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Flight planner and PC Ground Station


I'm a land surveyor and two weeks phantom 2 user. I bought it for mapping purposes.

Today (later an hour of rain), I tested the flight planner, I found very easy map a flight. First time using the PC Ground Station software. After defining all the parameters for flight (phantom 2, go pro 3+ silver, datalink 2.4) in the flight planner:
Area width: 150m Area lenght: 150 m. Altitud: 75m. Speed: 6 m/s

The results with those parameters were:
108 images, 5.11 minutes of flight time, 1.8 km, highest ground point 319.9 meters (it's the highest ground level point in the surveyed area).

The ground level at the site where it tested show 309 meters, and the height of the flight show 392.9 meters. So I thought the resulting altitude was 392.9m - 309m = 83.9 meters were good for testing purposes.

In the GS software, I checked the imported waypoints, everything looks fine, then I made the connection to the phantom via COM3-BLUETOOTH-data link, and uploaded the data and finally press GO.

The phantom dissapear. It tooks a lot of altitude (I think they were 392.9 meters). I hear just a little noise from the propellers. I saw nothing but clouds.

After 6 minutes thinking what to do, I decided to turn off my laptop, and turn off my Remote Control, later (20-30 seconds) the phantom appeared descending straight vertically to the point where I begun the flight.

And the worst of all, I forgot to turn on the gopro.

My questions are:

1.- Why did the phantom took that altitude?.

2.- How can I interpret the altitude obtained (319.,9 meters from the flight planner and the 392.9 meters from the PC GS)?

2a.- Altitude 392.9 it's relative to the ground or sea level?

3.- Did the PC Ground Station only holds 15 way points (at the site, i need to erase 16-18 waypoints)?.

screen captures:


Official comment


It sounds like it was operating in "height mode" instead of "altitude mode" meaning that it was using the ~390 m value as the height above ground instead of the absolute elevation to go to above sea level. You can change this setting by going to the Sys Set menu and going to Altitude Offset. There you can change the mode to elevation instead of height.

We pull the highest elevation along the flight path from Google and add the specified AGL value from the Flight Planner to that.

For example: If you specify a survey area that has a hill that is 100 m taller than where you start but want to fly at 70 m AGL, the flight planner will take that into account and add your 70 m to the top of that 100 m. That is a check the ground station software doesn't do and would let you fly right into the hillside... Thanks DJI!

We will be changing the altitudes to be relative to the takeoff point since "height mode" is the default in the software as of 2/2/2015.

NOTE: This only takes ground level into account. Not trees, buildings or any other structures. Setting the flight altitude too low in the presence of tall objects will result in crashing.

This is where using DJI equipment is pretty nice though. They come back to the start point pretty reliably. Certainly better than a bunch of other systems we have heard about...

For the waypoints: You have to know how many way points your controller will allow you to program. The Phantom 2 is 16. If you use a WooKong, it is 50 and the A2 is 200. You just need to take that into account when laying out your flight. We will maybe be adding an equipment selector in the future, but for now, you have to know your hardware's limitations. The AWM file that gets generated can easily be edited with most text editors. Just trim it so it fits.

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