RTH Help

[JDawg]

From my experience and from seeing new members lose their bird needlessly the most import preflight setting is RTH. I live in a hilly area and had an unscientific way of setting my RTH height. Messing around with Google Earth yesterday I found you can set it up to give you elevations not only of the land but of the top of trees. Put the cursor over your starting point to get the elevation and then move your cursor over the highest land area or the top of the highest tree and in the bottome right you will see the elevation you actually need to clear. It is actually fun to play with and I found my RTH point was about 20' lower than it needed to be to clear the highest tree in my area..
Google Earth

 

[kadras]

Nice find, thanks. I typically use Google Earth (computer) in 2D mode and never use Google Earth (web), which requires using Chrome so had not noticed this. After reading your post I found that GE/computer has this feature if you're in 3D mode, and tried GE/web. Being able to see the elevation difference between a tree top and adjacent ground worked at my house, but not where I typically fly.

The ability to find the pinpoint elevations is dependent on being in an area where Google is using high-resolution terrain models (generally lidar). Home has had lidar terrain models since 2013, but where I've been flying just got the hi-res data this past year. Google hasn't updated their models in this area yet, so a tree and surrounding ground show the same elevation. "Bare earth" lidar models, in which the trees and other above ground features are removed, are detailed enough to show trails and rocks that trees obscure. The above ground models, which Google is using, can even show elevations of power poles and lines, which it does near me. The usual caveats apply. Though the Google elevation data are precise (1 m resolution), accuracy (actual location vertical and horizontal) can vary (has a tolerance), so leave a safety margin above and around the elevation points.

 

[Jackcutrone]

Wow. Good to know