3.4 Map Work & Locating Features

Introduction

Navigation is what a pilot does when flying cross-country. The act of navigation allows the pilot to know where they are at all times, thereby avoiding airspace in which they are not allowed to fly and taking the correct actions in airspace where they are allowed to fly.

Pilotage is navigation by reference to landmarks only, and those landmarks are shown on the VNC. Being able to use a VNC to navigate is therefore tested on the HAGAR examination.

Pilots must be able to execute several tasks on a VNC chart for the HAGAR examination. Many of these are straightforward and not worth detailed discussion here. Some non-trivial topics have already been discussed in previous sections. In this lesson, we focus on what remains.

VNC Task Summary

Task	How to
Identifying the location of a feature on the chart knowing the latitude and longitude of the feature	See Section 3.8
Specifying the latitude and longitude of a feature on the chart	See Section 3.8
Recognizing the various symbols on the map	Trivial. Look at the legend.
Identifying the altitude for each point on the chart	Trivial. Look at the legend. Depending on what is asked, use the elevation associated with the shading or the actual elevation of the feature shown on the map.
Recognizing isogonic lines	See Section 3.9
Identifying the magnetic deviation for each isogonic line on the chart	See Section 3.9
Knowing how to set a compass to read true north for a point on the chart	See Section 3.9
Identifying the airspace in which a particular point lies	See Section 2
Identify airways, air routes, control areas, control area extensions, transition areas, TCA, aerodrome traffic zones and control zones and the airspace in which they are located	See Section 2
Recognizing the altitude floor and ceiling for various airspace areas	See Section 2
Determining obstacles along a given cross-country route between specified points	See Section 4.4
Calculating the distance between two points on the chart in nautical miles, statute miles or kilometers	Trivial. Use a ruler to measure the distance between the two points and use the appropriate scale at the bottom of the VNC to determine the actual distance in the proper unit.
Converting distances between nautical miles, statute miles and kilometers	Trivial. Use a ruler and the scale at the bottom of the map.
Identify the tower frequency for various aerodromes	Trivial. Look at the legend to see where the information is shown and read it on the map.

Locating a Feature on a VNC

Any point on Earth can be located by intersecting circles called parallels of latitude and meridians of longitude. These are geographical coordinates.

• Longitude: Measured from 0° to 180° east and west of the Prime Meridian (through Greenwich, England). The Prime Meridian is numbered 0°. The meridian opposite is the International Date Line.
• Latitude: Measured from 0° to 180° north and south of the Equator. The Equator is at 0°.

On a VNC, longitude and latitude are measured in degrees, minutes, and tenths of minutes. There are 60 minutes in a degree.

For example: N46°15.6’ W77°30.9’ means 46 degrees 15.6 minutes north of the Equator and 77 degrees 30.9 minutes west of the Prime Meridian.

Note

Other systems use degrees, minutes, and seconds (60 seconds in a minute). Do not confuse this with the VNC convention of tenths of minutes.

On a VNC, parallels and meridians are represented by solid lines separated by 30’ (half a degree). The smallest graduation on these lines is one minute, so a tenth of a minute is very small on a VNC chart.

In the image below, you can practice identifying coordinates from a VNC excerpt and checking nearby map features.

Note

In a typical coordinate-identification question, read latitude first (N/S) and longitude second (E/W), then confirm the minute/tenth graduations carefully before finalizing your answer.