The term chronograph is often confused with the term chronometer. A chronometer is a portable timekeeper that meets certain precision standards. In all later films, Brosnan wore an Omega Seamaster Professional Diver 300M Chronometer (model 2531.80.00). In all later films, Brosnan wore an Omega Seamaster Professional Chronometer (model 2531.80.00). Deblois made his way to the cabin, where he seized a sextant, chronometer and chart. The invention of an accurate marine chronometer revolutionized marine navigation. Testing criteria are based on ISO 3159 which defines a wrist chronometer with spring-balance oscillator. This eliminates chronometer error and watch error corrections. The rate of a mechanical marine chronometer is sensitive to its orientation. In 1761, marine chronometer was invented. The marine chronometer was invented by John Harrison in 1730. John Harrison created the first highly accurate marine chronometer in the mid-18th century. He designed a marine chronometer for Charles II. In fact, the Cal. 727 was certified as a chronometer in some cases. Two other methods of reducing sights are the longitude by chronometer and the ex-meridian method.