See your signal shadows with Google Earth

DnA_Pappas · Oct 15, 2017

Not sure if anyone has tried this out. I came across a pretty neat tool in google earth while planning a litchi relative to ground mission.
If you put a place marker on a spot you want to fly to, you can set that place markers altitude to the same altitude your drone will be at when it gets there. Now under the edit menu, click on "show viewshed". That will show you in green the areas your drone can see from it's point of view. Shadowed spots, or spots where your signal will be weaker will be in grey shadows. Move the map to see if you are standing in a shadow because of something between you and your drone. You can change the altitude of your place marker and the open viewshed again to see how many shadows you lose or how they change..
I haven't seen this tool mentioned anywhere and I thought it could be pretty useful. Sorry I'm not better at explaining the procedure on how to do it. If you google search, "how to use viewshed in google earth" you can get a couple of youtube video's that will explain it better.
I live in a hilly area so this works well for my flight planning.
Here's a youtube link

Just remember to exit viewshed and then re open it from the edit menu every time you change your place markers altitude to see the updated changes.

JohnnyB · Oct 15, 2017

Subscribed... Thanks for sharing. Useful tool!!

wa5tef · Oct 15, 2017

Hey DnA, that's a really good post. I'll give it a try next time I program a waypoint or Litchi mission. Google Earth is amazing, and to be free too! I found one feature that let me, as a ham radio operator, set two points and plot the distance, direction, and topography between the two points showing hills and other obstructions that would block a VHF or UHF signal. I can't remember where I found it and I have tried again several times to access it but no luck yet. Maybe someone out there knows it and can advise.

Anyway, thanks for posting that info.
Jim
WA5TEF

Vichian-Bruno · Oct 16, 2017

wa5tef said:
set two points and plot the distance, direction, and topography between the two points showing hills and other obstructions that would block a VHF or UHF signal.

Do you mean "Show Elevation Profile" when you right click on the path created in the "Places window" in GE?

Vichian-Bruno · Oct 16, 2017

@DnA_Pappas

thanks for sharing this information, great tool to check whether the mission is running at "correct" hight to make sure a particular aera will be shown or covered during mission in hilly landscape or to plan so called "revealing shots".

DnA_Pappas · Oct 16, 2017

Vichian-Bruno said:
@DnA_Pappas

thanks for sharing this information, great tool to check whether the mission is running at "correct" hight to make sure a particular aera will be shown or covered during mission in hilly landscape or to plan so called "revealing shots".

That would work perfectly.

DnA_Pappas · Oct 16, 2017

Vichian-Bruno said:
Do you mean "Show Elevation Profile" when you right click on the path created in the "Places window" in GE?

No, I mean "show viewshed" under the edit menu. This only works after you place a pin, or marker at a certain place and height to get a point of view from that point.

DnA_Pappas · Oct 16, 2017

Make believe you are a transmitting antenna. Now, you want to be able to know how many signal shadows are in your coverage area, how big they are, etc. from your place of installation. If you were an antenna installed on a radio tower at a certain location say at 100' in elevation above the ground, you could use this tool to see the shadows from that antennas point of view. You can increase that altitude and then look at the viewshed again to see how many shadows you eliminated. Again, I'm sorry for not being good at explaining this, I just figured I would share it with you all because I'm finding it very useful to find my best control location prior to my flights.

DnA_Pappas · Oct 16, 2017

I placed my drone 1.7 miles away from where I will be controlling it on the map at 350m altitude, shown in first picture. The first picture shows my point of view from the drone to the control point as referenced by the red line. The second shows my signal coverage from the drone in viewshed. Next pictures show 150m altitude and how much my signal coverage is reduced at a lower altitude.

Zoomed pictures of my control point below. First picture shows drone at 350m and second shows how much different it is at 150m.

Now before anyone gets on their self righteous band wagon about how high I am flying, I am not. This is for illustration purposes only. It just shows how much more altitude I would need to start overcoming the shadows that I have at a lower altitude.
Green = No Shadow
Grey/Black = Shadowed
You can see in the 3rd picture that if I move a few feet to my left with the controller, I would be in a "line of sight" position from the drone. At only 1.7 miles away, I should have a full signal strength for video and control, not accounting for any local interference.
The 4th picture shows if the drone is only at 150m altitude, I completely lose my "line of sight" because of obstructions between me and the drone.
This tool works for ground elevation changes (hills), buildings and structures, trees although accuracy for trees will depend on how old the pictures are and how much growth they had since the pictures were taken.

wa5tef · Oct 16, 2017

Pappa’s, that is very interesting!! I can’t wait to try it. Google Earth is amazing with all its features and it is free too. Thanks again for revealing this feature to us and thanks for your work with the examples

Jim
WA5TEF

Poolz · Oct 16, 2017

Thanks for sharing this

DnA_Pappas · Oct 16, 2017

Just an update, after further testing I am finding that it doesn't shadow tall buildings when you are next to one at a low altitude, say about 10 feet. Not sure if it works at distances or higher elevations though. So far, all I see is elevation shadows, eg. hills, mountains. I will update as I discover more. And just another note, I am using Google Earth Pro. Not sure if that makes a difference on the free version or not.

wa5tef · Oct 16, 2017

Pappas, I just tried that on my desktop computer for reference. It is amazing to be able to see what areas are shadowed from the drone's signal at different heights! I'm going to play around with it more and get familiar with it. I' sending it to my son in Georgia who flies a Mavic. He'll love it!
Thanks again for this information!!!
Jim
WA5TEF

Mark The Droner · Oct 17, 2017

Just tried it. Very nice! Thing is, it doesn't account for trees. Also, since we don't fly at ground level, not sure how relevant this is. It would be better to anchor it at the AC's desired location, say 120 meters up from a particular point, then see if the shadow is cast at the spot where the controller would be. Does this make sense?

DnA_Pappas · Oct 17, 2017

Mark The Droner said:
Just tried it. Very nice! Thing is, it doesn't account for trees. Also, since we don't fly at ground level, not sure how relevant this is. It would be better to anchor it at the AC's desired location, say 120 meters up from a particular point, then see if the shadow is cast at the spot where the controller would be. Does this make sense?

When you place your pin or placemark, in the properties you can set the elevation of that pushpin in the settings for it. Go to the altitude tab, change the drop down menu to "relative to ground" then set the altitude you want your pushpin to be at. Now you can see from that point and it's set altitude it's point of view from the air.

DnA_Pappas · Oct 17, 2017

Mark The Droner said:
Just tried it. Very nice! Thing is, it doesn't account for trees. Also, since we don't fly at ground level, not sure how relevant this is. It would be better to anchor it at the AC's desired location, say 120 meters up from a particular point, then see if the shadow is cast at the spot where the controller would be. Does this make sense?

Look at my photos above. They are showing exactly what you are wanting to do. One picture shows a high altitude and the shadows from that height, and another picture shows a lower altitude and how much the shadows change at a lower height.

DnA_Pappas · Oct 17, 2017

wa5tef said:
Pappas, I just tried that on my desktop computer for reference. It is amazing to be able to see what areas are shadowed from the drone's signal at different heights! I'm going to play around with it more and get familiar with it. I' sending it to my son in Georgia who flies a Mavic. He'll love it!
Thanks again for this information!!!
Jim
WA5TEF

Now, how can we build a signal repeater for the control and video? ;-)

DnA_Pappas · Oct 17, 2017

Mark The Droner said:
Just tried it. Very nice! Thing is, it doesn't account for trees. Also, since we don't fly at ground level, not sure how relevant this is. It would be better to anchor it at the AC's desired location, say 120 meters up from a particular point, then see if the shadow is cast at the spot where the controller would be. Does this make sense?

The bottom 2 pictures show my controller location at the end of the red line. First bottom picture shows shadows when the drone is at 350m and the second is at 150m. Big difference in shadows and the only thing I changed was altitude of my pushpin.

Nick Mendocino · Oct 21, 2017

There's another free app called www.heywhatsthat.com that plots viewsheds and IDs mountain peaks. A local wireless ISP uses it for planning repeater sites and analyzing signal paths. It's originally for mountaineering and hiking to see what's that peak you see in the distance, hence the name However they have done further specialized development to cater to wireless ISPs. It allows you to set the height of the tower (or drone) at each end of a signal path.