Session IV Measuring Latitude and Longitude

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

LAT/LON Expressions On a Nautical Chart: 042 deg 56 min 45 sec North 072 deg 45 min 25 sec West Typical GPS or LORAN read out: 042 56.750 N 072 45.417 W

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.

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

The LATITUDE SCALE on a Small Scale Chart usually depicts decimal minutes. The parallel line from the Bell. 11.0 min. Seconds or Tenths 041 10.7’ N 041 10’ 42” N 10.5 min Degrees 10.0 min. Minutes

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

Sixty Seconds of Latitude equals One Nautical Mile DISTANCE Sixty Seconds of Latitude equals One Nautical Mile

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

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

The vertical line from the Bell. The Longitude Scale The vertical line from the Bell. Seconds or Tenths Degrees Minutes 071 01.4’ W or 071 01’ 24” W

END OF Session IV