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They represent the direction to True North. At the equator, one minute of arc longitude equals one nautical mile.
The only place where 1° longitude = 1 Nm is on the equator. As one moves toward either pole, the lateral distance
across one degree becomes less and less, and approaches zero at the pole. Since the earth makes one revolution of
360 degrees within 24 hours, it moves 15° in one hour.
The lines running around the earth, parallel to the equator, are called lines of parallel (or parallels). They are
measured from the equator to the poles in terms called degrees of latitude. They range from 0° latitude at the
equator to 90° latitude at the poles. They are termed North latitude in the Northern Hemisphere, and South
latitude in the Southern Hemisphere. Unlike Meridian Lines, lines of parallel are equidistant between them (since
they are parallel and do not converge). One minute of latitude equals a nautical mile.
The Latitude of the dot shown on the earth’s surface in the diagram above is defined as 35° 20’ N. Therefore, the
location of the dot can be explicitly defined as 35° 20’N - 30° 45’ W.
Aeronautical charts show horizontal latitude lines and vertical longitude lines at 30 minute intervals. They are
labeled near the edges of the chart, and periodically along the line. There are 30 “tick” marks between each 30
minute line, each representing one minute. The 10 minute marks are long, and the 5 minute marks are
intermediate in length. One can determine latitude by locating the line below the point in question, then count
upward, adding the number of tick marks from the reference line. When parallel with the point, the latitude
location has been reached. (NOTE: If the latitude line is above the point in question, count the tick marks
downward. Subtract them from the latitude line value. When moving North, add degrees and minutes. When
moving South, subtract degrees and minutes).
To find the longitude of a point is similar. Count the tick marks either East or West from the reference longitude
line to the point in question. When going in a westerly direction, add degrees and minutes. Subtract degrees and
minutes when going in an easterly direction. (Note: these rules apply only in the North and Western Hemisphere.)
Three airport locations are shown below. Listed below are their ID, Latitude and Longitude. The diagram shows
how to find the location of each airport. (Note: These points are shown on the Charlotte Sectional Aeronautical
Chart).
Chart Symbols
http://www.uncletom2000.com/gs/chartsym.htm (2 of 9) [1/23/2003 11:19:04 AM]
SVH 35° 46’ N 80° 57’ W
LEX 35° 47 N 80° 18’ W
3N8 35° 23’ N 80° 42’ W
Note: The 36 degree North Latitude line simply has the number 36° on it at the left end of the line.
The line below it has 30’ on it. Although the number 35° does not occur on the chart, the line is 35° 30’ by
inference. Charts such as this can occur on the Private Pilot Written Exam, so learn how to interpret the degree
and minute legends on the charts.
To find the Lat/Lon of SVH, project a line both vertically and horizontally from the center of the airport (follow
the blue dotted lines). Go to the 81° Longitude line, and count horizontally eastward by 3 minutes (3 tick marks
east). When counting a number of tick marks toward the East, treat the count as a negative value. This yields a
latitude = 81° 0’ - 0° 03’ = 80° 57’ W.
Likewise, go to the 35° 30’ Latitude line. Count upward 0° 16’ (16 tick marks). When counting northward, the
count of the tick marks is positive) The Latitude of the airport is therefore 35° 30’ + 0°16 ‘ = 35° 46’ N. You
could also have gone up to the 36° 00’ line and counted downward 14 minutes to also get a 46’ point north of
Latitude 35°. In this case, you would have counted toward the South, so that the count of tick marks is negative.
In the US, when you encounter a line marked 30’ (30 minute), you must go to the next Lower Latitude Line to
determine the degrees. Similarly, when a longitude line has only a 30’ (30 minute ) label, you will have to go to
Chart Symbols
http://www.uncletom2000.com/gs/chartsym.htm (3 of 9) [1/23/2003 11:19:04 AM]
the right (eastward) to the next line to determine the degree of Longitude.
Time Zones
The United States lies between 67°W and 125° W.
This spans 4 time zones. Meridians are useful in
determining time zones. When the sun is directly
above a meridian, it is noon at that meridian. To the
West of that meridian, it is forenoon; to the East, it is
　
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