Number of sat locks needed for reliable guidance?

[Skybuyer]

I use the UAV Forecast app to check the conditions prior to flying. I have one more segment for my project that I want to re-shoot, hopefully tonight. The time, for the light, will be just after 7pm. The Sat lock at 7 is 11.8 satellites and UAVF is saying "not good to fly" at that time, based (I presume) on too few satellites. It appears that 12 satellites is the magic number in this program and at 8pm there will be 13.6 sats in the area. How many satellites are really needed when flying???

I've also become a little gun-shy about higher winds as I'll have to be flying at about 100 feet. Gusts are predicted to be 10mph AGL and I definitely don't want to be blown away in this area as it would be extremely difficult to recover my drone should I lose it. This one shot segment will be the only one I need to get, which I'll do first while the battery is strong. Is there anything to worry about even if the gusts up on the air are 15mph?

 

[lannes]

Enough to set the home point accurately

How many satellites are really needed when flying???

Enough to set the home point accurately

 

[OldEd]

I only fly with a minimum of 10 sats

 

[Skybuyer]

I only fly with a minimum of 10 sats

According to UAVF app it will have almost 12 available. I'll have to get out there and see. Hopefully the wind won't pose any issues as I don't anticipate flying over 100 ft AGL.

 

[azmikew]

If you tap any box on the UAV Forecast screen, you can change the values or options.

 

[Meta4]

The Sat lock at 7 is 11.8 satellites and UAVF is saying "not good to fly" at that time, based (I presume) on too few satellites. It appears that 12 satellites is the magic number in this program and at 8pm there will be 13.6 sats in the area. How many satellites are really needed when flying???

You need a minimum of 6 sats.
But six might not be enough as the sats have to be spread to have good geometry for accurate location data.
UAV Forecast is misleading you as it is only giving you numbers of US GPS sats.
Your drone also receives data from Russian GLONASS sats so you'll have more sats than UAV Forecast says.
In fact, you can just ignore the GPS section of UAV Forecast since wherever you fly, you will always have more than enough sats in the sky as long as your drone has an unobstructed view of most of the sky.

I've also become a little gun-shy about higher winds as I'll have to be flying at about 100 feet. Gusts are predicted to be 10mph AGL

Don't be fooled into thinking that UAV Forecast can tell you what the wind will be when and where you fly.
It's just a forecast and there are plenty of reasons why it might not be accurate.

 

[Skybuyer]

You need a minimum of 6 sats.
But six might not be enough as the sats have to be spread to have good geometry for accurate location data.
UAV Forecast is misleading you as it is only giving you numbers of US GPS sats.
Your drone also receives data from Russian GLONASS sats so you'll have more sats than UAV Forecast says.
In fact, you can just ignore the GPS section of UAV Forecast since wherever you fly, you will always have more than enough sats in the sky as long as your drone has an unobstructed view of most of the sky.

Don't be fooled into thinking that UAV Forecast can tell you what the wind will be when and where you fly.
It's just a forecast and there are plenty of reasons why it might not be accurate.

Great reply. I didn't understand how GLONASS came into play on the Mini or if they were represented in UAVF. However the UAVF does have a toggle to include GLONASS Sats. It also has a toggle for Galileo Sats- which is toggled off by default.

I don't expect it to be accurate as a wind gauge as but it has come in handy as a general guide. Even forumulas of max drone speed vs wind speed are only a rough guestimate. Tonight I was flying in moderate wind reported to gust only 12mph and I could see the Mini was struggling a bit to get through it, but I never felt that it would be in a blow-away situation.

 

[maelstrom]

You need a minimum of 6 sats.

Is this something specific to the DJI drones/app? In theory, a standard GPS receiver only needs 4 satellites for an accurate fix - 3 to determine the user position and the 4th to resolve any timing errors.

 

[Meta4]

Is this something specific to the DJI drones/app? In theory, a standard GPS receiver only needs 4 satellites for an accurate fix - 3 to determine the user position and the 4th to resolve any timing errors.

It's a DJI thing.
I guess they wanted a little more in reserve than the barest minimum.
If you are flying in a constrained area with sat reception is so poor that you can only get 4 sats, you could easily lose one.
But if you are out in the open with an unobstructed skyview, you'll always have plenty more sats than the minimum.

 

[WDKZoom]

If you tap any box on the UAV Forecast screen, you can change the values or options.

The changes I made were temperature 95 degrees, wind 15MPH as well as gust and no less than 7 sats locked.

WDK