I am planning a mission. The landing point is not the same location as the takeoff point.

• How can i calculate the distance of my mission ? (Mission planner automatically appears to draw a return to start point as a waypoint - so the distance does not reflect my actual mission distance - sinnce my starting point will not be the same as my landing point)
• Does verify Alt work - I am using APM 2.6 (i.e not PIXhawk) with its latest available firmware. - Do i have to check that value before i start adding waypoints or can i just check it after i have my waypoints saved ?