NAV - Maps & Charts Flashcards
What are Maps & Charts commonly known as? (1)
Two-dimensional projection of the Earth’s surface
What do Charts show? (3)
- Lines of latitude and longitude
- Coastal outlines
- Normally used for plotting
What do Maps show? (2)
- Significant additional Topographical detail
- May be used for visual map reading
What is a Chart Scale? (2)
- The ratio between the chart distance and the Earth distance that it represents
- Shown in Fraction or Ratio or Statement in words
What are the differences in Small and Large Scale? (2)
- The larger the scale denominator, the greater the distance shown ∴ the less detail will be shown. = Small scale
- The smaller the scale denominator, the smaller the distance shown ∴ the more detail will be shown. = Large Scale
What should a Map project? (1)
Reproducing all features of the original sphere would be perfectly equidistant
e.g. distances between every two points would keep the same ratio on both map and sphere
How should a Map be conformal? (6)
- All angles and bearings on the Earth are accurately represented on the chart
- Scale distortion at any point must be the same in all directions
- Each parallel must cross every meridian at right angles
- Enables all directions, headings and bearings to be measured correctly
- Without this property the chart would be unsuitable for flight navigation
- “Conformal” will appear in the name of the chart
What is Azimuthal Stereographic used for? (3)
- Topographical and specialist aeronautical charts for polar regions
- Large area meteorological forecast charts
- It is conformal
What is a Mercator map?
- Accurately projects along the line of tangency where the cylinder touches the Earth
- The only conformal cylindrical projection
- In order to keep shapes undistorted, Antarctica is enormously stretched, and Greenland is rendered about nine times larger than actual size
What Lines are shown on a Mercator Map? (2)
- Rhumb Lines appear as straight lines
- Great Circles are projected as shallow curves concave to the Equator
What Line is used for a shortest route? (1)
The Great Circle line
What is the Lamberts Conformal Conic? (2)
- A cone instead of a cylinder with the paper touching the Earth at a Parallel of Latitude known as the Parallel of Origin
- Only a Lambert Conic is conformal
How is the Lamberts Conic modified? (1)
- Modified with 3 cones around the Earth
Modified projection of Lamberts Conic diagram (4)
- Scale correct where the cone touches the Earth
- Scale contracts within the two points
- Scale expands outside the two points
- A Lambert projection Chart may be considered to exhibit constant scale
How are Lines are shown on a Lamberts Conic, and what is it used for? (4)
- Great Circles appear as straight lines
- Rhumb Lines are projected as concave to the nearest Pole
Used for:
- Plotting radio bearings.
- Long distance flights using great circle tracks
