Gnomonic |
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Release 9.2
Last modified August 3, 2007 |
Print all topics in : "Supported map projections" |
This azimuthal projection uses the center of the earth as its perspective point. All great circles are straight lines, regardless of the aspect. This is a useful projection for navigation because great circles highlight routes with the shortest distance.
This is a planar perspective projection viewed from the center of the globe. The projection can be any aspect.
A single point anywhere on the globe.
Polar aspect—North Pole or South Pole.
Equatorial aspect—any point along the equator.
Oblique aspect—any other point.
All meridians and the equator.
Degrees from center (°) | Meridian distortion (%) | Latitude distortion (%) |
15.0 | 7.2 | 3.5 |
30.0 | 33.3 | 15.5 |
45.0 | 100.0 | 41.4 |
60.0 | 300.0 | 100.0 |
This projection is limited by its perspective point and cannot project a line that is 90° or more from the center point; this means that the equatorial aspect cannot project the poles, and the polar aspects cannot project the equator.
A radius of 30° produces moderate distortion, as indicated in the table above. This projection should not be used more than about 60° from the center.
All aspects—routes of navigation for sea and air.
Polar aspect—navigational maps of polar regions.
Equatorial aspect—navigational maps of Africa and the tropical region of South America.