How do I get the speed I’m traveling from 2 sets of GPS coordinates?
bggraves4000 asked:
I’m developing a GPS Windows Mobile application (personal for now, but I might make it public) and I wanted to find out (theory wise) how to get the speed I’m traveling when given 2 sets of coordinates. I would go out and capture 2 coordinates driving at a constant speed, but I was hoping there was a magic formula.
I’m developing a GPS Windows Mobile application (personal for now, but I might make it public) and I wanted to find out (theory wise) how to get the speed I’m traveling when given 2 sets of coordinates. I would go out and capture 2 coordinates driving at a constant speed, but I was hoping there was a magic formula.
There’s no magic formula, except the formula for velocity.
V=D/T where:
V=velocity
D=distance
T=time
Your program needs to read two points, calculate the distance between the points, and then divide it by the time between the readings. You can’t just plug in two coordinates independent from a time reading, which is what it sounds like you want to do.
You probably need some BASIC trigonometric …..
(I can’t believe you know how to write computer program but not knowing this…..)
anyways….first, you need 2 points…assuming you measure those 2 points exactely 1 second apart.
assuming
Point one:
47.64753 degree North
122.38547 degree West
Point two:
47.64822 degree North
122.38585 degree West
you subtract each coord. point 1 and point 2 and you get
0.00069 degree
0.00038 degree
(make sure use absolute value!)
convert your degree to radian first and times the R then you will have distance.
0.00069 degree *3.141592654 / 180 = 1.20428E-05 radian
0.00038 degree *3.141592654 / 180 = 6.63225E-06 radian
Now….Times Radius of the earth of (6,371,000) meters on average
76.72449939 in the J direction (north and south)
42.25407213 in the I direction (east and west)
Now, you find the 3rd side of a right triangle
which is sequare root of 2 other side’s square
so square root of ( 76.72449939 ^2 + 42.25407213 ^2 )
=87.590 meters
so the car traveled 87.590 meters in 1 second
times that 3600 seconds = 315324.97 meters
or approx 315,325 km/hour
it shouldn’t be too hard to convert it to miles
(divide that number by 1.609344 )
you will get 195.93 miles per hour
now, 1 problem is that earth is actually a 3D surface.
so if your GPS get a 3D coordinate (even better) you may want to utilize that……
(You will calculate it base on X,Y, Z instead of just X and Y axis)
the only difference is the last part.
distance is square root of (side 1 ^2 + side 2 ^2 + side 3 ^2 )
Interesting question!