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course line on the chart will then be aligned with the intended course of the aircraft so that landmarks on
the ground appear in the same relative position as the features on the chart. Obtain the approximate
position of the aircraft by DR. Select an identifiable landmark on the chart at or near the DR position. It
is important to work from the chart to the ground. Identify the landmark selected and fix the position of
the aircraft. The importance of a good DR cannot be over emphasized. When there is any uncertainty of
position, every possible detail should be checked before identifying a checkpoint. The relative positions
of roads, railroads, airfields, and bridges make good checkpoints. Intersections and bends in roads,
railroads, and rivers are equally good. When a landmark is a large feature, such as a major metropolitan
area, select a small prominent checkpoint within the large landmark to fix the position of the aircraft.
170 AFPAM11-216 1 MARCH 2001
When a landmark is not available as a reference at a scheduled turning point, make the turn on the
estimated time of arrival (ETA). Extend the DR position to the next landmark and fix the position of the
aircraft to make sure the desired course and GS are being maintained. Remember, the desired magnetic
course on any given leg corrected for drift is the magnetic heading which will parallel course. This will
help to keep from getting any farther off course.
6.5. Low-Level Map Reading. On low-level flights, you may encounter additional difficulties.
Turbulence increases the difficulty of reading instruments. Depending on the aircraft's altitude above
ground level (AGL), the circle of visibility can be greatly reduced, and those objects that are visible pass
by so rapidly only the largest landmarks can be easily identified.
6.5.1. In low-level navigation, flight planning is especially important as there is little time for in flight
computations. An important part of good mission planning is proper chart preparation. The most
commonly used chart for low-level day operations is the JOG chart and at night a TPC. Normally radiusof-
turn procedures are used when drawing the chart, but depending on your tactics point to point is also
an option. Time elapsed marks and distance remaining marks along the course line of each leg will give
navigators a running DR with the aid of a stopwatch.
6.5.2. In low-level flight, one should be particularly alert to possible danger from obstructions. Hills and
mountains are easily avoided if the visibility is good. Radio and television towers, which may extend as
much as 1,000 feet or more into the air, often from elevated ground, are less conspicuous. All such
obstructions may or may not be shown on the aeronautical charts. Keep your charts updated with the
location of new obstructions by using the Chart Updating Manual (CHUM). The CHUM lists important
changes to all current navigation charts, but does not contain manmade obstacles less than 200 feet tall.
The CHUM is published twice a year with supplements published monthly. Electronic updates are also
available.
6.6. Map Reading at Night. At night, unlighted landmarks may be difficult or impossible to see. Lights
can be confusing because they appear closer than they really are. Fixing on points other than those
directly beneath the aircraft is very difficult. Objects may be more easily seen by scanning or looking at
them indirectly to eliminate the eye's visual blindspot. Preserve your night vision by working with red or
green light, being aware that red light can detract from the chart color. Moonlight makes it possible to
see prominent landmarks like land-water contrast. Reflected moonlight often causes a river or lake to
stand out brightly for a moment, but this condition is usually too brief for accurate fixing. Roads and
railroads may be seen after the eyes are accustomed to the darkness. Lighted landmarks, such as cities
and towns, stand out more clearly at night than in daytime. Large cities can often be recognized by their
distinctive shapes. Many small towns are dark at night and are not visible to the unaided eye. Night
vision goggles dramatically enhance map reading in dark areas. Some airfields have distinctive light
patterns and may be used as checkpoints. Military fields use a double white and single green rotating
beacon, while civilian fields use a single white and single green rotating beacon. Busy highways are
discernible because of automobile headlights.
6.7. Estimating Distance. A landmark often falls right or left of course and the navigator must estimate
the distance to it. While the ability to estimate distance from a landmark rests largely in skill and
experience, the following methods may be of assistance. One method is to compare the distance to a
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