ATPL General Navigation - Class 7: Chart Types.

Summary

In this informative video, Grant introduces viewers to the fundamentals of chart design used in aviation, distinguishing charts from maps by their inclusion of specific navigational details such as airspace boundaries and navaids. The concept of projection is explored, explaining how 3D globe surfaces are represented on 2D displays with varying degrees of distortion. Grant discusses the importance of a right-angled graticule for accurate bearing and angle measurements, and the challenges of maintaining a constant scale for distance measurements. He outlines different types of projections, including cylindrical, conic, and azimuthal plane projections, each with their own benefits and compromises for navigation. The video concludes with advice on familiarizing oneself with chart symbology through resources like skyvector.com, emphasizing the need for an ideal chart to display accurate latitude and longitude, angles, distances, and terrain.

Takeaways

• 🌏 A chart is different from a map in that it displays information relevant to a specific use, such as airspace boundaries, airways, navaids, and airports for aviation.
• 📐 The concept of projection is fundamental to chart design, as it involves representing a 3D globe on a 2D display, which inevitably leads to some distortion.
• 🔍 Projections are chosen based on the elements desired in a chart, such as latitude and longitude, the ability to measure bearings and distances, and identifying high terrain.
• 🧭 A right-angled graticule is important for charts to display 90-degree intersections between latitude and longitude lines, aiding in accurate bearing and angle measurements.
• 📏 A fully conformal chart would have no distortion in scale or angles, but no such chart exists that achieves this across its entire size.
• 📦 Cylindrical projections, like the Mercator chart, wrap a piece of paper around the globe and trace the land's outline, which has some ideal properties but also compromises.
• 🎯 Conic projections place a cone over the globe, creating a fan-shaped projection with a small circle of tangency that serves as a parallel of latitude.
• 📈 Lambert's Conical Conformal chart is a well-known conic projection that attempts to minimize distortion for navigational purposes.
• 🌐 Azimuthal plane projections project the globe onto a flat surface touching at a single point, often used in polar stereographic charts.
• 📚 To understand chart symbology, it's recommended to explore websites like skyvector.com and familiarize oneself with various chart symbols.
• 🛫 The ideal chart would display accurate latitude and longitude, angles, distances, have a constant scale, identify high terrain, and show great circles or rhumb lines as straight, though no single projection can achieve this without some distortion.

Q & A

What is the primary difference between a map and a chart in the context of aviation?

A map is a visual representation of physical objects on Earth like forests, rivers, mountains, and coastlines. A chart, on the other hand, displays additional information relevant to its specific use, such as airspace boundaries, airways, navaids, and airports in aviation.

What is the fundamental concept of chart design known as projection, and why is it necessary?

Projection is the process of representing a 3D object, like the Earth's surface, on a 2D display such as paper or a flat screen. It is necessary because charts need to depict the 3D world on a flat surface for practical use in navigation and orientation.

How does the concept of projection lead to distortion on charts?

Projection leads to distortion because it involves transferring information from a 3D globe to a 2D surface. This transition cannot be done without altering the true shape and size to some extent, resulting in some form of distortion.

What are the key elements that aviation charts should display for effective navigation?

Aviation charts should display latitude and longitude, allow for the measurement of bearings and distances, identify high terrain, show great circles or rhumb lines as straight lines, and display appropriate information such as airspace boundaries and navaids.

Why is it important for the lines of latitude and longitude to intersect at 90-degree angles on a chart?

Intersecting latitude and longitude lines at 90-degree angles, known as a right-angled graticule, is important for accurate measurement of bearings and angles, which is essential for navigation.

What is a fully conformal chart, and why is it ideal for navigation?

A fully conformal chart is one where the scale and angles are not distorted in the projection. It is ideal for navigation because it allows for accurate representation of shapes and angles, which is crucial for measuring distances and bearings correctly.

Can you describe how a cylindrical projection is created for an aviation chart?

A cylindrical projection is created by imagining a piece of paper wrapped around the globe and then tracing the outline of the land onto the paper. The paper is then unwrapped and folded into a rectangle to create the chart. The point where the cylinder touches the globe is known as the great circle of tangency.

What is a Lambert's conical conformal chart, and how does it differ from a cylindrical projection?

A Lambert's conical conformal chart is a type of conic projection where a cone is placed over the globe, and the top of the cone is either above the North Pole or below the South Pole. The point of contact forms a small circle of tangency, which is also a parallel of latitude. Unlike cylindrical projections, conic projections focus on minimizing distortion over a specific area by adjusting the cone's steepness and point of tangency.

What is an azimuthal plane projection, and how does it differ from other types of projections?

An azimuthal plane projection involves placing a flat surface next to the globe and touching at a single point, usually one of the poles. The globe is then projected onto this flat surface. This type of projection differs from others as it focuses the projection on a single point, making it suitable for polar regions.

How can someone familiarize themselves with aviation chart symbols and their meanings?

To familiarize oneself with aviation chart symbols, one can visit websites like skyvector.com, enter a local or known airport, and explore the charts. By doing so, one can gradually build up knowledge of what various symbols represent, such as man-made buildings, runway symbols, and navigation beacons.