How many satellites are there to hook up with?

[BigAl07]

How I started

"Not a mavic pilot but a new Bwinef7 flyer interested. Can I jump in?
---

Athough you are not flying a DJI Drone, many of our members are also flying non-DJI drones and you might find some with your drone here. I hope we fill your expectations and don't be afraid to contribute the discourse…

I appreciate the welcome. I have my FAA small cert of registration.
The F7 is 550 g.
Totally new at flying with only 2 batteries of time in the air. Excited to see the possibilities. Nervous has a new meaning. It has no avoidance but I feel it was a good place to start. I was a pro wedding photographer until I fell off a 90 ft cliff. This gets me back in the game from ground level for my internal titanium parts lol."

I will continue to only lurk as to not confuse the group. My bad.

Listen, I never meant you "couldn't" jump in and participate but making sure you (and others trying to help you) realize the advice given on this forum might be DJI specific, is well worth the odds of possibly hurting your feelings. I'd much rather you get your feelings hurt rather than taking advice that was given incorrectly (by mistake ) and you having some type of incident.

Please feel free to post if you are so inclined.

 

[Thomas Argo]

I've been aware of that since post #5 and addressed the OP accordingly.
My post #17 was in response to post #15 from a DJI user talking about his DJI drone.

Thanks Meta4. I showed up to ask how the sky works for drones in general never asking about mine. I have learned a lot here so far. The biggest being the legal aspects of where a drone can be flown. I ordered a strobe for my night flights only because I read about it here.

 

[Red Pyro]

Bwine f7gb2 back with a question. I am in Pennsylvania Hanover twp zip 18706.
My app lists sat connections. I noticed numbers from 8 to in the 20's. The numbers change quickly.
Are things better at 20 than 10? Is there a max? I did not even know what the small number was an hour ago.

Depends how many use Tinder

 

[JohnnyComeLatly]

Just a few comments, as a former US Air Force GPS satellite operator. Your number of satellites is changing because the satellites are orbiting at a 12 hour interval. Meaning, they rotate around the Earth once every 12 hours, or twice per day. They're at a 55-63 degree inclination (relative to the equator) so your best reception is always closer to the the middle of the Earth, and the least at the North and South poles. Usually not a problem for most users.

GPS was fully operational in the mid 90s (when I was there) and then other countries launched their own versions. Russia has GLONASS, and most "near-peers" of the US also have their own versions. Your receivers will try to lock on as many as in view, see above, as they can be in view for minutes or a lot longer. The key is for it to get the widest dispersion of satellites, as this gives the best reading. If you're a math/trigonometry geek, google and read about "geometric dilution of precision," (GDOP) as this explains how your GPS receiver is triangulating* your position. Closer satellites (relative to each other) give a worse GDOP, and more dispersed satellites give you a better GDOP. In layman's terms, the most precise position of you, or your drone.

GPS is pretty low energy RF, and its antennae disperses the signal across the entire face of the Earth, and so cloud cover or being indoors is going to influence your reception. To a smaller degree, troposphere and other RF interference will also cause reception issues.

* Triangulating because what a GPS satellite is transmitting is ITS point in space, and a time hack. We know RF travels around the speed of light, or 299M meters per second, and then the time you received it. By subtracting the reception time, from transmission time, and dividing by the speed of light, you have one "pseudo range." Now do this multiple times for multiple satellites. You will triangulate to TWO spots. One on the face of the earth, and another about 23,000 miles out in space. If you were a satellite, this would then require some complicated math to drop the wrong one. If you're terrestrial, then it's obviously not the one in space. Low Earth Orbit satellites are also starting to use GPS/Gallileo/Etc to determine their points in space, so this isn't a theoretical example any more.

The more triangulations, the more precise your fix is. And, it's called a pseudo range because it's not an ACTUAL measurement, but a mathematical estimation. The troposphere and atmospheric/local RF conditions will slightly skew the measurement, and this is partly why the GPS signal includes something called an "almanac." The almanac gives sophisticated GPS receivers more information on how to precisely measure the pseudo range calculation, as well as the overall GPS constellation health. For example, after a GPS satellite has orbital maneuvers it may take it a bit of time to "calm down," in modeling its position in space. It you REALLY want to be a math geek, read about Kalman Filters and GPS; https://gge.ext.unb.ca/Resources/gpsworld.september97.pdf

 

[Meta4]

GPS is pretty low energy RF, and its antennae disperses the signal across the entire face of the Earth, and so cloud cover or being indoors is going to influence your reception.

Cloud cover?
Tree cover - yes, but cloud cover has never caused GPS reception issues for me in 20+ years using GPS.

 

[Oldwest2]

Just a few comments, as a former US Air Force GPS satellite operator. Your number of satellites is changing because the satellites are orbiting at a 12 hour interval. Meaning, they rotate around the Earth once every 12 hours, or twice per day. They're at a 55-63 degree inclination (relative to the equator) so your best reception is always closer to the the middle of the Earth, and the least at the North and South poles. Usually not a problem for most users.

GPS was fully operational in the mid 90s (when I was there) and then other countries launched their own versions. Russia has GLONASS, and most "near-peers" of the US also have their own versions. Your receivers will try to lock on as many as in view, see above, as they can be in view for minutes or a lot longer. The key is for it to get the widest dispersion of satellites, as this gives the best reading. If you're a math/trigonometry geek, google and read about "geometric dilution of precision," (GDOP) as this explains how your GPS receiver is triangulating* your position. Closer satellites (relative to each other) give a worse GDOP, and more dispersed satellites give you a better GDOP. In layman's terms, the most precise position of you, or your drone.

GPS is pretty low energy RF, and its antennae disperses the signal across the entire face of the Earth, and so cloud cover or being indoors is going to influence your reception. To a smaller degree, troposphere and other RF interference will also cause reception issues.

* Triangulating because what a GPS satellite is transmitting is ITS point in space, and a time hack. We know RF travels around the speed of light, or 299M meters per second, and then the time you received it. By subtracting the reception time, from transmission time, and dividing by the speed of light, you have one "pseudo range." Now do this multiple times for multiple satellites. You will triangulate to TWO spots. One on the face of the earth, and another about 23,000 miles out in space. If you were a satellite, this would then require some complicated math to drop the wrong one. If you're terrestrial, then it's obviously not the one in space. Low Earth Orbit satellites are also starting to use GPS/Gallileo/Etc to determine their points in space, so this isn't a theoretical example any more.

The more triangulations, the more precise your fix is. And, it's called a pseudo range because it's not an ACTUAL measurement, but a mathematical estimation. The troposphere and atmospheric/local RF conditions will slightly skew the measurement, and this is partly why the GPS signal includes something called an "almanac." The almanac gives sophisticated GPS receivers more information on how to precisely measure the pseudo range calculation, as well as the overall GPS constellation health. For example, after a GPS satellite has orbital maneuvers it may take it a bit of time to "calm down," in modeling its position in space. It you REALLY want to be a math geek, read about Kalman Filters and GPS; https://gge.ext.unb.ca/Resources/gpsworld.september97.pdf

I was a land surveyor for 44 years and this explanation is absolutely spot on.

 

[Thomas Argo]

Just a few comments, as a former US Air Force GPS satellite operator. Your number of satellites is changing because the satellites are orbiting at a 12 hour interval. Meaning, they rotate around the Earth once every 12 hours, or twice per day. They're at a 55-63 degree inclination (relative to the equator) so your best reception is always closer to the the middle of the Earth, and the least at the North and South poles. Usually not a problem for most users.

GPS was fully operational in the mid 90s (when I was there) and then other countries launched their own versions. Russia has GLONASS, and most "near-peers" of the US also have their own versions. Your receivers will try to lock on as many as in view, see above, as they can be in view for minutes or a lot longer. The key is for it to get the widest dispersion of satellites, as this gives the best reading. If you're a math/trigonometry geek, google and read about "geometric dilution of precision," (GDOP) as this explains how your GPS receiver is triangulating* your position. Closer satellites (relative to each other) give a worse GDOP, and more dispersed satellites give you a better GDOP. In layman's terms, the most precise position of you, or your drone.

GPS is pretty low energy RF, and its antennae disperses the signal across the entire face of the Earth, and so cloud cover or being indoors is going to influence your reception. To a smaller degree, troposphere and other RF interference will also cause reception issues.

* Triangulating because what a GPS satellite is transmitting is ITS point in space, and a time hack. We know RF travels around the speed of light, or 299M meters per second, and then the time you received it. By subtracting the reception time, from transmission time, and dividing by the speed of light, you have one "pseudo range." Now do this multiple times for multiple satellites. You will triangulate to TWO spots. One on the face of the earth, and another about 23,000 miles out in space. If you were a satellite, this would then require some complicated math to drop the wrong one. If you're terrestrial, then it's obviously not the one in space. Low Earth Orbit satellites are also starting to use GPS/Gallileo/Etc to determine their points in space, so this isn't a theoretical example any more.

The more triangulations, the more precise your fix is. And, it's called a pseudo range because it's not an ACTUAL measurement, but a mathematical estimation. The troposphere and atmospheric/local RF conditions will slightly skew the measurement, and this is partly why the GPS signal includes something called an "almanac." The almanac gives sophisticated GPS receivers more information on how to precisely measure the pseudo range calculation, as well as the overall GPS constellation health. For example, after a GPS satellite has orbital maneuvers it may take it a bit of time to "calm down," in modeling its position in space. It you REALLY want to be a math geek, read about Kalman Filters and GPS; https://gge.ext.unb.ca/Resources/gpsworld.september97.pdf

Thanks JCL. I downloaded the suggested read and it confirms I am not a total geek.

 

[JohnnyComeLatly]

Thanks JCL. I downloaded the suggested read and it confirms I am not a total geek.

Ha! Well if you need any sleepy time material, you got one more source of snooze material.

The reason I'm more familiar with this math model is it's what GPS Control Segment uses to update the satellites. There's a number of monitoring stations around the world (Diego Garcia, Cape Canaveral, Ascension Islands, Thule Greenland, etc) that 24/7 receive GPS. Obviously we know precisely where those stations are, and so by using those same PR (pseudo ranges), it allows a collection of drift data. The Kalman filter at the 2 SOPS, Schreiver AFB is taking all that data, and then when a satellite goes outside an "allowable" amount of drift, the Satellite Operator (SSO, which is what I was) can go up and update the Navigation payload on the satellite. The Kalman filter is what creates that Navigation Payload.

Also, the monitoring stations allow the engineering shop do long term trending on the atomic clocks on the satellites (Cesium and Rubidium last I paid attention). When an atomic clock gets outside the normal allowable, long-term drift, the satellite will switch to another atomic clock for its timing source.

This is why you can use GPS as an Atomic Clock back up timing source, as there's literally 24 sets of atomic clocks in space. It's usually the electrical systems that fail first on old satellites. Eventually the batteries have a hard time holding voltage during a lunar or earth eclipse (when the GPS satellite is in the Earth or Moons shadow).

The precise time they freely give the world is why we can have 400-800G per second datacenter connectivity around the world with little problems...

Or, have a really, really, really precise time hack of when we flew our drone

 

[FlySkyJumper]

Thanks. Is 30 better than 10? New flyer, first drone ever with about 20 flights, all practice.
I did grab some decent cloudy sunsets. No dgi though. It is a Bwine.

Generslly speak, Yes, the more satellites your drone is connected to the better the stability and operation is.

However if you're numbers are in the white you're good to go and can't really notice a huge difference. If your satellite signals are in the red you're stuck at 100 ft agl until 1-3 types of satellites (depending on your drone type) are connected and showing white. For safe flight and operation.

 

[davidarmenb]

Generslly speak, Yes, the more satellites your drone is connected to the better the stability and operation is.

However if your numbers are in the white you're good to go and can't really notice a huge difference. If your satellite signals are in the red you're stuck at 100 ft agl until 1-3 types of satellites (depending on your drone type) are connected and showing white. For safe flight and operation.

That is why the color matters more than the number. You can be connected to 20 gps sats and still be in the yellow because those satellites’ positions in space matter more than their number. If those 20 sats are relatively closer to each other, the calculation for your drone’s position and altitude will not be as precise as if the satellites were farther away from each other in their medium earth orbits (MEOs). JohnnyComeLatly’s post describes this clearly.
I believe this is why you can have ~10 sats and have the indicator be white and good to go but another time you can have ~20 sats and still be in the yellow, waiting for more, or better positioned sats to establish connection with the drone.

 

[Thomas Argo]

Thanks for the continued support. Batteries charging...