How to plot error ellipses on the head of the quiver's arrows?

Hi everyone I have some GPS data and I want to plot them as arrows with an ellipse on the head showing the velocities'uncertainty. You can see an example in the image attached. So my dataset is made of six coloumns: latitude, longitude, horizontal velocity, vertical velocity, horizontal uncertainty and vertical uncertainty. I think I can do it if I know the coordinates of the top of the arrows that I can trace with quiver. Do you know how to find these points?

The other problems is that arrows'length in quiver are scaled each other so in order to draw my error-ellipses I need to know the scale factor or at least the length of the arrow in order to scale my uncertainties. Any suggestions?

Answer 1

[darova]

• So my dataset is made of six coloumns: latitude, longitude, horizontal velocity, vertical velocity, horizontal uncertainty and vertical uncertainty.

If scaling of quiver is 1

endx = latitude+hor_velocity;
endy = longitude+ver_velocity;

THen just use for loop to draw each ellipse