We often wonder what speed the Sport Kites are flying.  In the daytime we could fly the kites by two sticks 
and time them with a video camera.  The problem is the sticks are near the ground and kites are flying slower 
by the ground.

But now with the LEDs on the wing tips and a digital camera we can calculate the speed at night in the turns, 
in a climb or in a dive.  The flashing LEDs provide the time and the distance in the pictures.

Speed = Distance/Time

First we will calculate the feet in a second and then change that to Miles per Hour.

To change feet a second to Mph we multiply by 60 for minutes then by 60 for hours.  Then divide by 5280 for miles.

We took some pictures with a digital camera on a tripod and posted them on the ps1kites.com web site.  Most of 
the pictures we took on September 14, 2007 were 10 seconds and you can tell that by the number before the S in 
the name of the picture.  We may take some pictures at 3.2 seconds so the last number is the tenth of a second.

6541r08F100S The first number is the picture number 6541 and the small r is our way of saying we resized the 
picture to fit on the web.  The kite is 08 foot(F) and we sometimes use 10 and 15 foot kites as well.  Last is the 
exposure time which in this case was 10.0 seconds(S).

The kite used in picture 6541r08F100S has lights on the wing tips and the lights are about 8 foot apart.  The LED lights 
flash back and forth at the same rate and the rate can be adjusted with a small pot.  We set the flash rate and are not 
sure of the rate till we count the flashes in the picture.  We counted 69 flashes in ten seconds.  That makes the flash rate 
6.9 flashes in one second.

Now let us look at the picture and note that the kite speed changes, but the space between the lights is the same or 
near the same.  The distance between the lights is 8 feet. We can measure distance in pixels. The picture is just one 
big graph paper when we look at the pixels and all the numbers they have like 283, 341.  The first number is the left to 
right and the second number is the up to down number.  With trigonometry we can use distance formulas on the pixels.
Remember side A squared plus side B squared equals side C squared in right triangles.  In the 3, 4, 5 triangle we have 
3*3=9, 4*4=16, 9+16= 25 and the square root 25 is 5.

We picked some points on picture 6542r08F100S and they are 324, 399 and 351, 399.  The points are on each wing tip 
and 8 foot across.  We picked the points because we will not need trig to see how many points to 8 foot.  We just subtract 
351- 324 = 27 points to 8 foot.  So 27/8 = 3.375 points to a foot.
   
Now let's try to get the speed of the kite as it dove down, we pick the point 329, 364 and 324, 399.  Remember we counted 
69 flashes to 10 seconds and that worked out to 6.9 flashes a second.  We picked the points were the light just turned on one 
of the wing tips. Now what is the speed?  Well how much did it move in one flash 329 - 324 = 5 and 399 - 364 = 35.  It moved 
5 points left and 35 points down. Now we use the trig 5 * 5 = 25 and 35 * 35 = 1225 and add the sides 25 + 1225 = 1250 take
the square root 35.35 points.  We know the 3.375 points to one foot, so we divide 35.35 / 3.375 = 10.48 feet in one flash. So we 
take 10.48 feet times 6.9 flashed for one second and we get 10.48 *  6.9 = 72 feet in a second.  Now to calculate Mph, 
72 * 60 = 4320 feet a minute and 4320 * 60 = 259,200 feet in one hour and 259,200 /  5280 = 49 Mph.