Agile Estimating and Planning

Chapter 19. Monitoring the Release Plan

“The stars might lie, but the numbers never do.”

—Mary Chapin Carpenter, “I Feel Lucky”

Ancient sailors had two problems. First, they had to know their latitude—that is, their north-south position on a map. Second, they had to know their longitude, or east-west position. Determining latitude by observing the North Star was relatively easy and had been done as early as 300 BC. Longitude presented a more difficult problem because it relied on the use of a relatively accurate clock, or chronometer. Unfortunately, there were no sufficiently accurate chronometers (especially that would fit and work aboard a ship) until the early eighteenth century.

Before the invention of the chronometer, a sailor could only ...