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Flight planning tools for maintaining VLOS

Aug 21, 2016
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...Wanted to share some things I learned recently. So I have this very ambitious flight plan:


So while this flightplan is for a high-speed run (80 km/h) with a Parrot Disco, this applies just as much to DJI Inspire VLOS flight planning in areas with trees or buildings as potential VLOS obstructions. Now the biggest problem here is that large stand of trees in the middle, plus some of the buildings between me and my flight path as I approach the bridge at top center. I was scratching my head how to do this, until I remembered that the USGS had lots of SLR (side looking radar) data. As it turned out, they have something even better: LIDAR. So here's how you can verify your proposed altitudes and position will maintain VLOS. First find and download the LIDAR set for your flight area from the USGS EROS site. You'll get one or more .LAS files.

Next, download a free tool called FugroViewer. This will allow you to view and measure things with LIDAR datasets.

Fire up the viewer ,open the .LAS file, and you'll get something like this.


Now, I've added little red pins roughly corresponding to my proposed flight path. Now hit the 3D button:


Now you have a 3D projection you can navigate around.

Next,. I use the "runway" looking icon next to the 3D button to draw a box around the takeoff point to the 2nd leg of the flight:


Now, something kind of neat happens up at top right. I can see all of the trees in actual feet, so I can move my cursor around up there (screen cap doesn't capture this too well), and I can get an exact altitude I need to comfortably maintain line of sight!

So for example, here are a couple/three of the touchiest areas of this flight:


At this point I have to be 684 MSL (river is at 415) for an AGL of 269 feet. Another trickly spot:


The stand of trees is really impinging so I have to climb to at least 761-415 = 346 feet.

The next legs are pretty much the same; about 350 feet. Next, what I was unsure about was the return approach:


Actually it turns out just because of the tree height it's less of a problem than I thought, I just have to set up for final approach at about 285 feet before my final descent.

Hope you guys find this combination of tools useful for your flight planning!

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Reactions: DesertWindAero

Whoops... Sorry. I'm serving these out of my DC, and was using this particular server for some heavy-duty rendering... it caused the webserver process to **** the bed. Should be back up and happy now. I need Nagios or something on this crazy thing...
I have a special tool for VLOS. They are called eyes. If I can't see my airframe, I'm beyond VLOS...

Yes, but with an ambitious flight like this, flying average 80 km/h, it's nice to ensure that you can keep VLOS or at least where you need to place additional visual observers on two-way-radio comms before-hand. Not for nothing, if you want to fly a state or national park, they would need this kind of elaborate info to approve your request.
Thanks for the img's,
impressive tool for a good flight prep. How up to date are those tree heights...
I would certainly do a pre-site survey and do a short vertical-up to check for the highest tree; to set the Smart RTH.
My observer(s) keep the VLOS when it gets critical and i concentrate more on the flite path on iPad.
Yes, agreed. The LIDAR data is from 2012, and trees do tend to grow... actually was considering using DroneDeploy using the Inspire to get a very fine-point survey of the area in .LAS format prior to the main flight, for exactly that reason... But even a simple vertical ascent with the gimbal leveled would be a good verification point, as you stated.

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