the graphic scale on a Lambert projection (standard
parallels 36o N and 54o N) without application of the scale factor is 5,258 NM; an error of less than fourtenths
of 1 percent.
1.26.4. Limitations. Some of the chief limitations of the Lambert Conformal conic projection are:
1.26.4.1. Rhumb lines are curved lines which cannot be plotted accurately.
1.26.4.2. Maximum scale increases as latitudinal width increases.
1.26.4.3. Parallels are curved lines (arcs of concentric circles).
1.26.4.4. Continuity of conformality ceases at the junction of two bands, even though each is conformal.
If both have the same scale along their standard parallels, the common parallel (junction) will have a
different radius for each band and will not join perfectly.
1.26.5. Constant of the Cone. Most conic charts have the constant of the cone (convergence factor)
computed and listed on the chart somewhere in the chart margin.
1.26.6. Convergence Angle (CA). The CA is the actual angle on a chart formed by the intersection of
the Greenwich meridian and another meridian; the pole serves as the vertex of the angle. CAs, like
longitudes, are measured east and west from the Greenwich meridian.
AFPAM11-216 1 MARCH 2001 47
1.26.7. Convergence Factor (CF). A chart's CF is a decimal number which expresses the ratio between
meridional convergence as it actually exists on the earth and as it is portrayed on the chart. When the
convergence angle (CA) equals the number of the selected meridian, the chart CF is 1.0. When the CA is
less than the number of the selected meridian, the chart CF is proportionately less than 1.0.
1.26.7.1. The subpolar projection illustrated in Figure 1.30 portrays the standard parallels, 37o N and 65o
N. It presents 360o of the earth's surface on 282.726o of paper. Therefore, the chart has a CF of 0.78535
(282.726o divided by 360o equals 0.78535). Meridian 90o W forms a west CA of 71o with the Greenwich
meridian.
1.26.7.2. Express as a formula:
CF X longitude = CA
0.78535 X 90o W = 71o west CA
1.26.7.3. Approximate a chart's CF on subpolar charts by drawing a straight line covering 10 lines of
longitude and measuring the true course at each end of the line, noting the difference between them, and
dividing the difference by 10. NOTE: The quotient represents the chart's CF.
Figure 1.30. A Lambert Conformal, Convergence Factor 0.78535.
Section 1G— Aeronautical Charts
1.27. Basics. An aeronautical chart is a pictorial representation of a portion of the earth's surface upon
which lines and symbols in a variety of colors represent features or details seen on the earth's surface. In
addition to ground image, many additional symbols and notes are added to indicate navigational aids
(NAVAID) and data necessary for air navigation. Properly used, a chart is a vital adjunct to navigation;
improperly used, it may become a hazard. Without it, modern navigation would never have reached its
48 AFPAM11-216 1 MARCH 2001
present state of development. Because of their great importance, the navigator must be thoroughly
familiar with the wide variety of aeronautical charts and understand their many uses.
1.27.1. Lambert Conformal. Aeronautical charts are produced on many different types of projections.
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