What standard for calculation of miles/distance?
Jun 9th, 2006, 07:07 AM
#1
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What standard for calculation of miles/distance?
Does anyone know of an independent website (or other source)that will give the airport-to-airport mileage? I suspect some under-estimation in a couple of recent flights, but a website like MapQuest, of course, will only give you highway-bound land measurements.
Jun 9th, 2006, 07:11 AM
#2
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IMHO, this is the best there is:
http://gc.kls2.com/
You need to know the three letter codes for the airports and in case you don't there is a search capability.
http://gc.kls2.com/
You need to know the three letter codes for the airports and in case you don't there is a search capability.
Jun 9th, 2006, 12:11 PM
#4
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There may be a little bit of discrepancy between airline miles and the more accurate Great Circle Mapper. But usually just a few miles, and you may come ahead. For example, on the popular (for my family) route of IAH-EWR-HKG, CO gives us 1,415 + 8,060 miles; while GC Mapper says 1,400 + 8,065.
The easiest way for airline to cheat you is on the so-called "direct" flights, when there's nothing direct about them except they're of the same flight number. For example, if I fly CO89 IAH-EWR-PEK, I will only get about 7,200 miles for IAH-PEK; but I would have flown for over 8,200. I can give more examples on CO alone.
There are ways to get around it, but you need to be aware of this first.
The easiest way for airline to cheat you is on the so-called "direct" flights, when there's nothing direct about them except they're of the same flight number. For example, if I fly CO89 IAH-EWR-PEK, I will only get about 7,200 miles for IAH-PEK; but I would have flown for over 8,200. I can give more examples on CO alone.
There are ways to get around it, but you need to be aware of this first.
Jun 9th, 2006, 03:58 PM
#5
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Easiest one I've found is http://www.webflyer.com/travel/milemarker/
And yes, I have my suspicions about how some airlines calculate.
And yes, I have my suspicions about how some airlines calculate.
Jun 9th, 2006, 07:15 PM
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For United, Northwest or American Airlines, here is a tool:
http://www.faremetrics.com/distcalc.html
http://www.faremetrics.com/distcalc.html
Jun 9th, 2006, 10:12 PM
#7
I use webflyer for estimating mileage. To get the actual mileage for United, I use the Multi-City option at united.com. The search results give the mileage for each segment.
webflyer told me that LAX-IAD-LAX-LHR is exactly 10,000 miles. If that is high by 1 mile that would be bad. united.com gave me the good news, it is actually 10041 (enough to earn two CR1 upgrades).
webflyer told me that LAX-IAD-LAX-LHR is exactly 10,000 miles. If that is high by 1 mile that would be bad. united.com gave me the good news, it is actually 10041 (enough to earn two CR1 upgrades).
Jun 10th, 2006, 01:14 AM
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First - under estimation? what's that? the airline(s) decides what the actual mileage is, not you, not some mileage calculator site. The airline's web site usually lists the mileage for each segment, so that's the time to make a mental note of what you will be getting.
As <b>rkkwan</b> explained, if miles are important, you have to be very careful about "direct" flights. "Direct" flights are not the same as "non-stop". What happens is that on some routes the airline(s) like to promote a "direct" flight, i.e. AA has a SFO-LHR flight, to compete with UA's non-stop, but the flight is actually SFO-ORD-LHR under the same flight number, but instead of getting mileage for SFO-ORD-LHR(5799), the pax will only get mileage for SFO-LHR(5367) because both segments are under the same flight number. In this case the difference is not too bad, but there are other instances where it could be significant, so you have to be careful with that.
Other than that, the Great Circle Mapper link I provided will work for most mileage estimates within a mile or 2 and in most cases it's identical to the airline's number. In fact I have only found couple of segments (out of hundreds and hundreds) that the GCM and AA were off by a mile or two. That is very acceptable to me when I'm trying to figure out a OneWorld award which is based on distances, not regions/countries.
Last year I found a routing that satisfied my needs and it came in at under 20K miles, so the cost was 180K miles. If it was over 20K miles than the award would have been 230K miles. Big difference. With the help of GCM I knew that the routing was something like 19,987 miles and guess what? after calling AA and getting the same routing with them, the total came in at 19,987 miles. The agent was amazed as to how I came in that close......
So, for your basic mileage information needs (with ANY) airline one can't beat GCM. On occasion it may be off by a mile or 2, but that is very acceptable. Airlines themselves don't agree on the number of miles on some routes so there is no such thing as a "standard, uniform" mileage. Airline A may list a route as 1000 miles and airline B may list it as 1005 miles. That's just the reality.
Don't sweat the little differences. As long as it's within couple of miles, you have to accept it.
As <b>rkkwan</b> explained, if miles are important, you have to be very careful about "direct" flights. "Direct" flights are not the same as "non-stop". What happens is that on some routes the airline(s) like to promote a "direct" flight, i.e. AA has a SFO-LHR flight, to compete with UA's non-stop, but the flight is actually SFO-ORD-LHR under the same flight number, but instead of getting mileage for SFO-ORD-LHR(5799), the pax will only get mileage for SFO-LHR(5367) because both segments are under the same flight number. In this case the difference is not too bad, but there are other instances where it could be significant, so you have to be careful with that.
Other than that, the Great Circle Mapper link I provided will work for most mileage estimates within a mile or 2 and in most cases it's identical to the airline's number. In fact I have only found couple of segments (out of hundreds and hundreds) that the GCM and AA were off by a mile or two. That is very acceptable to me when I'm trying to figure out a OneWorld award which is based on distances, not regions/countries.
Last year I found a routing that satisfied my needs and it came in at under 20K miles, so the cost was 180K miles. If it was over 20K miles than the award would have been 230K miles. Big difference. With the help of GCM I knew that the routing was something like 19,987 miles and guess what? after calling AA and getting the same routing with them, the total came in at 19,987 miles. The agent was amazed as to how I came in that close......
So, for your basic mileage information needs (with ANY) airline one can't beat GCM. On occasion it may be off by a mile or 2, but that is very acceptable. Airlines themselves don't agree on the number of miles on some routes so there is no such thing as a "standard, uniform" mileage. Airline A may list a route as 1000 miles and airline B may list it as 1005 miles. That's just the reality.
Don't sweat the little differences. As long as it's within couple of miles, you have to accept it.
Jun 10th, 2006, 04:22 AM
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Besides the IAH-EWR-PEK I mentioned above, two other CO "direct" flights can cheat with you a lot of miles
CO7 is SAT-IAH-NRT-GUM, even though it's three different planes. They'll give you <b>7,293</b> instead of 500 (actual miles 191) + 6,643 + 1,558 = <b>8,701</b>.
But worse is CO51 FRA-EWR-IAH-EZE on 2 different planes. They'll give you <b>7,134</b> instead of 3,869 + 1,415 + 5,062 = <b>10,346</b> for a deficit of almost 3,000 miles each way.
CO7 is SAT-IAH-NRT-GUM, even though it's three different planes. They'll give you <b>7,293</b> instead of 500 (actual miles 191) + 6,643 + 1,558 = <b>8,701</b>.
But worse is CO51 FRA-EWR-IAH-EZE on 2 different planes. They'll give you <b>7,134</b> instead of 3,869 + 1,415 + 5,062 = <b>10,346</b> for a deficit of almost 3,000 miles each way.
Jun 10th, 2006, 05:53 AM
#11
If estimation is involved then underestimation is a possibility. I might start using the GCM site because it gave the same distances as united.com. The sites may be computing the great circle arc with the same reference ellipsoid.
I like the GCM site because it sums the flight segments (and doesn't transpose the last two digits of LAX-LHR like I did when I added it up).
I use united.com because I am interested in United Mileage Plus miles and I do not recommend using it for any other purpose.
I actually found an error on webflyer once. The value shown for NRT-NGO was fare too big, a few times larger than the shinkansen distance. I got e-mail reply saying they would look into it. Within just a couple of hourse they corrected it.
I like the GCM site because it sums the flight segments (and doesn't transpose the last two digits of LAX-LHR like I did when I added it up).
I use united.com because I am interested in United Mileage Plus miles and I do not recommend using it for any other purpose.
I actually found an error on webflyer once. The value shown for NRT-NGO was fare too big, a few times larger than the shinkansen distance. I got e-mail reply saying they would look into it. Within just a couple of hourse they corrected it.
Jun 10th, 2006, 06:05 AM
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I saw codeshared flights operated by 1 airline yet sold by 1 or 2 other airlines as their own, list different number of miles. The difference is never big, maybe 5 or 10 miles total, but that just affirms my point in my earlier post. Same flight, operated by airline A, codeshared by airlines B and C, and depending on which airline you buy the ticket from, you may get few less or few more miles.
Jun 10th, 2006, 06:33 PM
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AAFF, I never understand your 'tood when you leap to slap down a question/questioner ("the airline, not you, decides the mileage"
. Duh! I'm not an idiot who expected to tell the airline how many miles I should be credited -- it was purely a matter of curiosity. Wondered, too, if all airlines flying the same routes come up with the same mileage.
And of course, what I was looking for was an independent calculator -- NOT provided by the airlines -- against which I could test my hypothesis of underestimation. Or heck, why not: overestimation (like that'll happen).
So, in any case and otherwise, thank you all for the useful links -- webflyer was a winner!
. Duh! I'm not an idiot who expected to tell the airline how many miles I should be credited -- it was purely a matter of curiosity. Wondered, too, if all airlines flying the same routes come up with the same mileage.And of course, what I was looking for was an independent calculator -- NOT provided by the airlines -- against which I could test my hypothesis of underestimation. Or heck, why not: overestimation (like that'll happen).
So, in any case and otherwise, thank you all for the useful links -- webflyer was a winner!
Jun 10th, 2006, 10:06 PM
#14
AAFF answered your question in the first reply to your post.
There are multiple ways to compute the flight distance between two points. There are multiple answers but they won't vary by much, and they will all be correct approximations. The mathematics of the computation are pretty standard, but the model used for the Earth could differ (for instance should we compute the distance on a sphere? what diameter? ...). The accuracy of the values used for the two locations could differ. And shoudld we use mean sea level elevation, ground level, or some height above ground?
If the mileage that your airline credited to your account is different by more than 20 miles from what AAFF's site gives or what webflyer gives then you could check your FF statement to make sure that they didn't make a mistake and used the wrong airports (e.g. using ATL instead of ATH). That could be a source of big discrepancies. I doubt very much that this happened.
Reread the explanations above about direct flights and how they are handled by FF programs. It is very likely the reason for a big discripancy in the mileage you expected.
Am not sure if anybody mentioned this earlier, but another reason for big differences would be the amount of miles credited for a partner's flight.
I got AAFF's last point that ANA and United might have different mileage computations for LAX-NRT. If I book a flight on united.com I will get united's value credited to my United account. If I book on fly-ana.com I might get ANA's value credited to my United account. The values may differ, but they won't differ by much. (I actually believe I will get the United mileage in either case, assuming the fare earns full credit).
What could make a big difference with partner airline credits is a rule that limits the mileage credit depending on the fare code. For example, I might get 50% credit on my United account for the mileage flown on a super promotional ANA fare. Another rule might give only actual mileage for a 200 mile flight and not the usual minimum 500 miles.
The best source for the mileage you should earn, the one that beats all others, is the airline that credits the miles. It doesn't hurt to check other sources, though, just to make sure there was no mistake. You should expect differences.
There are multiple ways to compute the flight distance between two points. There are multiple answers but they won't vary by much, and they will all be correct approximations. The mathematics of the computation are pretty standard, but the model used for the Earth could differ (for instance should we compute the distance on a sphere? what diameter? ...). The accuracy of the values used for the two locations could differ. And shoudld we use mean sea level elevation, ground level, or some height above ground?
If the mileage that your airline credited to your account is different by more than 20 miles from what AAFF's site gives or what webflyer gives then you could check your FF statement to make sure that they didn't make a mistake and used the wrong airports (e.g. using ATL instead of ATH). That could be a source of big discrepancies. I doubt very much that this happened.
Reread the explanations above about direct flights and how they are handled by FF programs. It is very likely the reason for a big discripancy in the mileage you expected.
Am not sure if anybody mentioned this earlier, but another reason for big differences would be the amount of miles credited for a partner's flight.
I got AAFF's last point that ANA and United might have different mileage computations for LAX-NRT. If I book a flight on united.com I will get united's value credited to my United account. If I book on fly-ana.com I might get ANA's value credited to my United account. The values may differ, but they won't differ by much. (I actually believe I will get the United mileage in either case, assuming the fare earns full credit).
What could make a big difference with partner airline credits is a rule that limits the mileage credit depending on the fare code. For example, I might get 50% credit on my United account for the mileage flown on a super promotional ANA fare. Another rule might give only actual mileage for a 200 mile flight and not the usual minimum 500 miles.
The best source for the mileage you should earn, the one that beats all others, is the airline that credits the miles. It doesn't hurt to check other sources, though, just to make sure there was no mistake. You should expect differences.
Jun 10th, 2006, 10:25 PM
#15
I launched into all of that last post after rading "like that'll happen". I might have just said: "it is likely that it will happen" that the airline's value is higher than webflyer's or some other source.
Jun 10th, 2006, 10:33 PM
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Whatever works for you.....
AA - TPA-ORD = 1012 miles
Great Circle Mapper - TPA-ORD = 1012 miles
Webflyer - TPA=ORD = 1010 miles
AA - TPA-DFW = 929 miles
GCM - TPA-DFW = 929 miles
Webflyer - TPA-DFW = 927 miles
AA - MIA-LAX = 2342 miles
GCM - MIA-LAX = 2342 miles
Webflyer - MIA-LAX - 2340 miles
but, as I said whatever works for you. Accuracy is not the strong point of webflyer, ease of use is, so it all depends what you're looking for.
AA - TPA-ORD = 1012 miles
Great Circle Mapper - TPA-ORD = 1012 miles
Webflyer - TPA=ORD = 1010 miles
AA - TPA-DFW = 929 miles
GCM - TPA-DFW = 929 miles
Webflyer - TPA-DFW = 927 miles
AA - MIA-LAX = 2342 miles
GCM - MIA-LAX = 2342 miles
Webflyer - MIA-LAX - 2340 miles
but, as I said whatever works for you. Accuracy is not the strong point of webflyer, ease of use is, so it all depends what you're looking for.
Jun 10th, 2006, 10:35 PM
#17
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I've already given an exmaple of an airline giving more. CO credits 1,415 between their two hubs of IAH-EWR, while all the independent sites mentioned on this thread gives 1,400 or 1,398.
This is not insigificant. That's a very busy route for CO with lots of elites flying it. So, not only are they crediting a lot more miles, but also the bonus miles and EQMs.
This is not insigificant. That's a very busy route for CO with lots of elites flying it. So, not only are they crediting a lot more miles, but also the bonus miles and EQMs.
Jun 11th, 2006, 08:48 AM
#18
The significance of the difference is relative to what you are using the numbers for. For the OP's purposes any of the sites mentioned above will give an answer that is good enough.
If CO credits 1415 and a different website says the distance is 1398, and another says 1425, then you should conclude that the value credited by CO is reasonable. Those differences are not large enough to be significant.
But the value given by CO is the EXACT value because CO is the authority in this case and the others sites are not, so they should be treated as being inexact, i.e. approximations.
Since the CO value of 1415 is within the range of plus/minus 20 miles of the other computations then it doesn't look like CO made an error.
If CO credits 1415 and a different website says the distance is 1398, and another says 1425, then you should conclude that the value credited by CO is reasonable. Those differences are not large enough to be significant.
But the value given by CO is the EXACT value because CO is the authority in this case and the others sites are not, so they should be treated as being inexact, i.e. approximations.
Since the CO value of 1415 is within the range of plus/minus 20 miles of the other computations then it doesn't look like CO made an error.
Jun 11th, 2006, 11:27 AM
#19
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I really hesitate to keep this going, since my original post was just a matter of curiosity. (Never really wanted an in-depth probe of specific airlines or routes, or a reminder that whatever the airline says, goes.)
HOWEVER -- since there are some discrepancies, one might speculate (not assert, mind you) that one possible reason for variation could be something as simple as customary approach and traffic-management programs. For example, if CO is "giving away" an extra 15 miles, perhaps it's including a margin for approach and departure patterns in addition to the point-to-point mileage. Perhaps other airlines calculate from furthest airport-property boundary to nearest airport-property boundary. Who knows?
Heck, a difference of just a couple of miles with DFW could be accounted for simply by looking at different runways!
HOWEVER -- since there are some discrepancies, one might speculate (not assert, mind you) that one possible reason for variation could be something as simple as customary approach and traffic-management programs. For example, if CO is "giving away" an extra 15 miles, perhaps it's including a margin for approach and departure patterns in addition to the point-to-point mileage. Perhaps other airlines calculate from furthest airport-property boundary to nearest airport-property boundary. Who knows?
Heck, a difference of just a couple of miles with DFW could be accounted for simply by looking at different runways!
Jun 11th, 2006, 04:42 PM
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<b>soccr</b>,
your theory about circling the airport or different runways does make sense, except, regardless of how many times the plane circles the airport or which runway(s) it uses for take-off and landings, the particular airline you are flying will still only give you the same number of miles. I have been on flights were we cicrled ORD for about 1/2 an hour because of ATC hold and AA still only gave me 1012 miles when flying from TPA or whatever the stated miles are when flying from London or Tokyo.
The miles are always the same, regardless which way the the particular flight routes on any given day. Flying from TPA in summer/fall is always adventurous because of tropical storms/hurricanes in the gulf. I'm scheduled to fly early Tuesday with a connection in MIA and DFW to Osaka, so once again it could be fun with the tropical storm scheduled to make landfall early Tuesday morning just north of Tampa. Sometimes we fly in straight line, sometimes the captain is forced to go around (especially on TPA-DFW routes), but at the end I still only get 929 miles.
your theory about circling the airport or different runways does make sense, except, regardless of how many times the plane circles the airport or which runway(s) it uses for take-off and landings, the particular airline you are flying will still only give you the same number of miles. I have been on flights were we cicrled ORD for about 1/2 an hour because of ATC hold and AA still only gave me 1012 miles when flying from TPA or whatever the stated miles are when flying from London or Tokyo.
The miles are always the same, regardless which way the the particular flight routes on any given day. Flying from TPA in summer/fall is always adventurous because of tropical storms/hurricanes in the gulf. I'm scheduled to fly early Tuesday with a connection in MIA and DFW to Osaka, so once again it could be fun with the tropical storm scheduled to make landfall early Tuesday morning just north of Tampa. Sometimes we fly in straight line, sometimes the captain is forced to go around (especially on TPA-DFW routes), but at the end I still only get 929 miles.
