Robinson projection
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The Robinson projection is a map projection used for geographic maps.
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[edit] Overview
Presented by Dr. Arthur H. Robinson in 1963, it is classified as a pseudo-cylindrical projection by reason of its straight parallels, along each of which the meridians are spaced evenly. The central meridian is also a straight line; other meridians are curved. Robinson specified the projection to be constructed by referring to a table of cartesian coordinate values at specific intersections of latitude and longitude. Intermediate locations are to be found by interpolation; see below for details. This method reflects the way he developed the projection as a series of trials, iterating until he settled on the meridian shapes and parallel spacing most pleasing to him. To contrast, most other projections are formulated as mathematical equations. Several formulaic representations of Robinson's projection have appeared in the literature as alternatives to the look-up tables.
[edit] History
Robinson was a professor in the Geography Department at the University of Wisconsin in Madison from 1945 until he retired in 1980. He developed the projection under commission from Rand McNally because they were not satisfied with the ability of existing projections to create intuitive depictions of the entire world. Rand McNally thenceforth made extensive use of it in many atlases and books. It was the first major map projection to be commissioned by a large private corporation.[1] The projection was initially named by Robinson as "orthophanic" (meaning correct-looking) but the name never caught on, and it quickly became known as the Robinson projection. It has also been referred to as The Pseudocylindrical Projection with Pole Line, because the North and South poles are represented as a line as opposed to points as they are on other projections. National Geographic Society adopted it for their world maps in 1988 but abandoned it ten years later for the Winkel Tripel. Many educational institutes and textbooks followed National Geographic's example in adopting the projection, and most of those still use it.
[edit] Strengths and weaknesses
Like many projections, the Robinson has advantages, and like all projections, it also has disadvantages. The projection is neither equal-area nor conformal, abandoning both for a compromise the creator felt produces a better overall view than could be achieved by adhering to either. The meridians curve gently, avoiding extremes, but thereby stretch the poles into long lines instead of leaving them as points. Hence distortion close to the poles is severe but quickly declines to moderate levels moving away from them. The straight parallels imply severe angular disortion at the high latitudes toward the outer edges of the map, a fault inherent in any pseudocylindrical projection. However, at the time it was developed, the projection effectively met Rand McNally's goal to produce appealing depictions of the entire world. Today the Winkel Tripel Projection is more popular.
[edit] See also
- Cartography
- Gall-Peters projection
- Nautical chart
- Mercator projection
- Transverse Mercator projection
- Winkel Tripel projection
- Map projection
[edit] Specification
The projection is defined by the table:
| Latitude | PLEN | PDFE |
|---|---|---|
| 00 | 1.0000 | 0.0000 |
| 05 | 0.9986 | 0.0620 |
| 10 | 0.9954 | 0.1240 |
| 15 | 0.9900 | 0.1860 |
| 20 | 0.9822 | 0.2480 |
| 25 | 0.9730 | 0.3100 |
| 30 | 0.9600 | 0.3720 |
| 35 | 0.9427 | 0.4340 |
| 40 | 0.9216 | 0.4958 |
| 45 | 0.8962 | 0.5571 |
| 50 | 0.8679 | 0.6176 |
| 55 | 0.8350 | 0.6769 |
| 60 | 0.7986 | 0.7346 |
| 65 | 0.7597 | 0.7903 |
| 70 | 0.7186 | 0.8435 |
| 75 | 0.6732 | 0.8936 |
| 80 | 0.6213 | 0.9394 |
| 85 | 0.5722 | 0.9761 |
| 90 | 0.5322 | 1.0000 |
The table is indexed by latitude, using interpolation. The PLEN column is the length of the parallel of latitude, and the PDFE column is multiplied by 0.5072 to obtain the distance of that parallel from the equator. Meridians of longitude are equally spaced on each parallel of latitude.
[edit] References
- Robinson, A. A New Map Projection: Its Development and Characteristics, International Yearbook of Cartography 14, 1974, pp. 145-155.
- John B. Garver Jr., "New Perspective on the World", National Geographic, December 1988, pp. 911-913.
- John P. Snyder, Flattening The Earth - 2000 Years of Map Projections, The University of Chicago Press, 1993, pp. 214-216.
[edit] External links
- Table of examples and properties of all common projections, from radicalcartography.net
