In reference to the example on the linked page, I assume the waypoints are specified in the waypoint trajectory reference frame. So the waypoint at [10 50 10] specifies a waypoint at 10 m down if in NED and 10 m up in ENU. In either case, the trajectory starts at 0 and moves to positive 10. When using plot3, the default direction of the z-axis is to point up on the screen, so even a motion from 0 to 10 m Down looks like the trajectory is going up on the screen (and likewise the East axis looks like it's pointing west).
waypoints = [0 0 0;
10 50 10];
speeds = [0 10];
jerkLimit = 0.5;
trajectory = waypointTrajectory(waypoints,GroundSpeed=speeds,JerkLimit=jerkLimit,ReferenceFrame="NED");
t0 = trajectory.TimeOfArrival(1);
tf = trajectory.TimeOfArrival(end);
sampleTimes = linspace(t0,tf,100);
[position,~,velocity,acceleration,~] = lookupPose(trajectory,sampleTimes);
figure()
plot3(position(:,1),position(:,2),position(:,3))
xlabel("N (m)")
ylabel("E (m)")
zlabel("D (m)")
title("Trajectory")
It's probably possible to muck around with the axis properties to make the axes look closer to physical reality. Alternatively, plot in ENU even when the data in NED.
