Articles | Index

Different Miles and How They Came to Be 2010-03-18
Under the Roman Empire, Rome became the center of the western world. All roads led to Rome and all distances were measured from Rome. The distances were based upon one thousand Roman paces of the Roman soldier. A Roman pace is equal to two of our steps and very near 64 inches. The Latin for a thousand paces is 'mille passus' from which we derived the word mile. Many different miles of differing length.have existed from the old London mile of eight furlongs. This was measured by German 'feet' but at the time of Queen Elizabeth a shorter foot was used giving a distance of 5280 feet. which is now the statute mile. The first paths for ships were called Porotan Charts. These were lines drawn across the Mediterranean between the coastal ports. Where many of these lines crossed the mapmakers would draw wind roses. The wind rose initially varied but settled on the eight points. The predecessor to the compass rose and our eight-wind direction terms. Thales of Miletus (640-546BC) made a gnomonic projection (use of shadows) of the region where he lived. Hipparchus in the 2nd century BC had used sterographic (showing heights) and orthographic projections (perspective). Eratosthenes in 3rd century BC calculated the size of the earth circumference to be 24,000 miles. He developed a 16 point wind rose and use of 'degree". He also wrote a description of known world. Ptolemy, a 2nd century Greek, made a world map and made a world size error when he calculated size of world's circumference to be only 18,000 miles. Jean Picard did not correct this until 1669, 200 years after Columbus. Eratosthenes' calculations had been lost to the western world. Ptolemy used the first conic projection plane map with the top as north. This made possible drawing of rhumb (one direction) lines from point to point on the globe. He devised the 60 minute and 60 second divisions of the 360 degrees in a circle. A mile at sea, on this world of Ptolemy, was essentially equal to a mile on the land. The length of a statute mile was 1000 (mille, from the Latin) Roman paces. A Roman pace is two of our steps. Each Roman road had occasional small obelisk statues placed to indicate the distance from Rome much as Mexico today does from Mexico City. Hence, statute miles. A 1466 Chart of Nicolaus Germanus divided the degree into 60 equal spaces called miles. This was based upon an earth of 18,000 mile circumference and gave us a nautical mile the same length as a Roman statute mile. Other cartographers including Hipparchus and Mercator gave us a world with an overlying grid with numerical markings of longitude and latitude. Gerardus Mercator (Gerhard Kremer), Flemish, in 1569 drew world globe map with 180 degrees E/W longitude 0 to 90 N/S latitude. He made errors which were corrected by Edward Wright who published the computations required as "Meridional Parts" and made this knowledge universal. In combination, we now had a world, which could be mapped in degrees of longitude and latitude. Each degree of longitude had divisions of 60 miles equal to a statute mile and each mile was again divided into 60 units called minutes and each minute was again divided into 60 units called seconds. This was the kind of map and scale used by Columbus. The navigators of his time had not the timing device to make possible the exact determination of longitude. The best 15th Century data available to Columbus came from Ptolemy. The error by Ptolemy directly resulted in Columbus' declaring that he had reached and was exploring India. Columbus thought he had sailed through enough degrees of longitude to reach India. He may well have, had the world been 18,000 statute miles in circumference. When the world was computed to be 24,000 statute miles in circumference all the degrees and their divisions were longer and did not conform. More accurate computation of the world's circumference kept changing and finally came to 24,902 statute miles. The circumference of the earth has always been measured as 21,600 nautical miles (360 degrees X 60 nautical miles per degree). However, the individual nautical mile has ballooned by nearly a third through this recalculation of the earth's size. The Nautical or Sea Mile is the length of a minute of latitude. The U.S. Nautical Mile at one time was 6,080.27 feet. This figure was revised to 6,076.i feet/ This came to be know as the International Nautical Mile. The British use the Admiralty Mile of 6,080 feet. Some countries still use the 1929 International Hydrographic Bureau mile of 6,076.097 feet. The Geographical Mile uses the Equator as a great circle and a minute mile is 6,087.1 feet long. For many of the same reasons the U. S. has failed to convert to metric, later cartographers decided to use statute miles for land and the expanded nautical mile at sea. Now we can see the background for the difference between nautical and statute miles and Columbus' reasoning. We have Columbus sailing around an earth at least 1/3 larger than he was led to believe. Based on available knowledge Columbus was quite justified to assume that he had actually reached and explored India. For the navigator, it is very important that distance only be measured along the lines of longitude, which has evenly spaced tick marks throughout. The elongated orange peel appearance of the region between lines of longitude means that various latitude lines will have tick marks at differing intervals although always 60 ticks per degree. Only at the Equator do the tick marks correspond to the size of those along the lines of longitude. Johann Henrich Lambert from Alsace devised the Lambert conformal conic projection in which the line you draw is the way you go. This is the charting used on aircraft. As with any flat map of a round surface it has areas of inaccuracy. Sectionals are most inaccurate (stretched) in the six inches at the top and bottom. The center ten inches of the sectional for 5 inches up to five inches down from center is somewhat contracted in size. Comment		External Links  Recent articles Power-on Stalls No lower that 1500 #39; BR Takeoff configuration BR Induce stall with heading maintained U U 10 degrees when inducing stall with... Where's The Problem? When an instructor becomes upset over a student #39;s performance the student could well consider that the problem lies with the instructor An... VFR Midairs 82 occur by one aircraft being overtaken from the rear BR 35 occur with convergence less than 10 degrees BR ... Pilotage and Dead Reckoning Course within 3 nautical miles BR Altitude U U 200í BR Arrival within 5 minutes BR Heading within 15 degrees... 1998 Statistics li B Over 20 of all G A fatal accidents had weather as contributing factor BR ... Emergency Trim Use If the elevator is locked as with a control lock the use of trim will be backwards Any use of the trim will be as an... Unusual Attitudes P During the proficiency phase of hood work #39;unusual attitudes #39; should be practiced This means that you will put on the hood close his... Performance Sheet ASEL Weight and balance BR CG at gross takeoff______CG at gross landing____ BR Shift weight from______ to _____ BR New CG ______ B BR ... Turns About a Point P Some students do better if the point is selected at the intersection of to right angle roads This instead of a lone tree helps maintain ... Spin Awareness (Discussion) Flight situations where spins may occur BR Recognize a spin and apply recovery technique BR Techniques specific to aircraft BR power off and flaps up... Calming Flying Anxiety P Anxiety is generalized fear Your body prepares you to run fight or act to protect yourself Your heart and blood pressure rise blood... Statistics on General Aviation Accidents ol li 51 of pilots were between 40 49 BR li 71 were private pilots BR ... Minimum Equipment List P I Reference FAR Part 91 I P P P Knowledge of required instruments and equipment for day night VFR... The Competence of Incompetence With the advent of a new study as to what constitutes competence there is a new fear by the self assured that they may be among ... Mad As Hell And Taking It P In flying we react in an emergency as we first learned to react When we show anger we react as we first learned to react Just... Illusions - Natural Illusions P B Rain B BR Rain gives the illusion of being higher than you actually are Combined with haze you will fly... WD-40 and Cleaning P The use of WD 40 is not recommended on aircraft It is not recommended because only a light lubricant is left after the solvents evaporate ... Practice Illusions P B Autokinesis B BR On a dark night fly toward a single light Student is to stare only at the light... Illusions - IFR for VFR pilots P The purpose of IFR training is to be able to read interpret the instruments and fly accordingly The introduction of the VFR student to the... Advice From Over 30 Years Ago B The performance of any complex activity such as flying an airplane requires the learning of highly conditioned responses ... Trim Use P Correct use of the trim requires that control pressures be applied to hold the desired flight attitude Then the trim is adjusted to relieve present control... Teaching The FAA Way I have never seen the 60 14 textbook I assume it is the revised Flight Instructor Handbook I once made a complete summary of ... Coffee P Half of the American population is addicted to coffee 25 drink ten or more cups a day Quitting coffee is both difficult and painful... Its About Time... The next major step in aviation measurement came from the Greeks about 2500 years ago The Greeks sought rules for the way number ideas seemed to work ... Inspections P FAR 43 11 a b Type description date total time signature certificate type and number; approval or disapproval for return ... Where To Go; What To Do P You can find whom to interview by talking to people around the airport Pretty soon certain names will keep coming up Those are the people... Carbon Monoxide P Is poisoning due to the exhaust fumes resulting from carbon burning with insufficient oxygen to produce complete oxidation The resulting gas has one atom of carbon... Steep Turns Va or POH entry speed into 360 turn with bank of 10 5 degrees of 45 U U 100 feet ... Why Ground Reference? P One of the weakest parts of flight instruction is the failure of the instructor to let the student know the #39;why #39; of some of the... The PTS Everything about the Practical Test is a given If you have studied the PTS you know what is going to happen You may not know when or just how... Trim Tab Inventor Also known at the servo trim was invented by Anton Flettner a German aeronautical engineer He worked for the Zeppelin Company in Germany... Unusual Attitude Recoveries Nose up Recover with pitch down add power level wings BR Nose down Recover with reduced power level wings pitch to level ... 1999 Nall Report li B Landings are the source of most accidents but few injuries BR li For every mile traveled airplanes... Run-up Control check BR Engine check BR Instrument settings BR Uses checklist BR Airspeed distances review BR Emergency and departure review... Parking P The number one region of aircraft accidents is getting into a parking space Some pilots seem to think it necessary to make a little jog toward... Introduction to Ground Reference P During the time that I am practicing flap descents and go arounds I try to make at least one descent over a gently curved channel or road... Pre-takeoff Considerations P B 1 Gross Weight and Center of Gravity B BR Gross weight is the empty weight plus useful load You must check... Self-Doubt is Normal B Every so often the instructor finds a student who is going through a phase of flying that is very disturbing to the student... Hypoxia P An adult will breath in 3 000 gallons by volume of air per day This includes 600 20 of total gallons of... Minimum Controllable No maneuvers below 1500í BR Stall horn whimpering at all times BR Power added as required to hold altitude in 10 degree maximum banks BR ... Growing Up As A Pilot It takes more than time to grow and mature as a pilot Judgment cannot be measured just by time but by the number of successful ... Dealing with Delays One of the advantages of learning to fly in the fall is the greater probability of weather delays A pilot learns to live with and accept delays of any kind... Why Accidents Happen ul li 75 of accidents involve poor pilot judgment with reference to his ability knowledge or capability BR... Good Instruction Communication BR Knowledge and ability to explain BR Ability to demonstrate BR Patience BR Motivation... VFR to IFR Options P What to do If you #39;re on top do the four C #39;s Climb communicate confess comply If fuel and weather... 1999 Was A Very Good Year 1908 general aviation accidents BR 342 were fatal accidents BR 7 05 accidents per 100 000 hours of flying BR ... Not Making Progress? P I doubt that there is a pilot flying who has not at one time or another felt the twinge of doubt that his learning curve is not... Aviator's Lies ul li The weather will be all right BR li We will be on time maybe even early BR ... Medicine P Any over the counter medication whose name ends in quot;ine quot; should be checked in a flight medical examiner for use before flying Beware of... Night Flight (Discussion) Use of checklist BR Preflight BR Chart reading BR Hazards and precautions BR Lighting systems of plane and airport BR...  Related Links
©2010 4VFR.COM, All Rights Reserved	Powered by 4vfr.com