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Ground Speed Algorithm, need help!

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Brantel

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Can one of you math geniuses or people with experience developing ground speed algorithms tell me if it is possible to calculate a ground speed based on the following GPS information being available:

East/west velocity direction
East/west velocity magnitude
North/south velocity direction
North/south velocity magnitude
 
A squared plus B squared equals C squared, remember that from high school?

No, I am old.... :p

I knew the answer was simple and staring me right in the face, I have been sick and up for 3 days with no sleep and can't concentrate. Sucks getting old!

I think I was getting hung up with the fact that both my vectors are GPS variables that are not influenced by the wind. (they are the true vectors out of the box) but now I see that it does not matter the same equations work.

Matt and Greg, now help me with my question about velocity vector. Maybe that one is harder?
 
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No, I am old.... :p

I knew the answer was simple and staring me right in the face, I have been sick and up for 3 days with no sleep and can't concentrate. Sucks getting old!

I think I was getting hung up with the fact that both my vectors are GPS variables that are not influenced by the wind. (they are the true vectors out of the box) but now I see that it does not matter the same equations work.

Matt and Greg, now help me with my question about velocity vector. Maybe that one is harder?

What does the data look like. Is it x degrees at x1 kts and y degrees at y1 kts?

You can break each one down to an orthogonal coordinate system, add the components then it is square root of the sum of the squares for the vector magnitude.
 
What does the data look like. Is it x degrees at x1 kts and y degrees at y1 kts?

You can break each one down to an orthogonal coordinate system, add the components then it is square root of the sum of the squares for the vector magnitude.

It is

E(90°) or W(270°) @ "x" meters/sec
and
N(0°) or S(180°) @ "y" meters/sec
 
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It is

E(90?) or W(270?) @ "x" meters/sec
and
N(0?) or S(180?) @ "y" meters/sec

OK easier, but make the direction in degrees heading for the formula.

This will explain better than I will.

Doing it will be quicker than reading to the bottom. Just have a calculator with sine and cosine functions.
 
I made a spreadsheet to calculate the distance between two lat-long points in the .gpx file for my Garmin Virb Elite and then calculate the speed between them based upon the 1 second sample rate. The distance is:

=ACOS(SIN(C3)*SIN(C4)+COS(C3)*COS(C4)*COS(F3-F4))*180*60/PI()

Where C3 is the first latitude in radians and C4 is the second latitude in radians. F3 and F4 are the longitudes, also in radians.

The speed (in Knots) is the above distance divided by 3600 for a one second interval between lat-lon data.
 
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Once I got my head out of the pseudoephedrine fog, this was incredibly easy.

Thanks guys for the help!

Still working on getting my head around the velocity/flight path vector one.
 
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