5. Maps And Charts Flashcards
What is Conformality?
The angle between any two lines on the sphere must be the same between their projected counterparts on the map; in particular, each parallel must cross every meridian at right angles
So, to be CONFORMAL…
- 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.
Types of conformal?
The Azimuthal Stereographic - Azimuthal (projections onto a plane)
Used to produce:
Topographical and specialist aeronautical charts for Polar regions & Large area meteorological
forecast charts.
What is a Mercator?
Accurately projected along the line of tangency where the cylinder touches the
Earth. The only conformal cylindrical projection, Mercator’s device was a boon to navigators from the
16th-century until the present, despite suffering from extreme area distortion near the poles:
What are Mercators used for?
Used to produce topographical charts of countries that extend for long distances northsouth but short distances east-west
e.g., New Zealand, Italy, United Kingdom,Chili and Argentina
Properties of a Mercator?
Rhumb Lines appear as straight lines
Great Circles are projected as shallow curves concave to the Equator
Any Mercator (or Azimuthal Stereographic) is conformal.
Lamberts Conformal Conic
The only conformal conic projection. A cone instead of a cylinder with the paper touching the Earth at a Parallel of Latitude known as the Parallel of Origin – all but one are non- conformal.
Properties of Lamberts Conformal Conic?
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. Great Circles appear as straight lines. Rhumb Lines are projected as concave to the nearest Pole .
What is lamberts conformal conic Used for?
- Plotting radio bearings
- Long distance flights using great circle tracks
Practical application using: UK 1:250,000 “Quarter Mill.” Chart.
A Mercator graticule is based on a projection that is?
A cylindrical projection
A Lambert conical projection is a conformal projection where?
a rhumb line appears as a straight line and distortion over the entire area is minimal.
The ratio between the chart distance and the earth distance that it represents is the?
Scale of the chart or map.
What is a GRATICULE?
a network of lines is established on a map or on the surface of the Earth by the
Prime Meridian, the meridians, the Equator and the parallels
