Spline waypoint altitude error

FW 3.4.3


The following picture is the mission Waypoints (dark) and actual (green):

Why is there such an altitude difference between programmed and actual?
I used the “verify height” selection on the initial programming.
Even the logs reported I flew no lower than 100 feet above home but video evidence shows differently.
Especially the 4th spline waypoint where I almost hit some trees because I was much lower than 100 feet.

2016-12-17 15-28-10.bin (3.3 MB)

2016-12-17 KMZ.zip (140.3 KB)

Bumping - No ideas?


I had a look at your log, but no evident clue.

I use to fly Spline navigation (Navio2 with 3.4.3 or VRBrain 5.2 with 3.3.3) without experiencing your problem.

I use Tower (Android) for planning, logic is not the same. You may have a try if you have some android device available.

You could also try to have more waypoints along the differents legs of your flight plan. If the glitch is memory related, having shorter legs could help.

Please feed back,


Tower might be worth a shot.
I have been wanting to try it out.

I will have to get the connector but I will report back ASAP

Tower produced the same error

Usually due to discrepancies in Google’s terrain elevation data. I’ve seen discrepancies of 40-50 feet vs actual survey data supplied by USGS. Combine that with pressure changes due to atmospheric conditions and wind on slopes or terrain features, and its effect on the barometric altimeter, and you can easily fly an aircraft into the ground.

When planning survey flights where the aircraft must fly at a specific height above terrain I ALWAYS use the ArcGIS elevation model from the survey done by USGS, calculate the waypoint altitude myself, and never use Google’s estimation of terrain elevation. Google’s stuff might be “good enough” for the average consumer. But it’s not good enough to fly an aircraft with. If you read Google’s licensing terms on their supplied data, that is clearly stated.

Google has been “good enough” for normal waypoint flying.
It is spline missions I have issues with.

It has always been a steady loss of altitude during spline missions.
Not a sudden loss associated with atmospheric conditions.