1. Session IV
Measuring
Latitude and Longitude

2. General Rules Set your GPS to read DEGREES – MINTUES - SECONDS
On a chart, LAT/LON is read in:
Degrees
Minutes
Seconds or Tenth’s of a Minute
Set your GPS to read
DEGREES – MINTUES - SECONDS

3. Rules for reading LAT/LON
On a Nautical Chart:
Read the Degrees from the LAT/LON scales.
Read the Minutes from the LAT/LON scales.
Measure the Seconds or Tenth’s of a Minute.

4. Measuring the Seconds of Latitude.
Step ONE – Place one point of the dividers on the object or target.
Step TWO - Stretch the other point of the dividers to nearest Parallel of Latitude.
Step THREE - Without disturbing the opening, move the dividers to the Latitude scale in the left or right margins. 2
Spread dividers and put one point on object
The nearest line is 41° 20’N
You want to insure it is just touching the line
Read off the longitude at the bottom
Answer 3
Step FOUR - Read the seconds or tenths of latitude. 4 1

5. The LATITUDE SCALE on a Small Scale Chart usually depicts decimal minutes.
Seconds or Tenths
’ N
041 10’ 42” N
10.5 min
Degrees
10.0 min.
Minutes

6. One Minute of Latitude equals One Nautical Mile
DISTANCE
One Minute of
Latitude
equals
One Nautical Mile

7. 6 seconds 1/10 of a Mile ONE NAUTICAL MILE
The Second Scale on a Small Scale Chart
6 seconds
1/10 of a Mile
SIXTY
SECONDS OF
LATITUDE
ONE
NAUTICAL
MILE

8. Measuring the Seconds of Longitude
Step ONE - Place one divider point on the object or target..
Step TWO - Stretch the other point of the dividers back to the nearest meridian of Longitude. 2
Step THREE - Without disturbing the opening, move the dividers to the Longitude Scale at the top or bottom margin.
Spread dividers and put one point on object
The nearest line is 071° 20’W
You want to insure it is just touching the line
Read off the longitude at the bottom
Answer 1 3
Step FOUR - Read the seconds or tenths of Longitude. 4

9. The vertical line from the Bell.
The Longitude Scale
The vertical line from the Bell.
Seconds or Tenths
Degrees
Minutes
’ W or ’ 24” W

10. END OF
Session IV