Gps Question

[Over-Talk]

Nice variety of answers......but completely useless.

 

Please re-read his question......he is not asking about great circles or rhumb lines.

 

Think of the question this way....to go the shortest distance, direct from Toronto to Bangkok, you would need to pass through the center of the planet Earth.

Is this the distance that the satellites calculate ??

 

My answer is NO......you won't need a very large drill rig to get to Bangkok if you use a GPS!!

 

I suspect the satellites are programmed to think of the Earth as a large flat surface, not a round object.

 

Now that we have that sorted, you guys can go back to discussing Great Circles over a flat surface, transverse mercators etc etc.

 

Remember that 212 Wrench is a teacher by trade, and is often more interested in how you answer the question, rather than what you answer.

How did I do Wrench?

Did I earn a University Degree, so that I can learn to fly a 407 around Niagara Falls?

[CJM91]

Nice variety of answers......but completely useless.

...

I suspect the satellites are programmed to think of the Earth as a large flat surface, not a round object.

 

Not to put too fine a point on this old thread but you just added to the list, perhaps tongue in cheek.

 

GPS satellites are not programmed to think of the earth at all but just send out coded signals so that the receiver can calculate a position from 3 , or preferably 4+, satellites. It is the receiver's navigational software only that figures out where you are and where you're going. Being truly global, it is all about spherical trigonometry, not flat surfaces. The earlier comments about GCR are correct.

 

GPS altitude is calculated either as above a smooth mathematical surface called the ellipsoid or above a convoluted mathematical model of the earth's surface at your location which is itself derived from the ellipsoidal height. Since neither of these are highly accurate in a local sense (but very good overall), a GCR could be out slightly but for our purposes not noticeable.

 

Cheers . . . .

 

 

[RonnyRotor]

Not to put too fine a point on this old thread but you just added to the list, perhaps tongue in cheek.

 

GPS satellites are not programmed to think of the earth at all but just send out coded signals so that the receiver can calculate a position from 3 , or preferably 4+, satellites. It is the receiver's navigational software only that figures out where you are and where you're going. Being truly global, it is all about spherical trigonometry, not flat surfaces. The earlier comments about GCR are correct.

 

GPS altitude is calculated either as above a smooth mathematical surface called the ellipsoid or above a convoluted mathematical model of the earth's surface at your location which is itself derived from the ellipsoidal height. Since neither of these are highly accurate in a local sense (but very good overall), a GCR could be out slightly but for our purposes not noticeable.

 

Cheers . . . .

Ya Thats exactly what I was going to say !!