GPS & Power Line Interference: Is it real?

Lee Hixson · Post by **Lee Hixson** » Mon Oct 05, 2009 6:45 am

Being curious about any controlled studies about the effects of high voltage power lines on GPS signals, I did a Google search and only came up with one article of relevance:

GPS interference – According to a study by the Institute of Electronics and Electrical Engineers (IEEE), power line conductors are unlikely to cause signal degradation to GPS signals. The study noted no loss of satellite signals as the GPS receiver moved across a power line easement. A GPS receiver relies on a dispersed constellation of satellites – at least four and often more.
Use of Global Positioning System (GPS) Receivers Under Power-Line Conductors, IEEE Transactions On Power Delivery, Vol. 17, No. 4, October 2002.

This makes me wonder: is it just a theoretical possibility, or do we have hard evidence that we need to worry about signal interference under/near a power line? And if the answer is "yes," to what degree is the signal degraded, and how far away from the power line is it a problem?

Anecdotal evidence is welcomed, but I'd prefer hard evidence in the form of controlled, scientific studies.

Thanks, Lee

Gromatici · Post by **Gromatici** » Mon Oct 05, 2009 7:13 am

I don't think that you're going to loose the signal (and it's not what were concerned about as surveyors anyway) so that study does not mean much to surveyors. What is going to happen in radio interference or "noise" that may degrade you radio link enough to cause measurement errors and possibly cause multi-path with the satellites.

I haven't done any controlled experiments but have been told this by the sales reps and GPS consultants.

From experience I know not to use the GPS next to tall fences (maybe something to do with the antenna?) tall buildings and up next to a power pole due to it messing with my math.

Personally, you'll see the vertical degrade before the horizontal.

Stan_K · Post by **Stan_K** » Mon Oct 05, 2009 9:01 am

Lee: My personal experience says yes. The interference caused by the electrical current and voltage has an effect similar to multipath. It usually effects only one or two birds. I have documented positional errors to 0.1 to 1.5 meters. The antenna and internal algorithms determine the effect and consequences. Just another error source to identify and eliminate.

Stan

Paul Goebel · Post by **Paul Goebel** » Tue Oct 06, 2009 9:08 am

I have experienced multipath problems around steel high tension tower structures, but not in the areas between them and under the lines themselves.

Lee Hixson · Post by **Lee Hixson** » Wed Oct 07, 2009 5:08 am

As a follow-up, yesterday I got feedback from PG&E that they routinely get good readings near, even directly under, power lines...that the only time they get bad readings is when they try to shoot the center of a large steel structure. It's their opinion that it's the structure itself, not the lines, that they need to watch out for.

Scott Tikalsky · Post by **Scott Tikalsky** » Wed Oct 14, 2009 12:03 pm

Lee;

Our company did a subdivision in Johnson Park (near Burney) a couple of years ago. There is a large electric transmission line running along the north side of the project. While I was trying to tie property corners and Caltrans monuments located north of this corridor, I had to walk through the easement. When I was still a couple of hundred feet from the lines, I had good satellite coverage (6 or more satellites). As I walked toward the easement, the satellites started to wink out. I tried this a couple of times to make sure what I was seeing was actually happening. This made a believer out of me.

goodgps · Post by **goodgps** » Fri Oct 16, 2009 4:53 am

Those High power transmission lines do interfere with GPS and also, can really send a jolt thru your total station or theodolite. Anyone else ever get "eyelid burn" from using an instrument too close to those lines ?

Another thing those lines do is interfere with your RTK link. i've also noticed that "ham" radio interferes too.

Nothing is for free is it ?

"good"

Paul Goebel · Post by **Paul Goebel** » Fri Oct 16, 2009 4:54 pm

Good, I'm interested in hearing more about "eyelid burn".

I don't have any empirical evidence, but is seems plausible to me that those high power lines might affect any electronic device, even if it complies with FCC rules. If I had a really important point to shoot under there, I probably would be cautious about using GPS.

goodgps · Post by **goodgps** » Tue Nov 03, 2009 9:14 pm

The static from overhead lines, actually was "snapping" thru the T16 right onto my eyelid.
We were in such a hurry, I kept turning angles from that spot until we moved.
I kept looking for that "burr" on the eyepiece, thinking that perhaps the gun had been dropped by another crew. We soon relized the source when the Philly rod, welded together and we had to un weld it to put it away.

Took about a week for the blister to go away.

As far as GPS, something we did yesterday, when confronted by power lines, was to hold a brass shield like photographers do with their shadings.

It WORKED !!! we got a great shot, and missed record distance and angle, by a couple of hundreths. (RTK) we always inverse and check azimuths to see if anything went wrong.

Guard your brass, from tweekers who want to recycle it.
I found mine in a field near an industrial park.

600d

PLS7393 · Post by **PLS7393** » Wed Nov 04, 2009 8:59 am

I do not have direct data relative to GPS and high voltage lines, but on a similar note as Good mentioned, total stations have burped and given wrong distances when shooting around or across high voltage lines.

If we all think long enough, I have to think we are not the only ones with this issue with total stations working around high voltage lines. With this proof, how can the GPS data not be effected?

Thats my 0.02

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