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Estimating object (buildings, power lines) height

1dr1

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How do you estimate the height of objects, like buildings, power line poles, and signs?

You can use trig calculations based on the angle from eye level to the top of the object, but that requires knowing the horizontal distance from where you are standing to the base of the object. It might not be easy to get the base distance, unless you use a range finder.

Any ideas ?
 
Ascend directly above the takeoff point and yaw 360 degrees to ensure there are no obstacles in sight. If you see any obstacles, keep ascending until there are none in sight. Then, set your RTH altitude to your current altitude plus 50 feet to add a buffer since the altitude is only an estimate.
 
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Ascend directly above the takeoff point and yaw 360 degrees to ensure there are no obstacles in sight. If you see any obstacles, keep ascending until there are none in sight. Then, set your RTH altitude to your current altitude plus 50 feet to add a buffer since the altitude is only an estimate.

....while keeping the gimbal level (all the way up), so center of camera equates to position of Mavic.
 
Found a great tool for determining object heights.....Hivemapper.com, right now only for Android, but object heights can be determined before flying on a PC. The app shows building, powerline and antenna heights. Check it out Hivemapper | 3D map for drone fliers
 
I have tried the trig range finders. Unfortunately, distance or relative height from YOU to OBJECT'S BASE is not always obvious even on a good Google Map aerial/satellite shot. This throws off height calculation.

Most accurate I have found is to ascend from a clear starting point anywhere within sight of the target object, with gimbal level forward. When the target object's top matches the horizon, the aircraft height matches the target object's height. (Sphere horizon, not apparent horizon, in case of distant hills.)

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I find it's worth using half a battery or more to scope out all your obstacles if you're planning to fly close to them. Just raise straight up, jot down all the data you need, and land again to set up your safe RTH altitude for a more complex mission on the next battery.
 
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Great thing about Hivemapper is that there is a topo overlay on the map, so you can find the elevation of your home point and can find the elevation of objects near your home point. There is also a filter to highlight objects at the height you plan to fly.
 
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A sectional map will have heights of tallest objects in the area. There are app versions of these. also- maybe less precise, but if you have google maps and gps coordinates, Smart Tools for iOS/Android will let you calc the angles.

Good luck!
 
I have asked the Litchi team to add support for a third type of pin; waypoint, point of interest, and a new HAZARD (X) pin. My area has a lot of high-tension power lines which can be difficult to see on satellite photos when planning a mission. I want to put a few reminder markers into my mission so I don't tweak a flight path right across an object I have forgotten.
 

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