Launching for the air

How do I start a mission in the air? Is this possible? I need to do it because I am working in a forest area.

Yes, if you have the current app version it should work. We do not recommend it though.
Launch with the DJI app and go up to altitude keeping the drone in view. The controller should stay connected when you close the DJI app and then open the DD app as the drone hovers. Sometimes it may be necessary to unplug the USB cable from the mobile device and plug it back in to connect the drone between apps. You should hopefully then have enough GPS signal to go through the checklist and fly.

I have also found in wooded areas that first turning on the DJI GO app and letting it get signals on the ground, then going to the DD app on the ground helps connect the GPS. You might try that.

Thanks for the info. My other question is I am working in a mountain area. If my home point is say 100 feet AGL and an area that I have running the mission has a slope that changes to 800 feet AGL how do I adjust for the altitude change in the mission. If I set my altitude to say 200 feet from the home point I am concerned that I will crash into the top of a tree once the drone gets to the area that is at 800 feet AGL? What is the best way to handle this? Thanks again

Terrain following is being tested, but for now it sounds like you safest bet is to split the flight into 2 or 3 pieces. Is your home point in the middle of the flight plan and the rise is from your home 100 feet AGL to 800 AGL, or is the 700ft rise the amount of the entire plan change? I would try to setup the flight plan so that you drone is no more than 300 or 350 from the ground as you will lose allot of detail. Essentially if you start at 100ft (which seems really low) you are capable of a 200-250ft delta in each section.