Changes

The nautical mile is used mainly for maritime and aviation purposes because of its relation to the degrees of latitude.  A '''knot''' is used to describe speed in nautical miles per hour. The term knot is sometimes erroneously used instead of nautical mile (knot being thought a diminutive of nautical).  However, the name derives from the ancient practice of throwing a log overboard with a knotted rope attached.  The knots were made at fixed intervals and as the rope was paid out the number of knots that passed through a sailor's hands in a fixed time were counted to give a measure of the speed. <ref>http://www.onlineconversion.com/faq_07.htm</ref>   

The nautical mile is used mainly for maritime and aviation purposes because of its relation to the degrees of latitude.  A '''knot''' is used to describe speed in nautical miles per hour. The term knot is sometimes erroneously used instead of nautical mile (knot being thought a diminutive of nautical).  However, the name derives from the ancient practice of throwing a log overboard with a knotted rope attached.  The knots were made at fixed intervals and as the rope was paid out the number of knots that passed through a sailor's hands in a fixed time were counted to give a measure of the speed. <ref>http://www.onlineconversion.com/faq_07.htm</ref>   

As ships and aircraft travel through a fluid medium their speed is relative to the speed of the water or air and may be referred to as "boatspeed" or "airspeed".  Consequently there are several additional definitions of speed which are given in knots: '''speed of a vessel over the ground''' (SOG)<ref>http://www.lowrance.com/Support/Glossary/glossary.asp#Speed-Over-Ground</ref> describes the speed with reference to geographical location and '''velocity made good''' (VMG) describes its rate of progress toward a distant point<ref>http://www.lowrance.com/Support/Glossary/glossary.asp#Velocity-Made-Good</ref>.

As ships and aircraft travel through a fluid medium their speed is relative to the speed of the water or air and may be referred to as "boatspeed" or "airspeed".  Consequently there are several additional definitions of speed which are given in knots: '''speed of a vessel over the ground''' (SOG)<ref>http://www.lowrance.com/Support/Glossary/glossary.asp#Speed-Over-Ground</ref> describes the speed with reference to geographical location and '''velocity made good''' (VMG) describes its rate of progress toward a distant point<ref>http://www.lowrance.com/Support/Glossary/glossary.asp#Velocity Made Good</ref>.

==Metric Mile==

==Metric Mile==