How accurate is the Great Circle Mapper?

[leny]

Is the Great Circle Mapper website accurate to the single mile? What system do airlines use to determine the number of miles they will credit for flights?

 

[og]

GCM is close but it never seems to exactly match the miles paid by airlines. Murphy Law states that when you are right on the QF SC level, GCM will show its over the line but QF will come in under the line.

 

[bambbbam2]

I did a flight recently and gcm said 604 miles so I was concerned but qf agreed.. Still I don't think it's guaranteed 100%..

 

[oz_mark]

GCM is close but it never seems to exactly match the miles paid by airlines. Murphy Law states that when you are right on the QF SC level, GCM will show its over the line but QF will come in under the line.

Of course, if your are trying a redemption it will work the opposite way

 

[simongr]

I think the question is not so much whether GCM is accurate - more whether the airlines use the GCM calcs - which often they do not.

 

[og]

And where on the airport do you take the point used for mileage? If two airports have 4 km runways, simplisticly, there is potentially 8km variation in this alone.

 

[Keith009]

There's a mileage calculator on Sabre and it usually differs from the GCM by 4-8 miles per sector.

 

[straitman]

And where on the airport do you take the point used for mileage? If two airports have 4 km runways, simplisticly, there is potentially 8km variation in this alone.

Maybe from the airfield datum point would be logical :!: