Proofing with Maps

August 8, 2015

While proofing for Distributed Proofreaders, I often find myself opening up a mapping application to locate rivers, towns, buildings, forts, streets, etc. that are mentioned, described, or central to a project.  Sometimes it’s to figure out where they are. Sometimes it’s to try and see what’s being described.


For example, Early Western Travels, 1748-1846, Volume XXIII, describes some rock formations that the footnote identified as being in Dawson and Valley Counties, Montana. Using that information, I was able to view a photo of the rock formations. I’ve also found remote tiny towns that still exist in the American West — one even had a preserved historical district.

Florizel’s Folly (in progress at DP) led me to Brighton, EnglandYellowstone’s Living Geology: Earthquakes and Mountains (also in progress) to Old Faithful.

I posted in the DP forums about this and found another proofreader who was using mapping software to locate parks that were mentioned in old bird books as locations of certain birds. This person was interested in whether the parks have the same birds.

Of course, I look at maps because I love maps. So starting with a specific reference point from a book, I can get lost for half an hour or more exploring, envisioning, and virtually visiting. Anywhere. And how exciting when I get a chance to visit in person a site I’ve visited before via mapping software; for example, the Pony Express Statue in Sacramento Old Town.

If you haven’t tried this before, do! You may find yourself addicted.

This post was contributed by WebRover, a DP volunteer.

Mathematical Geography by Willis Ernest Johnson

November 27, 2010

Before the advent of coordinated universal time and internationally-recognized time zone boundaries, practical, day-to-day considerations of time measurement quickly became entangled in geographical, political, historical, and legal problems of surprising recalcitrance.

If you live in the northern hemisphere, does the sun pass due south of you every 24 hours? Perhaps surprisingly, no! An hour is 1/24 of a sidereal day, the time required for the earth to rotate once with respect to the stars. Because the earth orbits the sun, the sun’s position on the celestial sphere traverses a circle once per year. Consequently, the mean solar day is shorter than the sidereal day by a factor of roughly 1/365.25: The sun therefore passes due south on average every 23 hours, 56 minutes, 4 seconds. The actual length of the solar day varies seasonally because the earth’s orbit is not circular and the dates of perihelion and aphelion (when the earth is closest or furthest from the sun) do not coincide with the solstices (when the north pole is tipped most nearly toward or away from the sun).

A related phenomenon is said to have confounded Ferdinand Magellan’s crew briefly upon return to Spain after circumnavigating the globe. Their careful reckoning gave the date of September 6, 1522, but the Spaniards assured them the date was the 7th. Eventually the crew realized they had lost a day over their long voyage by traveling west, with the sun. Today we would say Magellan lost a day crossing the date line.

Civilizations successfully used local (solar) time for millennia. Only when consistent time measurements were required over extended longitudes did standard time become important. Of course, time standards were not immediately or universally adopted. Consequences ranged from minor confusion for travellers to legal cases with substantial financial stakes.

During the late Nineteenth Century in the United States, railroads and cities used their own time conventions for many years. When Mathematical Geography was written, the vicinity of El Paso Texas used four systems of time, due to the confluence of three U.S. time zones and an entirely separate Mexican standard time used in Juarez, across the Rio Grande.

In 1902, thirteen lawsuits were brought in the courts of Kentucky over the wording of fire insurance policies. In one case, the policy expired at noon on April 1, 1902, but left unspecified whether solar or standard time was to be reckoned. On the date in question, a warehouse fire began at 11:45 A.M. standard time, namely at 12:02:30 P.M. local time. Nearly $20,000 of insurance money hung in the balance of the court’s decision. Such improbable occurrences were not as rare as one might expect. Willis’s book does not divulge the outcome of these cases, but does highlight the need for pedantic attention to issues we might all regard as too obvious to warrant detailed consideration.

In the modern world of the global positioning system, universal time, and largely undisputed geopolitical boundaries, we easily forget that divisions of time and space are nothing more than social agreements. The earth has no intrinsic clocks convenient for international travel and commerce, nor many geographical features that unambiguously separate neighboring states, provinces, territories, or countries.

Mathematical Geography is not a mere catalogue of amusing events and curious factoids, but a clear, engaging, and systematic exposition of the shape and movement of the earth as an astronomical body, and the consequences for time-keeping, map making, and geodesy. Written in 1907 for use in American secondary schools and for teacher preparation, the book intertwines purely scientific issues of astronomy and geography with the historical growth of the United States in the 1800s as the political entity expanded across the North American continent, and with then-current legal and practical issues related to time and place. Much of the factual content is up-to-date, and even the remainder should be of historical interest.

Despite the book’s imposing title, the mathematical content is light, entailing only trigonometry, plane geometry, and basic algebra. Mathematical Geography is easily accessible to a modern reader with a good high school education. A curious and intelligent younger reader can also learn much, skipping brief mathematical derivations as needed or even learning useful mathematics in a realistic context.

This enjoyable book deserves, and earns, the attention of anyone who wants to understand more about the planet we inhabit and how the earth’s shape and motion affect our daily lives.

This review was contributed by DP-volunteer adhere.

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