I have water velocity data taken in an ENU (East, North, UP) or XYZ coordinate system. The data is contained in 3 columns like this:
E N U
1 3 .1
2 5 .2
2 6 .1
-1 4 .1
-2 4 .1
So the first column represents velocity (in m/s) in the East (or X) direction (negative numbers represent velocity in the West (or -X) direction. The second column indicates velocity in the North (or Y) direction. And the 3rd column represents velocity in the Up (or Z direction).
The data is scalar, but I'm assuming I want to end up with speed and directional data. For ease of understanding, if I were to just consider 2 dimensional data (ignore the Z or up data), is it acceptable to add the E and N data to get useful magnitude and directional data?
For example if in the last row East is -2 and North is 4. So I've got 2 m/s West and 4 m/s North. But does the number 2 (-2 + 4) mean anything?
Or do I need to use $a^2 +b^2= c^2 = 4 +16= 20 \rightarrow \sqrt{20}= 4.47$ But If I were to do this, then I loose the - sign (West direction) information, and it would not have mattered if the data was originally West (-2) or East (2).
In the end, I'm looking to get useable data on current speed. But I'm not even sure if the end result of this kind of data should be (A) magnitude + direction (ie 2m/s at 20 degrees) or just (B) a single number that is only a combined magnitude with no reference to direction(ie 2m/s). I know for my calculations I do need an absolute magnitude that would represent current speed (option B) but am not sure how to calculate this.