GPS problems?

I had a job last week where I was supposed to map about 350 acres, all on very hilly terrain. If the base was at zero elevation, the elevation at the top was well over 1000 ft. I was going to fly at 400 ft. AGL.

I had an issue with getting enough satellites from zero to about 200 ft. Only getting maybe 5-6 satellites in that range. Because of that my GPS wouldn’t lock in on the ground at takeoff.
I ended up manually flying up to around 200 ft and from that point up I was able to get enough satellites and the GPS was on.

My concerns were these: Can you start a DD mission while the drone is already in the air" Will it take off from that point and fly to the starting place? Or fly to the last place it was at, and resume the mission?

Once the drone is up and following the designated flight path, if the mountains ahead block the signal? As I stated, the terrain was very hilly and my fear was that the drone might get into a low spot and have the drone disconnect. And from that point I don’t know if it would continue the flight? Stop the flight? Lose all control and crash?

I appreciate your comments.


Bueller? Bueller? Bueller? :stuck_out_tongue_winking_eye: :smile:

Yes, you can takeoff manually and then start DroneDeploy. We run into the same thing and we’re working downtown. You’re limited to the 30 ft, but once it bakes for a little bit you get enough satellites to start.

You’re limited to the 30 ft?

That’s what happens to a P4P when it doesn’t have a GPS lock.

I’m sorry I don’t understand. Are you saying that if you don’t have enough satellites before you take off for the mission…that you can only go up to 30 ft to try and get more satellites before you can start the DD route plan? As in, if you get up to 30 ft without enough satellites, then you can’t even start the mission?

I appreciate your time, Michael.


It is a DJI limitation. It has nothing to do with DroneDeploy. I think the idea is that if the drone does not have a good GPS lock, then it will not know how to return to home in an emergency.

To see if you can overcome this, you could try starting the mission at another location.


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Hey, Terry…
Thanks for your information. That makes sense. With the scenario I was involved with, starting the mission in a different location wouldn’t have really changed anything, because the overall map could go from zero to somewhere around 1800 ft, with a bunch of hilly terrain between those two elevations. And my locations to take off from where few and far between because of the enormous amount of trees throughout the property.

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That’s correct. It is in the specific scenario though. From what I have read it’s 30 and 90m but I am getting 10m. Once it bakes for a minute I can go. It’s in DJI but backed up by DroneDeploy you have to have 7 good satellites to get past it which normally isn’t even a problem but technically the “good” is the key. You can have 10 satellites showing but 4 of them are dirty and don’t count.

Hi @MavAerial!

MichaelL is correct. You can take off manually by Switching to S mode on your controller and when you reach an altitude where you have enough GPS locks then switch back to P mode on your controller and begin your preflight checklist on DroneDeploy to begin your mission.

To answer your questions. Yes, the drone will take off from that position and fly towards its first waypoint to begin the mission after the preflight checklist. (I would also advise that when the mission is complete you take manual control of the drone and perform the RTH and landing yourself due to the issue in this area and GPS lock)

May you please share a screenshot of your flight plan? I’m thinking we can optimize the planning here and break it up into sections that way you can plan the regions of the terrain that are “hilly” and difficult to fly autonomously better whilst still being able to capture the majority of the site.

Thanks, @MichaelL @SolarBarn for the helpful responses on this! :muscle:

Farai, thank you for your response.
This first map is just a quick rendering showing the entire flight area. The red dots/lines show the couple of spots where I should be able to take off and land from. I missed putting one on the far left edge where those roads are. Other than that, there aren’t to many options there.

I have attached the two portions of the map that I had laid out. I designed it in two stages because of the lack of roads there, and places where I have an open area to bring the drone down, change the battery and launch it again.

As you can see on the maps, there is a lot of elevation difference in this map. Going literally from zero elevation to well over 1000 ft throughout the flight. (Just measured on Google earth and it says the difference is around 1200 ft between the valley and the uppermost peak in the route)

The first map is actually the bottom half of the flight and the second map is the upper half of the flight. The upper half has more acreage, at 178 acres with the bottom having 152 acres. Both upper and lower flights were coordinated for me to be able to take off and land in areas where I can be somewhere close to the little bit of road that goes through there.

I have it set up going from top to bottom, instead of side to side because of the lack of roads or other areas that would be clear enough to take off and land the drone.

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This is a great point. When doing TA on terrain with a lot of relief you should setup your pattern to follow the contours. Along the slope instead of against the slope. This will also reduce the amount of waypoints that are added for changes in elevation.

Do you mean something more like this??

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You had it right the first time, I was just agreeing. Run with the ridge (slope) to minimize the number of gradebreaks.

the most common GPS problems are the following:

  • Wrong installation : An incorrectly installed GPS can lead to inaccurate data. Careful checks during the installation are vital to ensure the right operation of the system.
  • User error : Human errors can happen, such as the GPS being left in dead reckoning (DR) mode.
  • Atmospherics : Satellite signals can be affected by irregular activity in the earth’s atmosphere.
  • Local issues : In some locations, the availability and quality of GPS signals can cause issues. Errors can also be expected when satellite signals hit structures or mountains.
  • Deliberate acts : Jamming, spoofing and hacking can affect the GPS signal.

However, in case of a GPS problem, it is very important for the operator to know how to use traditional methods of fixing a vessel’s position.