Comments on: How do I get the speed I’m traveling from 2 sets of GPS coordinates? http://www.foxfire1.com/speed-gps/how-do-i-get-the-speed-im-traveling-from-2-sets-of-gps-coordinates No more tickets Sun, 01 Aug 2010 03:12:59 -0500 http://wordpress.org/?v=2.8.4 hourly 1 By: TJ C http://www.foxfire1.com/speed-gps/how-do-i-get-the-speed-im-traveling-from-2-sets-of-gps-coordinates/comment-page-1#comment-680 TJ C Tue, 09 Feb 2010 02:07:59 +0000 http://www.foxfire1.com/speed-gps/how-do-i-get-the-speed-im-traveling-from-2-sets-of-gps-coordinates#comment-680 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!<br><b>References : </b><br>I'm an engineer. I don't do math. I set it up and send it to the mathematicians. ;) 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!
References :
I’m an engineer. I don’t do math. I set it up and send it to the mathematicians. ;)

]]> By: justsomeguy http://www.foxfire1.com/speed-gps/how-do-i-get-the-speed-im-traveling-from-2-sets-of-gps-coordinates/comment-page-1#comment-679 justsomeguy Tue, 09 Feb 2010 02:00:59 +0000 http://www.foxfire1.com/speed-gps/how-do-i-get-the-speed-im-traveling-from-2-sets-of-gps-coordinates#comment-679 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.<br><b>References : </b><br> 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.
References :

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