Throughout the centuries, curiosity about the earth has led explorers to embark on journeys around the world. Adventures that were undertaken by celebrated global circlers like Ferdinand Magellan and Sir Francis Drake are well known. More recently, global and space flights such as the Voyager airplane and the first artificial satellite, Sputnik I, also roused much public interest.
In this chapter we portray the routes of three of the above circumnavigations. It is a challenge to show routes on a small-scale world map. We begin by asking the following questions:
What areas on the earth does the route predominantly transverse (e.g., equatorial, northern or southern hemisphere)? The distance between and shapes of areas along the route should be well preserved on the map.
What information should be included on the map so that the route can be interpreted correctly?
What projection(s) should be selected and specially designed to help the map reader visualize the spherical character of the global circler's journey? Because the route is continuous and global, it imposes limitations on projection design. For example, the trip should be shown on a world map without interruption; also, the entire route is important and no one segment can be slighted.
Magellan's Expedition -- The First Circumnavigation
Ferdinand Magellan sailed with five ships and some 250 men in September 1519 from the port of Seville, Spain. He continued to the Cape Verde Islands, crossed the Atlantic Ocean, discovered the turbulent strait that now bears his name in October 1520, entered the calm ocean that he named Pacific in November 1520, passed Guam to reach the Philippines in the spring of 1521, and was killed in a local conflict shortly afterward. Elcano led the only surviving ship and 17 men returning to Seville in September 1522 via the Indian Ocean and around the Cape of Good Hope. This was the first circumnavigation.
Magellan's trip began in the northern hemisphere. While the crew sailed primarily along middle and lower latitudes, they also reached the southern extremities of Africa and South America. A projection that emphasizes the spherical nature of the trip in these regions is desirable.
The Raisz Armadillo projection has been chosen to depict the Magellan-Elcano route because it looks three-dimensional. It compresses areas at the periphery of the map and hides some areas altogether (Figure 8-1). Raisz tilted the equator down (see Figure 3-1) to emphasize land, but the tilting can be upward, as is done here.
In some cases, it is important to show the entire sphere; one of Canter's projections can be used to reduce shape distortion of continents. Figure 8-2 shows his 1989 projection termed the "minimum-error polyconic projection with equally spaced parallels and pole line." Like the Raisz projection, it gives the impression of a sphere spread out onto a flat surface.
The Flight of Voyager
In December 1986, public interest was captivated by the flight of Voyager, a non-stop airplane flight that originated and ended at Edwards Air Force base in California. The journey spanned nine days traveling in an east-to-west direction on a path that ranged between the equator and 35° N.
For the book "Voyager" by Yeager and Rutan the flight was displayed on a strip Mercator projection. Two other possibilities are to utilize the Robinson and the Lambert Azimuthal Equal-Area projections. The Robinson and the Lambert Azimuthal Equal-Area projections are chosen to portray this global flight. The Robinson projection shows the entire earth and preserves the shapes of areas well (Figure 8-3). The Voyager's near-equatorial path is shown with relatively little distortion.
If we choose to emphasize the circular nature of the flight of the Voyager, a good choice is a Lambert Azimuthal Equal-Area map centered on a point near the pole to depict the uninterrupted flight path realistically (Figure 8-4). This design shows the entire earth and also gives an impression of three dimensions.
Sputnik I - The First Artificial Satellite
While east-west circumnavigation captured the human imagination in the past, north-south circling is of great commercial and strategic importance in modern times.
The launching of the Soviet Sputnik I in October 1957 began a new era of high technology. Sputnik (meaning fellow traveler [of the earth] ) was the first artificial satellite. It traversed a north-south path ranging between parallels 65° N and 65° S; each orbit of the earth lasted approximately 92 minutes (Figure 8-5).
Orbiting satellites travel steadily along what would be great-circle routes except that the earth moves along its orbit and also spins beneath them, so the satellite groundtracks spiral around the earth. Their circumnavigation may journey from almost pole to pole, incline relative to the equator, or align with the equator.
Generally, cylindrical or rectangular projections are not ideal choices for showing the entire earth because they present significant distortion in the polar areas. However, they can show effectively the north-south traversals of satellites, which follow consistent cyclical patterns. The projected Sputnik path on the map should emphasize this regularity visually.
The Miller Cylindrical projection shows the entire earth in a rectangle (Figure 8-5). The successive orbits of Sputnik I are identical and repeating sinuous curves. The path of one orbit is highlighted. On this map, the highlighted orbit begins at the equator near Borneo, moves toward the north, and then moves southward. When it returns from the south to cross the equator, the satellite is about 24° west of its previous crossing, since the earth has rotated relative to the satellite. The successive northbound paths are omitted to simplify the map.
Lastly, the Snyder Cylindrical Satellite-Tracking projection is a good choice to depict the satellite path as a set of straight lines (Figure 8-6). Areas beyond the northern-and southernmost points of the satellite track cannot be shown by this projection. The diagonal lines depict the paths of Sputnik as it moves from north to south. The same orbit highlighted in Figure 8-5 is emphasized. As in Figure 8-5 the northbound paths are omitted.
Mapping the routes of global circlers is an interesting but by no means easy task. The selection of an appropriate projection is greatly facilitated, however, with the use of modern computer programs.
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