Dr. Acula
lvl.2
Offline
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How to set altitude at all, or how high to set the altitude?
The altitude it is the first parameter when you tap on a waypoint in the Litchi app or at http://flylitchi.com/hub
How high to set waypoints? I use Google Earth Pro (Pro version is free now.) Move your mouse pointer around your mission area and watch the altitude reading in the lower right of Google Earth. I like to start my flights from a large clearing that is higher than the surrounding area if possible.
Google Earth Pro has a measure tool that can measure a line or path, and show you an elevation profile along that path. That is an easy way to see the highest points on your flight path. Remember that for the Phantom, altitude is 0 at takeoff point, and everything else will be referenced from that 0-altitude point. For example, assuming no objects in the way, if you are taking off at 300' and the highest terrain you are flying over is 375', then the difference is 75' and that is a starting point for waypoint height. Of course you DON'T want to fly at exactly 75' in that example, that is cutting it way too close, I would add 50' or even 100' the first time flying a mission, thus making the waypoint 175' or so (terrain height above takeoff point, plus 100' margin of error.) Way better flying too high than too low!
You also have to account for objects. Trees can be 100' or more, power lines can be 75-100'. Towers can easily be 100' to 300'. Either avoid objects entirely or if you want to fly above them set the waypoint heights way more than high enough above the highest terrain you will be flying over PLUS the highest object on that terrain, like +100 feet higher than you think. So if your 75' taller-than-takeoff-point terrain had a 75' tall tree on it, I would be setting my waypoints at least 250' (75' terrain + 75' tree + 100' margin of error.) Then upon successful mission completion I can review the video and set the waypoints lower if desired/possible.
Keep in mind that the Phantom will fly a vertically diagonal line between waypoints, so if the Phantom is 25' away and 50' above the ground from some 100' tall trees and the next waypoint is at 125' above those trees, your Phantom will probably hit the trees as it diagonally ascends to the waypoint above the trees.
I design my missions with a good manual takeoff point in mind, in a clearing. Wherever the Phantom takes off from is "home" and is 0 altitude. I like to keep my first waypoint and next-to-last waypoints high and in the clear near my takeoff point, not above anything. Then the last waypoint can descend more or less straight down to ~25' near your takeoff point. where you can manually land or hand-catch it. I like to just descend into a stable hover ~5 feet high and hand-catch it with my right hand and use my left hand to cut the throttle for 3 seconds which cuts the engines off. No worries about tipping over or the blades hitting anything that way. So my waypoint heights on a 5-waypoint flight might be 200, 200, 200, 200 200, 200, 200, 25. The first 200 waypoint is above where I am launching and gets me up to a sufficient height, it isn't really part of the mission. The last 200 waypoint is also not part of the mission and brings me back above my launch point. Then the 25 foot waypoint brings it back down to a hover where I can decide what to do next.
If something goes wrong during a Litchi waypoint mission and you hopefully still have good signal and GPS, remember you can move the mode switch on your controller to "P" and the Phantom will stop and hover. Then you can increase altitude as needed and fly it home manually.
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