# VMT_VelVectMagDir

## PURPOSE

Computes the magnitude and direction of velocity vectors given the east

## SYNOPSIS

function [xo,yo,mag,dir] = VMT_VelVectMagDir(xi,yi,Veast,Vnorth)

## DESCRIPTION

     Computes the magnitude and direction of velocity vectors given the east
     velocity and north velocity at specified points.  Positions x and y of
     the observations are passed through.

     P.R. Jackson, USGS, 1-15-09

## CROSS-REFERENCE INFORMATION

This function calls:

This function is called by:

## SOURCE CODE

    0001 function [xo,yo,mag,dir] = VMT_VelVectMagDir(xi,yi,Veast,Vnorth)
    0002 % Computes the magnitude and direction of velocity vectors given the east
    0003 % velocity and north velocity at specified points.  Positions x and y of
    0004 % the observations are passed through.
    0005 %
    0006 % P.R. Jackson, USGS, 1-15-09
    0007
    0008 %Compute the magnitude
    0009
    0010 mag = sqrt(Veast.^2 + Vnorth.^2);
    0011
    0012 %Determine the quadrant
    0013 indx1 = find(Veast >= 0 & Vnorth >= 0);
    0014 indx2 = find(Veast >= 0 & Vnorth <= 0);
    0015 indx3 = find(Veast <= 0 & Vnorth <= 0);
    0016 indx4 = find(Veast <= 0 & Vnorth >= 0);
    0017
    0018 %Compute the direction in degrees from north (+CW)
    0019 dir = zeros(size(Veast));
    0020
    0021 dir(indx1) = 90    - atand(abs(Vnorth(indx1)./Veast(indx1)));
    0022 dir(indx2) = 180   - atand(abs(Veast(indx2)./Vnorth(indx2)));
    0023 dir(indx3) = 270   - atand(abs(Vnorth(indx3)./Veast(indx3)));
    0024 dir(indx4) = 360   - atand(abs(Veast(indx4)./Vnorth(indx4)));
    0025
    0026 %Pass position through
    0027
    0028 xo = xi;
    0029 yo = yi;