How good is Google Earth Pro for ground elevation changes?

[modbuilder]

I'm using Lat/Long on Google Earth Pro to create an initial waypoint path that uses an altitude relative to ground. Then pulling that kml file into Litchi to finish the mission planning. I find I'm surprised at how much ground elevation changes appear in the resulting path in a tract of land that otherwise appears fairly flat, but then you can't see very far into the woods and the aerial views are hard to judge ground elevation changes.

My concern is that many of my video missions are flown with only about a 50-foot vertical clearance above the tree tops. If I can rely on the accuracy of Google Earth Pro to know the ground elevation changes, I'm OKAY. If its precision is pretty large, I should give myself more clearance.

Anyone have first hand experience/knowledge with ground elevation accuracy in Google Earth Pro?

 

[lisadoc]

Here's a scientific article that studied that exact question:

Google Earth elevation data extraction and accuracy assessment for transportation applications
(Google Earth elevation data extraction and accuracy assessment for transportation applications)

Bottom line summary:

1. The accuracy of elevation data from GE is better along roadways compared to other elevation data sources in the conterminous USA, with MAE, RMSE, and GE roadway elevation error standard deviation of 1.32m,2.27m and 2.27m respectively;
2. Google Earth elevation data is a valuable resource for transportation applications. The precision of GE elevation data along roadways is satisfactory, and there is no evidence showing the accuracy of GE roadway elevation varies significantly between states or route types;

 

[BD0G]

Here is a helpful thread to allow one to prefly thier Lichti Missions within Google Earth. There is a new tool that allows the Mission to be imported into Google Earth and preflown. Keep in mind Google Earth is not so good with tree elevations. I preflew a Lichti Mission that had me clearing trees in my area by a good number of feet. Flew the actual mission while observing the camera pointed straight ahead. There were multiple trees that I would have smacked into as shown on the front view of the camera. Adjusted elevations again in Lichti Mission Hub and flew again without any potential obstructions.

Virtual Litchi Mission

 

[modbuilder]

Got to +1 BD0G's post and comment on LisaDoc's post. The scientific study linked above found that GEPro was plenty accurate for my purposes. The caveat is that the study was done for road elevations, not terrain elevations out in the woods.

I flew a Litchi mission on a 100-acre wooded lot Tuesday that I'd set up in GEPro, fine tuned in Litchi, and did the Virtual Litchi Mission tour on GEPro. All looked good in the virtual mission. Ran the actual mission with the Mavic Pro looking into the interior POI's, so of course it was flying sideways. I got into a section of the mission where the camera was looking more or less toward the next WP, and lo-and-behold there's a dang tree approaching at my height that should have been 60 feet below. I paused the Litchi mission, took control, and hand flew it to safety. When I re-looked at GEPro's terrain elevations later, not only was GEPro waay off on the terrain elevation relative to WP#1 at the point (in the woods) where I interrupted the mission, but that point was actually shown as one of the lower terrain elevations in the mission.

I still use the same process for setting up missions, but now I'm running the first actual mission in the field with the drone looking toward the next WP so I can see what's approaching. Once I'm satisfied that I have a safe mission to fly, I run a second one with the POI's that I need and let it fly sideways all it wants.

BTW Guys and Gals -- that Virtual Litchi Mission link that BD0G posted above is to a remarkable goodie if you're into flying autonomous missions. Thanks a ton for that info BD0G.

 

[BD0G]

Been there and done that! Tree was right in my path where it should not be.

 

[lisadoc]

Terrain doesn't move or grow. Trees, unfortunately, don't stay the same height. Google maps terrain, not vegetation. The OP asked about the accuracy of ground elevations, not trees.

 

[modbuilder]

I haven't found that trees in the Carolinas vary much in max height. I haven't found any more than 100ft tall. So when I'm flying at 160 AGL, and suddenly a tree top appears in front of me, it's the terrain having changed, not a tree having grown.

 

[modbuilder]

Not saying the terrain changes from one time to the next. Am saying that GEPro isn't as accurate in the woods as it is on roadways. Take it or leave it.

 

[BD0G]

Terrain doesn't move or grow. Trees, unfortunately, don't stay the same height. Google maps terrain, not vegetation. The OP asked about the accuracy of ground elevations, not trees.

We splitting hairs here. It is important to not rely on Google Earth's representation for Tree Elevations as that is what will get most flyers as they are not typically not flying at ground strafing low level altitudes using a planned Lichti Mission.