# A Little Logic/Math Puzzle for Those who are Bored

##### Diabloii.Net Member
A Little Logic/Math Puzzle for Those who are Bored

Here's a math problem for somebody to figure out...

The airline I work at has outfitted all its aircraft with state-of-the-art GPS equipment. This equipment is capable of telling you how far it is from your present position to a fixed facility on the ground. It can also take your current groundspeed and tell you how long it would take you to fly to this facility. So, for instance, it might say we are 254.4 miles from Anchorage airport, and we would be there in 34 minutes.

Now. Last week, on a flight, I noticed something odd. We had the GPS unit set to measure the distance to an object on the ground BEHIND us. We were moving farther away from the object. The GPS unit confirmed this because the distance between us and the object kept increasing as we moved farther away. However, we noticed that the TIME required to fly to the object was DECREASING. So what situation would be occurring to make this happen? How could we move farther away from something, while at the same time, the time it takes to travel to it decreases? THe object on the ground is stationary. The situation that causes this to happen is very routine and not some wierd, far-fetched explanation, and is also very normal. It is not a problem with the GPS; under this situation this phenomenon is to be expected.

So, what is the situation?

#### Steel_Avatar

##### Diabloii.Net Member
I would assume that the GPS system is calculating the time it would take to get to that reference point, based on your current vector. So since you are travelling away, it calculates the time required as being the 'long way round' the circle, sotospeak. Thus, as you travel away from the reference point, you are reducing the distance to it in the forward direction.

##### Diabloii.Net Member
You're exploiting some of the properties of the earth very close to the North pole I'd guess.

#### Pierrot le Fou

##### Diabloii.Net Member
I believe it'd have to do with the pole as well (assuming north since you're in Alaska) and the curve orf the earth, though I'd have to know more about how GPS works to be sure...

#### asdf

##### Diabloii.Net Member
the gps unit doesn't do negatives? it takes your positive groundspeed and just divides it by the distance to the object
if that was the case, and the plane were accelerating...

#### {KOW}Spazed

##### Banned
Yea I would say that it is saying how long it would it would take to go in a complete circle.

Just curious how does math fit into this?

EDIT: I see the slash in the title now.

#### BSJoker

##### Diabloii.Net Member
well, if the plane is far enough away, combined with the earth rotating on its axis, maybe that way. also have to factor in the eletromagnetic fields from the earth and such things. plus if there was something in the way that could bounce the signals from the plane or bend them like gravity from the earth.......yes gravity can bend things like light or radio waves.

other than that i have no idea

EDIT: wait i swear i just thought of this, what if the plane is moving towards the satalite?