The next time that your car does not deliver you to the address that you specified to your global positioning system (GPS), don’t blame TomTom, Garmin, OnStar, Magellan or Rand McNally.
All of these GPS brands are tied to the Global Navigation Satellite System that provides location and time information for any place on earth that has an unobstructed line of sight to at least four of the many designated satellites that encircle the planet. The GNSS “map” is based on a location’s distance from the center of the earth and its relationship to latitude and longitude lines.
When making calculations, the mathematical constant is the point at the center of the earth. That never changes. Imagine a ball within a ball. The inner ball is a perfect circle (really a sphere) and its center is the midpoint of its diameter. The outer ball may not be a perfect sphere, but it is divided into sections by lines running from its north pole to its south pole (longitudinal lines) and running in concentric circles based on its equator, which is the largest circle (latitudinal lines).
The equation for making calculations for various places on the outer ball becomes complicated because, while the orientation point in the inner ball remains constant, the surface of the outer ball may move in irregular patterns.
Location, location, location
The calculations for global positioning systems began during the 1960s. Revisions were made in 1973, and the U.S. Department of Defense used 24 satellites to establish a global system in 1995, called Full Operational Capability. The following year, President Bill Clinton established the Interagency GPS Executive Board to manage the system as a “dual-use” national asset. In essence, this meant that GNSS could be used for civilian as well as military purposes.
Since the late 1990s, all of the systems mentioned at the beginning of this column (TomTom, Garmin, etc.) have utilized GNSS to provide information to their users. Consequently, people who possess any of these devices have been able to get in their cars, give the device the address of a desired location, and then depend on their cars to deliver them to the correct place.
But Australia may be changing all that. Here’s why. The surfaces of our continents are located on the outer ball of our theoretical two-ball system. And, while the satellites operate according to their relationship to the earth’s center (the center of the inner ball) and fixed coordinates (on longitudinal and latitudinal lines) on the outer ball, the shell of the outer ball is constantly changing.
Super-smart mathematicians have been able to take these factors into consideration in designing algorithms that continually relay data to various earth stations. But, the “outer ball” is actually made up of a number of moving sections, called tectonic plates. These plates glide over the mantle, a rocky layer that lies above the core (the “inner ball”). This is the theory of plate tectonics.
A moving target
The theory was first introduced by Alfred Wegener in 1912, but it was not fully developed until the 1970s. Nicholas van der Elst of Columbia University’s Lamont-Doherty Earth Observatory calls plate tectonics the unifying theory of geology. The basic idea is that “all geologic features (are) driven by the relative motion of these tectonic plates,” according to van der Elst.
The plates are in constant movement because hot material near the earth’s core rises, and colder mantle rock sinks. Van der Elst says, “It’s kind of like a pot boiling on a stove.” The convection drives plate tectonics through a combination of pushing and spreading within oceans and pulling and sinking at certain other zones. The “Ring of Fire,” a series of volcanoes that surrounds the Pacific Ocean, is one of these zones. The combination of actions seems to affect Australia more than the other continents.
The Australian plate is the fastest moving of the continental plates on the earth’s surface. Originally, this plate was part of the Asian subcontinent, and it split off about three million years ago. It is still moving. Today it travels northward at nearly three inches a year, dragging the continent closer to the equator and disrupting the GNSS enough to distort the system, which is based on Australia’s position in 1994. Australia is now five feet closer to the rest of the world than it was when global positioning was instituted.
Blame it on Australia
Writing for Business Insider, Simone M. Scully notes, “While five feet doesn’t seem like a whole lot, it is still enough to disrupt global navigation satellite systems … putting the continent out of sync. This affects not only the GPS maps on smartphones, but also delivery drones, farmers, meteorologists, and even automated cars.”
This happens because the maps of many countries are based on global lines of longitude and latitude that are fixed to points on their surfaces, not the mathematical Cartesian coordinates based on the earth‘s center. So, as Scully points out, “as the plates move, this means that over time, local coordinates become out of sync with the global (Cartesian) coordinates.”
Earlier this year, scientists began recalculating all of Australia’s coordinates, and they hope to finish the task by year’s end. Then, in 2020, the “fixed plate system” will be replaced by a flexible system that periodically determines global positions using the Cartesian coordinates. In a BBC interview, Dan Jaksa of Geoscience Australia said, “Once we have a system that can deal with changes over time, then everybody in the world could be on that same system.” Meanwhile, when issues of time and space get fouled up, just blame it on Australia.
After I had gotten too far into writing this column to back out, it occurred to me that I should have paid more attention to my instructors in solid geometry and trigonometry in high school and at least cracked the cover of my geology and astronomy textbooks in college. Corrections, reprimands, and expressions of indignation may be sent to the e-mail address j_glynn at att.net.