GPS Questions

Mopar Bob said:
Conclusion #1: Clouds do affect GPS reception. At least Phantom reception. Not all clouds however. Those puffy white things don't seem to have any effect on the reception. However, dark clouds that cover the entire sky dome do affect it. I went to the same field for a few days. Overcast one day, 6-8 sats. Clear skies, 10-12 sats. I repeated this test twice with the same conclusion. Within the course of an afternoon, the heavily overcast skies cleared up, and my reception did also.

The frequency of the signals sent from the GPS satellites was chosen so that they wouldn't be affected by cloud cover and rain. GPS navigation is an all-weather system for planes, boats and cars. They don't all have to switch to an alternative when it rains. The number of sats visible at any location varies with time and it looks like your testing doesn't account for that.
 
Mopar Bob said:
Conclusion #4: The foil mod does require the use of aluminum and not copper. I had done mine with copper sheets that are used to insulate humming in a guitar amp. I saw no change in my reception. I pulled it out and used aluminum. Big difference. Although copper is a better conductor of electricity, apparently, aluminum is a better insulator of EMI (electro magnetic interference).

Interesting as tests by other members show that copper improves their sat count pretty dramatically. Also interesting that in other applications where EMI shielding is essential copper is also used. This seems to be a matter of preference than any actual hard data as far as I can tell.

Thanks for sharing your findings. The more we share the better off we all are!
 
job2310: 3M did a study of EMI shielding effectiveness. Copper was rated at about 85% and aluminum at 92%. But tin plated copper that was embossed is rated at 96% effective. I am not sure where to buy the stuff but the 3M number is 1345.

Meta4: I agree with you in principle and I do appreciate your opinion. But something is affecting the reception. For instance, I have the Phantom hovering in a spot for 10 minutes. As the weather front moves overhead, I am watching the satellite count change from 10 to 8 then back to 10 then 7 all in a matter of minutes. As I stated in my original post, "is there a possibility there is something wrong with my GPS unit". If no one else has this problem, and sat designs are such that atmospheric conditions have no bearing on the sat reception, then the conclusion must be its my unit. OR, it's just a shitty design using minimally tolerant parts so you have a large fluctuation in how well or poorly these things operate. My guess it is the latter. These birds are very well constructed. The solder joints are perfect, the fit and finish is excellent. But Chinese production has a reputation for borderline components. I thinks that is the case here.
 
There are definite effects from atmospheric conditions and the satellites are moving... there will be a [normal] fluctuation in 'count' from time to time as a result.
 
Yes the orbits of the satellites means that they are coming and going frequently.
Check the GPS app to see how the sats it can see are behaving too instead of just what the Phantom shows.
Is there a significant difference?
 
Mopar Bob said:
job2310: 3M did a study of EMI shielding effectiveness. Copper was rated at about 85% and aluminum at 92%. But tin plated copper that was embossed is rated at 96% effective. I am not sure where to buy the stuff but the 3M number is 1345.

Meta4: I agree with you in principle and I do appreciate your opinion. But something is affecting the reception. For instance, I have the Phantom hovering in a spot for 10 minutes. As the weather front moves overhead, I am watching the satellite count change from 10 to 8 then back to 10 then 7 all in a matter of minutes. As I stated in my original post, "is there a possibility there is something wrong with my GPS unit". If no one else has this problem, and sat designs are such that atmospheric conditions have no bearing on the sat reception, then the conclusion must be its my unit. OR, it's just a shitty design using minimally tolerant parts so you have a large fluctuation in how well or poorly these things operate. My guess it is the latter. These birds are very well constructed. The solder joints are perfect, the fit and finish is excellent. But Chinese production has a reputation for borderline components. I thinks that is the case here.

Here it is and it ain't cheap!

http://www.amazon.com/3M-1345-SHIELD-CO ... B005T8INGQ
 
Meta4 said:
The frequency of the signals sent from the GPS satellites was chosen so that they wouldn't be affected by cloud cover and rain. GPS navigation is an all-weather system for planes, boats and cars.

That is false, signal strength of the 1.5Ghz L1 GPS signal is affected by weather and cloud cover like all other Radio frequencies are and it also has an effect on accuracy because signal timing is critical for accurate positioning. Military GPS systems use 2 different frequencies at the same time to calculate the deviations caused by atmospheric and ionospheric conditions thus improve the accuracy.
 
No .. this is a common myth. The effects of cloud are not enough to be noticed.
If GPS was affected by weather enough to affect practical accuracy the system would be worthless.
The whole point of GPS is to provide location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. If it only worked in fine weather the system would be worthless.
Here are a few references.

Garmin website .. GPS works in any weather conditions
That site goes on to list 7 sources of GPS signal error - none of them are weather related.

or The US Coast Guard Navigaton Centre http://www.navcen.uscg.gov/?pageName=gpsFaq
GPS is a satellite-based radionavigation system developed and operated by the U.S. Department of Defense (DOD). GPS permits land, sea, and airborne users to determine their three-dimensional position, velocity, and time 24 hours a day, in all weather, anywhere in the world with a precision and accuracy far better than other radionavigation systems available today or in the foreseeable future.

NOAA http://www.esrl.noaa.gov/gsd/publicatio ... f300b.html
The ability to use the Global Positioning System (GPS) to make accurate refractivity measurements under all weather conditions .....

Dr. R. A. Anthes et al., 2008, in The COSMIC/FORMOSAT-3 Mission: Early Results published in the Bulletin of the American Meteorological Society (Volume 89, Issue 3):

"The radio occultation (RO) technique, which makes use of radio signals transmitted by the global positioning system (GPS) satellites, has emerged as a powerful and relatively inexpensive approach for sounding the global atmosphere with high precision, accuracy, and vertical resolution in all weather and over both land and ocean.

or http://www.gpsinformation.net/gpsclouds.htm
 
:) I think you should re-read the NOAA article, they are using the GPS signal to detect water vapor since it causes a delay in the signal
Btw I never said that it won't work in bad weather conditions, I said that it has an effect on signal strength and signal travel time!
 

Members online

No members online now.

Forum statistics

Threads
143,066
Messages
1,467,358
Members
104,936
Latest member
hirehackers