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Old 30-06-2020, 19:38   #1
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Suddenly Strong, Many GPS Signals

For some reason my little puck GPS receiver is reporting 15-18 satellites in use for a fix with SNR values above 40db. This from the GSV and GSA sentences received from the receiver. i noticed this a few days ago. Previously I was lucky to have 5 satellites in use for the fix with SNR values around 15DB. Nothing, I am aware of, has changed in the interim.
Here is a screen capture of software I wrote which displays the satellites. 10 GPS satellites and 8 Glonass satellites. Never saw this in the past. Anyone else having the same experience or have an explanation.
https://www.screencast.com/t/jZAmR2E8riy
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Old 30-06-2020, 20:26   #2
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Re: Suddenly Strong, Many GPS Signals

Depends on where you're at. Russian satellites aren't world wide yet, mostly in the northern latitudes.
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Old 30-06-2020, 22:58   #3
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Re: Suddenly Strong, Many GPS Signals

Quote:
Originally Posted by jstevens View Post
For some reason my little puck GPS receiver is reporting 15-18 satellites in use for a fix with SNR values above 40db. This from the GSV and GSA sentences received from the receiver. i noticed this a few days ago. Previously I was lucky to have 5 satellites in use for the fix with SNR values around 15DB. Nothing, I am aware of, has changed in the interim.
Here is a screen capture of software I wrote which displays the satellites. 10 GPS satellites and 8 Glonass satellites. Never saw this in the past. Anyone else having the same experience or have an explanation.
https://www.screencast.com/t/jZAmR2E8riy

My Samsung phone currently 27/28:

Circle: GPS
Triangle Glonass
Star: Beidou

Square: QZSS


(Display from GPS Test Plus)
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Old 01-07-2020, 07:13   #4
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Re: Suddenly Strong, Many GPS Signals

StuM, your phone seems to be getting an even greater number of satellites in use in SE Asia than my gps puck in Florida with similar high SNR values (>40 db). Is this normal in your area.

I'm still getting 15-18 satellites. My GPS receiver on this PC uses the SiRF chipset, not sure what version.

I guess this must some atmospheric change.

John
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Old 01-07-2020, 07:26   #5
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Re: Suddenly Strong, Many GPS Signals

Just realized what may caused the change in GPS reception for me. I changed computers
a couple of weeks ago and plugged the GPS into a USB-C hub. Maybe the GPS is just getting more power. I don't remember if I checked the satellite coverage until very recently. So maybe just a equipment upgrade on my part.

John
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Old 01-07-2020, 09:12   #6
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Re: Suddenly Strong, Many GPS Signals

The solar flux level is quite low at the moment... dropped last week. No sun spots. Good for GPS, bad for radio transmission.
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Old 01-07-2020, 10:36   #7
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Re: Suddenly Strong, Many GPS Signals

SpaceX launched a new GPS satellite on Friday for the military but it seems too soon for it to be in service. Most news reports that I've seen have focused on landing the booster so that it can be reused.
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Old 01-07-2020, 10:48   #8
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Re: Suddenly Strong, Many GPS Signals

June 22
Hong Kong (CNN Business)China launched the last satellite in its Beidou navigation network on Tuesday, completing a new rival to GPS and cementing its place in an elite group of countries with their own global navigation satellite systems (GNSS).

To date, there are only four major GNSS networks: GPS (US), GLONASS (Russia), Galileo (European Union) and now Beidou. India and Japan operate smaller systems.
Most people are familiar with GPS, which is used for everything from personal navigation on your smartphone to tracking planes and container ships around the world.
Beidou is China's alternative system. It's named after the Chinese word for the Big Dipper constellation, and has taken almost two decades to complete.
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Old 01-07-2020, 11:35   #9
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Re: Suddenly Strong, Many GPS Signals

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Originally Posted by Lepke View Post
Depends on where you're at. Russian satellites aren't world wide yet, mostly in the northern latitudes.
Interesting comment. I am not sure how the Russians would keep their satellites in the northern latitudes. Are the orbits of the Russian satellites inclined like the GPS orbits are? Are the orbits and placement of the satellites in the orbits such that they only have enough satellites available at certain times of the day?

Just asking.

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Old 01-07-2020, 11:53   #10
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Re: Suddenly Strong, Many GPS Signals

I assume the Russians built their system to mostly serve Russian areas until they have more money to spend. Operating in Alaska, I see more Glonass there than down south. No idea where or how their satellites orbit. Not my department.
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Old 01-07-2020, 17:26   #11
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Re: Suddenly Strong, Many GPS Signals

Quote:
Originally Posted by jstevens View Post
StuM, your phone seems to be getting an even greater number of satellites in use in SE Asia than my gps puck in Florida with similar high SNR values (>40 db). Is this normal in your area.

I'm still getting 15-18 satellites. My GPS receiver on this PC uses the SiRF chipset, not sure what version.

I guess this must some atmospheric change.

John

Yep, 4 x QZSS(Japanese), 35 x Beidou (Chinese) and 24 x GLONASS satellites make all the difference.


You may or may not be able to pick up some of them in the US. It's all tied up with this: https://www.gps.gov/spectrum/foreign/

and the design of the chips and software in GPS equipment sold in the US
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Old 01-07-2020, 19:04   #12
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Re: Suddenly Strong, Many GPS Signals

Quote:
Originally Posted by jstevens View Post
Just realized what may caused the change in GPS reception for me. I changed computers
a couple of weeks ago and plugged the GPS into a USB-C hub. Maybe the GPS is just getting more power. I don't remember if I checked the satellite coverage until very recently. So maybe just a equipment upgrade on my part.

John
GPS signals are very small signals.
It might be that the change to USB-C Hub is offering power with less interference and so your receiver can hear lower signals.

Basically the previous power source has RF noise getting into the GPS or the proximity to a computer that is generating noise.
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Old 02-07-2020, 11:11   #13
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Re: Suddenly Strong, Many GPS Signals

I went to an evening lecture last year on GPS signals. The professor works on improving reception and signal spoofing rejection. How GPS works at such low signal levels is pretty impressive.

A couple of example problems that he gives left an impression. One is drone in-air refueling. The drone is underneath the tanker, which shields the sky. They are both relying on GPS, not some vision system to fly the fueling pattern.

Another is the autonomous car driving down a street at the base of skyscrapers. No way you will have multisatellite reception in that canyon.

And then there is the ability of the enemy to spoof GPS signals in order to steal a drone.... its been done.

He also mentioned some projects where semi's carrying GPS blockers have disrupted aircraft landing systems as they pass by the airports.

These are very weak signals. That they are usable at all is pretty amazing. Yet through the magic occurring in these labs, they are getting better all the time.

I'd love to know if the USB C adapter made the difference. I'll change tomorrow.
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Old 02-07-2020, 11:20   #14
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Re: Suddenly Strong, Many GPS Signals

I don't think the difference is the USB-C port. I connected the GPS to a standard USB port and still got 18 satellites. I think the difference was getting off an old laptop with failing USB ports. I'm too lazy to go back to the old PC and see if it still receives only 5 or 6 sats. I'm just happy to have a solid fix.

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Old 02-07-2020, 17:37   #15
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Re: Suddenly Strong, Many GPS Signals

Quote:
Originally Posted by jstevens View Post
I don't think the difference is the USB-C port. I connected the GPS to a standard USB port and still got 18 satellites. I think the difference was getting off an old laptop with failing USB ports. I'm too lazy to go back to the old PC and see if it still receives only 5 or 6 sats. I'm just happy to have a solid fix.

john

I really can't see how the USB port can have an effect. The communication is done after all the GPS radio signals have been processed.
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