Overview
This lecture explains the concepts of latitude and longitude, how to interpret geographic coordinates, and how to use them to locate positions, especially on VFR sectional charts for pilot exams.
Latitude and Longitude Basics
- Latitude and longitude are imaginary lines that help identify positions on the globe.
- Latitude lines run parallel to the equator, starting at 0° (equator) to 90° north or south (poles).
- The equator divides the globe into northern and southern hemispheres.
- Longitude lines run perpendicular to the equator, from 0° (Prime Meridian at Greenwich) to 180° (International Date Line).
- Western longitudes are labeled "W" and increase as you travel west; eastern longitudes do the opposite.
Units of Measurement
- Each degree of latitude or longitude is divided into 60 minutes ('), and each minute is divided into 60 seconds (").
- One minute of latitude or longitude equals one nautical mile.
- Minutes and seconds breakdown follows the 60:1 rule used in aviation calculations.
Writing and Calculating Coordinates
- Coordinates are written with hemisphere (N, S, E, W), degrees, minutes, and seconds (e.g., N32°21'12").
- To calculate distance from the equator or prime meridian: multiply degrees by 60, add minutes, and convert seconds (seconds/60).
- Example: N32°42'12" = (32×60) + 42 + (12/60) = 1962.2 nautical miles from the equator.
Using VFR Sectionals for Coordinates
- VFR sectional charts mark latitude and longitude in degrees and 30-minute increments, with hash marks for individual minutes.
- To determine an exact location: identify the nearest degree, count the minutes, and, if needed, estimate the seconds.
- Example: Libby Airport is at N48°17', W115°29' based on sectional tick marks.
Finding Locations from Given Coordinates
- To find what is at a set of coordinates, locate the correct degree, minutes, and seconds on the chart, then identify the nearest feature (e.g., airport or town).
- Example: Coordinates N46°57'24", W112°44'45" correspond to Cane Ranch airport.
Key Terms & Definitions
- Latitude — Parallel lines indicating distance north or south of the equator.
- Longitude — Perpendicular lines showing distance east or west of the Prime Meridian.
- Nautical Mile — A unit equal to one minute of latitude.
- VFR Sectional — A map used by pilots showing geographic and airspace information, with latitude and longitude lines.
Action Items / Next Steps
- Review how to identify and write latitude and longitude coordinates.
- Practice reading locations and coordinates on VFR sectional charts.
- Prepare for FAA written questions involving geographic coordinates.