ekg Posted July 17, 2015 Posted July 17, 2015 I know that Russian planes use kilometers and that American planes use nautical miles. Is one any better than the other? I'm curious as to what the advantages / disadvantages are of the different scales.
Eddie Posted July 17, 2015 Posted July 17, 2015 Feet/nautical miles/knots are the international standard units for aviation. The Russians are very much out of the ordinary for using metric units in aviation. Nautical miles/knots just comes for the Maritime world, and have been used since the earliest days of aviation. The only real advantage is that to some areas of the world (US & UK especially), imperial units just make sense, whereas metric units don't in the context of aviation.
ekg Posted July 17, 2015 Author Posted July 17, 2015 Can you explain how imperial makes more sense for navigation? In general I find metric to be OK (it's base 10 etc.). I know that imperial has an advantage of having more divisors between the units etc. Is that ever used in navigation? Or do imperial units somehow correspond to the longitude latitude coordinates?
towsim Posted July 17, 2015 Posted July 17, 2015 One degree along a meridian or great circle corresponds to 60 NM. Means, one minute is a NM. A difference in longitude decreases towards the poles. The rough calculation would be Distance NM = Difference degrees in longitude * cos(latitude) * 60. The circumference of the earth globe would be 360 * 60 = 21600 NM. This distance varies because the globe is not a perfect sphere. [sIGPIC][/sIGPIC]
RoflSeal Posted July 17, 2015 Posted July 17, 2015 (edited) Nautical mile is a unit that is tied to a property of the earth (i.e. it is 1 arcminute on any meridian). Whilst meter is defined by a property of light (how much it travels in a certain time) Edited July 17, 2015 by RoflSeal
ФрогФут Posted July 17, 2015 Posted July 17, 2015 One degree along a meridian or great circle corresponds to 60 NM. Means, one minute is a NM. A difference in longitude decreases towards the poles. The rough calculation would be Distance NM = Difference degrees in longitude * cos(latitude) * 60. The circumference of the earth globe would be 360 * 60 = 21600 NM. This distance varies because the globe is not a perfect sphere. And when would it be needed in flight? It is more of what you are used to. For me it is convenient, that all readings are in the same units in metric, while feet have nothing to do with nautical miles. "Я ошеломлён, но думаю об этом другими словами", - некий гражданин Ноет котик, ноет кротик, Ноет в небе самолетик, Ноют клумбы и кусты - Ноют все. Поной и ты.
X-man Posted July 17, 2015 Posted July 17, 2015 Sweden has historically used Metric units in the air force (m for alt, km for dist). Not sure what we use nowadays since we've been kreeping closer and closer to NATO. 64th Aggressor Squadron Discord: 64th Aggressor Squadron TS: 135.181.115.54
159th_Falcon Posted July 17, 2015 Posted July 17, 2015 Feet/nautical miles/knots are the international standard units for aviation. The Russians are very much out of the ordinary for using metric units in aviation. Nautical miles/knots just comes for the Maritime world, and have been used since the earliest days of aviation. The only real advantage is that to some areas of the world (US & UK especially), imperial units just make sense, whereas metric units don't in the context of aviation. Not really, Eurocopter uses metric units and plenty of planes can be configured on the fly to use metric units. That Imperial units are used is just something that was decided by whoever. And even in aviation, metric units are becoming more and more common because there easier to use. (this is mainly on the technical side of things at the moment though) [sIGPIC][/sIGPIC] The keeper of all mathematical knowledge and the oracle of flight modeling.:)
Yurgon Posted July 18, 2015 Posted July 18, 2015 I know that Russian planes use kilometers and that American planes use nautical miles. Is one any better than the other? I'm curious as to what the advantages / disadvantages are of the different scales. Need... to fight... the incredibly intense desire to... post pictures making fun of... imperial units... Ah, screw it. ;) http://imgur.com/gallery/rFC9s How to teach the metric system to Americans I guess the best argument anyone could possibly make in favor of the imperial system is "that's what I learned, and I intend to stick with it". Either way, as long as some countries keep the imperial system as their primary system of measurement, someone will always be forced to learn another system. OTOH, it's not that difficult. 3 feet are roughly equal to one meter, and with a bit of training and getting used to it, feet and nautical miles become as natural to me as I'm sure meters and kilometers would become to Americans (many virtual Kamov, Sukhoi and MiG-pilots from the US will probably attest to that). :smartass:
AlphaOneSix Posted July 18, 2015 Posted July 18, 2015 I used to be really pro-metric system, and I still am, but not as much. The turning point came when I realized that converting units is generally not that important for many benign, say-to-day applications. For example, if you're driving to the store, and it's a 3 mile trip, why would you need to convert that unit of distance to another number? Who cares how many feet it is? Same with metric...okay it's 5km to the store. Yay, I can instantly convert that to 5,000 meters, but that number is completely irrelevant, nobody is going to say, "Oh, thank goodness I was able to convert that 5km to 5,000m. Imagine if we were using the imperial system!" I will readily admit that there are also lots of situations where it clearly makes things easier to use metric system, and I think in those cases, we should probably completely switch, but I don't think it's quite as big of a deal as many people try to make it.
sobek Posted July 18, 2015 Posted July 18, 2015 (edited) http://imgur.com/gallery/rFC9s Need to suppress urge to make fun of people who think that °C is the SI unit for temperature... :P:D I suppose i failed. :) Edited July 18, 2015 by sobek Good, fast, cheap. Choose any two. Come let's eat grandpa! Use punctuation, save lives!
towsim Posted July 18, 2015 Posted July 18, 2015 (edited) In my last post I tried to answer only the question about Lat/Long and a possible link to nautical miles. Nevertheless, it makes no sense to have different types for units. A common standard is the best argument. I remember the time when I was on a navigation course. We were tortured with navigation problems consisting of countless different measurement units as input arguments. During the last decades there were several attempts to change over to the metric system. The result is was a mix of units but no consequent migration. We have hecto Pascal instead of inches and for visibility we use kilometers instead of nautical miles. For me, it was a settling down to use imperial units. But after a while, it became hard to think in other units. Especially when estimating distances to objects. Finally it is more or less tradition, no technical reason, to stay with imperial units. It is even a question of money to change all the instruments in an aircraft. From my point of view the metric system would make more sense because the entire technical world uses the metric standard (if you are not in a business with the US or England). After the second world war, when the aviation was rebuild in Germany, the entire education was up to the US and partly to England. So it is no magic, that Germany uses the same standards as used in the US. During a stay in US, I had the chance to work together with US military tower controllers and had a visit at their ATC academy. It was interesting to observe, that the procedures and the phraseology I have learned, matches still one to one to the todays US procedures. I am afraid, that the big change comes not before England changes over to drive on the right side. Edited July 18, 2015 by towsim 1 [sIGPIC][/sIGPIC]
fixen Posted July 18, 2015 Posted July 18, 2015 Need to suppress urge to make fun of people who think that °C is the SI unit for temperature... :P:D I suppose i failed. :) But nobody uses kelvin, while it is actually really easy. I guess the numbers would get to big for normal use :huh:
NeilWillis Posted July 18, 2015 Posted July 18, 2015 Nautical mile is a unit that is tied to a property of the earth (i.e. it is 1 arcminute on any meridian). Whilst meter is defined by a property of light (how much it travels in a certain time) How did Napoleon know the speed of light? It was actually based on the circumference of The Earth. Check your history books. As for whether there is an advantage of one form of measurement over another. How could there be? All units of measurement are random human rationalisations, and to suggest one is better than another is a little pointless. Imperial measurements are based on things like the length of your thumb, the length of your foot, the span of an arm. Metric systems are scientific, and are the basis of SI units for that reason. A plane flies just as fast in NM as it does in Kilometres per hour. It just might use more of one than another. The only reason imperial measurements have persisted long past their sell by date is that one nation dominated nautical domains for hundreds of years, and could impose it's methods, and language on the world. We all use imperial measurements, time conventions and English for navigation purely for that reason, and not because it has any advantages.
sobek Posted July 18, 2015 Posted July 18, 2015 How did Napoleon know the speed of light? It was actually based on the circumference of The Earth. Check your history books. That's a thing of the past, it's definition has evolved with our understanding of nature, the most current definition stemming from 1983. It is now defined as the ~2.9e8th fraction of the distance that light travels in vacuum during one second. All units of measurement are random human rationalisations, and to suggest one is better than another is a little pointless. I disagree. Imperial units are more prone to induce error when humans make calculations with them. I'm not going to claim that the SI is perfect, but it damn sure is superior to the Imperial System. Good, fast, cheap. Choose any two. Come let's eat grandpa! Use punctuation, save lives!
fixen Posted July 18, 2015 Posted July 18, 2015 http://imgur.com/ua9xmtI Except NASA went metric :music_whistling: 1
NeilWillis Posted July 18, 2015 Posted July 18, 2015 I disagree. Imperial units are more prone to induce error when humans make calculations with them. I'm not going to claim that the SI is perfect, but it damn sure is superior to the Imperial System. I can't argue that the imperial system is a lot more difficult to work with. The metric system is far more practical because it is all in base 10. It was created after the age of enlightenment, whilst the imperial system stems from far back in history. Both systems are just rationalisation and quantification of the physical world however, and therefore do precisely the same things.
Home Fries Posted July 18, 2015 Posted July 18, 2015 (edited) And when would it be needed in flight? It is more of what you are used to. For me it is convenient, that all readings are in the same units in metric, while feet have nothing to do with nautical miles. I used nautical miles all of the time in flight. As was posted, one minute of latitude is one nautical mile, so you have a scale built into your chart*. You can very easily determine range to a feature on a chart by using your pinkie and index fingers as an improvised divider, then mark 1 degree of latitude on your chart and "walk" the distance from your DR position to the object. If you're not concerned with FOD and you have a real set of dividers, it's even more convenient. Using nm, you can cut or fold your chart any which way (i.e. make a strip chart that follows your route) and still use it as a navigation tool because wherever you look you can find your distance scale. While feet may be less intuitive than meters for altitude, feet (and yards) can also easily be derived from the nautical mile. One nautical mile is 6000 feet or 2000 yards (as opposed to the 5280 ft in a statute mile, which gets into the realm of the confusing). Aviators don't use yards that much, but the ship/sub drivers do when talking about distances within 5 nm, so it helped (in my case) to be proficient in both. EDIT: One last thing about feet: When talking about a cannon pipper, US fighters often have a ring around the pipper that is solid outside of 2nm, then "counts down" in feet by starting from the 12 o'clock position and reducing counterclockwise. This way, you can see where the ring ends, match it to a clock face (e.g. 9 o'clock), and that clock face is your distance to the target in thousands of feet. Since there are 6000 ft in 1 nm (and 12000 ft in 2 nm) this makes perfect sense. *Assuming you're using a Lambert Conformal chart and not a Mercator projection. Edited July 18, 2015 by Home Fries One last thing about feet... 1 -Home Fries My DCS Files and Skins My DCS TARGET Profile for Cougar or Warthog and MFDs F-14B LANTIRN Guide
NeilWillis Posted July 18, 2015 Posted July 18, 2015 Except NASA went metric :music_whistling: Well to be strictly accurate, some of NASA did, and the rest didn't, which cost the space program dearly.
Exorcet Posted July 18, 2015 Posted July 18, 2015 In my last post I tried to answer only the question about Lat/Long and a possible link to nautical miles. Nevertheless, it makes no sense to have different types for units. Not really. Intuitiveness can be more important than convertibility. Even in science, you have "strange" units like angstroms, solar mass, mols, speed of sound, etc for various reasons. Sometimes it's just easy to think in those units, like saying something is 4 solar masses instead of number^some_two_digits kilograms (or even some arbitrary amount of yottagrams). Also, changing units based on what is being measured can help reduce ambiguity I suppose. If range is in miles and altitude is in feet, you shouldn't really get measurements for one mixed up with the other. Awaiting: DCS F-15C Win 10 i5-9600KF 4.6 GHz 64 GB RAM RTX2080Ti 11GB -- Win 7 64 i5-6600K 3.6 GHz 32 GB RAM GTX970 4GB -- A-10C, F-5E, Su-27, F-15C, F-14B, F-16C missions in User Files
Yurgon Posted July 18, 2015 Posted July 18, 2015 http://imgur.com/ua9xmtI Haha, point taken. :D I actually have a claim against the metric system as well, but will suggest an upgrade right away. One thousand watts are called a kilowatt. One thousand kilowatts are called a megawatt. One thousand meters are called a kilometer. One thousand kilometers are called one thousand kilometers. One thousand grams are called a kilogram. One thousand kilograms are called a ton. Since, obviously, this doesn't make a whole lot of sense, why don't we just stick to the prefixes we already have and thus call... - one thousand kilowatts a megawatt. - one thousand kilometers a megameter. - one thousand kilograms a megagram. It may sound weird at first, but it's actually inherently correct.
Davee Posted July 18, 2015 Posted July 18, 2015 Can you explain how imperial makes more sense for navigation? In general I find metric to be OK (it's base 10 etc.). I know that imperial has an advantage of having more divisors between the units etc. Is that ever used in navigation? Or do imperial units somehow correspond to the longitude latitude coordinates? My understanding is that base 12 is better for navigation. Curvatures, 360 degree circles, tangents etc. They don't divide well by base 10.
Davee Posted July 18, 2015 Posted July 18, 2015 But nobody uses kelvin, while it is actually really easy. I guess the numbers would get to big for normal use :huh: Nobody is very generic. Astronomers and physicists do all the time considering what they deal with.
pepin1234 Posted July 19, 2015 Posted July 19, 2015 I my god. How good I feel with the metrics units. The use of the imperial units in aviation is more than a dictatorial idea. There is any reason to decide the imperial units over the metrics units. I feel much better using the metrics units, doing everything. in Aviation, driving a car, measuring a door, everything... [sIGPIC][/sIGPIC]
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