Coastal Navigation Using GPS

1
Session IV Measuring
Latitude and Longitude
2
General Rules

• On a chart, LAT/LON is read in
• Degrees
• Minutes
• Seconds or Tenths 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 Tenths 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
3
Step FOUR - Read the seconds or tenths of
latitude.
1
4
5
The LATITUDE SCALE on a Small Scale Chart usually depicts decimal minutes.
11.0 min.
Seconds or Tenths
10.5 min
041 10 42 N
Degrees
10.0 min.
Minutes
6
DISTANCE
One Minute of Latitude equals One Nautical Mile
7
The Second Scale on a Small Scale Chart
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.
1
3
Step FOUR - Read the seconds or tenths of Longitude.
4
9
The Longitude Scale
The vertical line from the Bell.
Seconds or Tenths
Degrees
Minutes
071 01.4 W or 071 01 24 W
10
END OF Session IV