FANR5640/7640: Sectionals – Lat/Lon

Latitude/Longitude Review 

Please refer to the graphic below:

Latitude refers to the lines that run horizontally, parallel to the Equator.  When one moves to the next line of latitude they travel in a north-south direction, they are traveling “up the ladder”.  In Cartesian space such as our sectional maps, latitude is a measurement along the Y-axis.  Latitude increases as you move north and decreases as you move south and is always positive here in the northern hemisphere.  Latitude values range from 90° at the North Pole to -90° at the South Pole.  When using DMS, the labels “N” and “S” are used to identify a point in the northern or southern hemisphere instead of a “-” (or the absence of a “-“).


Longitude refers to the lines that run “long-ways” through the north and south pole.  When one moves to the next line of longitude they travel in an east-west direction.  In Cartesian space such as our sectional maps, longitude is a measurement along the X-axis. Longitude increases as you move west and decreases as you move east and is always negative here in the western hemisphere.  Longitude values range from -180° to 180° with the origin running through the Royal Observatory in Greenwich, England.  Labels “W” and “E” are used to note if the point is in the western hemisphere or the eastern hemisphere when presenting the coordinate in DMS format (instead of “-” or the absence of “-“).
The unit of measure for lat/long is the degree and it is typically shown in degree/minute/second (DMS) format (D°M’S”N, D°M’S”W).
The key concept of DMS you need to understand is that:
  • there are 60 seconds in one minute,
  • there are 60 minutes in one degree, and with a little math we can show that
  • there are 3,600 seconds in 1 degree.

When you report a coordinate pair using DMS, you must reduce the seconds and you must reduce the minutes.  In other words, your second and minute measures should always be less than 60.

Gold Seal Flight Training’s Sectional Charts: Latitude and Longitude

Consider the sectional below, what is the lat/long coordinate of the Santa Catalina airport (to the nearest degree/minute)?

  • locate the airport
  • extend a line to the nearest labeled line of longitude
    • add if you move west, subtract if you move east
  • extend a line to the nearest labeled line of latitude
    • add if you move north, subtract if you move south

The answer is 33º24’N, 118º25’W

RP101, L6.6

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