BOOKEND / By JOHN NOBLE WILFORD
Fold -- No, Click -- Here
fter the publication of one of my books, ''The Mapmakers,'' a friend enthused, ''You have told me everything I ever wanted to know about maps, except how to refold them.'' Nothing this side of a long run on the best-seller list, I suppose, pleases an author of a new book more than witty flattery. One clings to it as a consolation for not having scored big in sales. But time eventually has rewarded me with a sense of satisfaction that is deeper than consolation: the satisfaction of being the author of a book with a long life.
I like to think that ''The Mapmakers'' has aged well. Enjoying the general approval of critics and readers, it settled down to fairly steady sales for the better part of two decades, in both hardcover and paperback. Some geography professors put it on their course reading lists. After a while, the modest royalty checks that kept coming were like found money; selective memory had largely blanked out the years of reporting, research and writing that went into producing the book. If writers were good at cost accounting, they would probably never start a book.
Now ''The Mapmakers'' is being given a new life. A revised edition, expanded to include new scholarship in the history of cartography and especially the latest technological developments in the making and use of maps, was published in September.
My editor at Alfred A. Knopf, Ashbel Green, tells me that revised editions of general nonfiction books are rare in publishing. Knopf puts out an average of only one a year, and these are usually dictionaries, travel guides, cookbooks and other self-help works. Textbooks are another matter -- many are revised every three years.
In my case, the idea of a new edition emerged from a continuing interest in the subject, almost despite myself. Many authors seem to feel that when they have finished a book they have exhausted the subject, or have been exhausted by it. I felt the same way at first. But in my day job in journalism, there is a tradition: once you write about a particular subject, you are the expert in the office, the one called on to write similar articles and review other books on the subject. People who make and study maps also would bring their work to my attention. All this kept me involved in cartography, and made me aware that there was more to say.
For one thing, I learned more about the obscure contributions to early mapmaking by the Chinese and Arabs, and, thinking ''I wish that were in my book,'' filed the information away. I was ''saving string,'' another practice of journalists. However, when I reviewed in these pages the first volume of ''The History of Cartography,'' a monumental series still in the works by the University of Chicago Press, I was left with mixed feelings. It would have saved me so much time researching mapping's early history. But its detail and authority are awesome and might have dissuaded me from presuming to attempt a popular treatment of the subject.
Even unrelated reading sometimes swung me back to maps. In Beryl Markham's evocative ''West With the Night,'' I came across the aviator's paean to maps. The map may be only paper and ink, she wrote, ''but if you think a little, if you pause a moment, you will see that these two things have seldom joined to make a document so modest and yet so full with histories of hope or sagas of conquest.''
In all honesty, though, today's mapmakers themselves are responsible for my book's revival in a revised edition. They and the new technologies at their command created the need. And when the editors of National Geographic magazine asked me to write an article on the ''revolutions in mapping,'' I seized the opportunity, realizing it would force me to gather and evaluate material for a possible book revision. As Dr. Johnson might have said, nothing concentrates a journalist's mind so much as an assignment with a deadline.
While I was on a visit to the Library of Congress, it struck me that the history of the art and science of cartography was an open-ended story that must be updated from time to time, and especially now. The old maps on the shelves of the library's geography and map division pulled me again into cartography's rich past. The reading room snapped me back into the present, and the future. A couple of young men were hunched before computer screens, scrutinizing a map their fingers at the keyboard had just created.
Their map could show the trail to a trout stream, the streets of their neighborhood or the incidence of cancer by county in any particular state. The map could be ephemeral, vanishing at the next click on the keyboard. It could be altered on the screen -- details added or highlighted, scale and perspective changed and then printed out. Someone sitting at the computer screen could generate a custom-made map in the time it must have taken early chartmakers to draw a single rhumb line as a bearing for mariners navigating a wide sea.
Ralph E. Ehrenberg, who was then chief of the map division, said that he had seen many radical changes in cartography since he was a young man converting aerial photographs into maps, the cutting-edge technology in the middle of the 20th century. Speaking in soft librarian tones, he mused: ''Today, you can put in one of our floppy disks and, with each image that comes on the screen, you are creating a new map. To me that's revolutionary.''
When my book was first published in 1981, I anticipated some of the new uses of computers and space-age remote sensing in expanding what could be mapped and expediting the making of maps. But, like people in the field, I never imagined the pace and magnitude of change that is now occurring.
Electronic technology is changing everything about maps today. So much of the mapping data is no longer collected by foot-slogging surveyors but by satellites. They take detailed pictures and detect variations in the land with sensors that see beyond the range of human vision. They bounce radar signals to measure the contours of cloud-covered or forested terrain and to penetrate the soil to archaeological remains hidden beneath. Other sensors plumb ocean depths and detect the reflected-light signatures of vegetation, snow cover and soil moisture. All this information is transmitted in electronic bytes, which computers then process into maps.
Navigation satellites give cartographers the longitude, latitude and elevation of just about any place on earth. Portable global positioning devices, drawing on the satellite signals, have been called the most important development in the history of surveying. In little more than an instant, surveyors can use the instruments to fix a position with pinpoint precision, something that not long ago would have taken hours or days of celestial sightings and ground measurements.
Data for the content of maps and information about where exactly it belongs come together in computer-stored archives. Every shoreline and boundary, every highway and street, everything from the ocean floor to the top of Mount Everest, has been recorded as so many electronic bytes. Software known as a Geographic Information System is the mastermind of this new cybercartography. It converts existing paper maps into digital form, adds updated information from new surveys, selects and analyzes data required for a map and then displays it all in graphic form at the proper geographic locations.
Mapmakers and geographers have weighed the implications of cybercartography with a mixture of excitement and anxiety. The printed map itself is no longer the principal repository of geographic information; that function has passed to computer databases. The computer-literate can call up a growing volume of geographic data and, choosing a certain theme and scale, create their own maps. Digital cartography has empowered every person to be his or her own mapmaker, with direct access to various map databases. These user-cartographers are expected to grow in number, and to stretch the scope and influence of maps.
A few of the claims for the new technologies of cybercartography may prove to be extravagant. But which ones? That may sort itself out in time for another revision, and an even longer life, for ''The Mapmakers.''