warning be careful with gps right now

[grunk36]

you have to be very careful with checking your gps on your fixpoints several times a day right now
there is some solar eruptions and solar storms that do disturb the gps signal and f.... everything up i had a incident the other day where i suddenly did not get near the finished surface we had just done and when we checked the coordinates i was 2,5 meters off in the northing plane and 30 cm in design elevation BUT the elevation was still spot on so this is very spooky

 

[watglen]

i was warned that ag gps may have issues this spring as well. Same story, solar activity messing up the signals.

 

[watglen]

I suspect ( i'm no expert) that the sun activity will cause corruption of the signal data on its way from the satellite to the GPS antenna. The GPS receiver will discard the data as corrupt, and the number of satellites will drop. The end result is a reduction of the number of satellites the receiver shows as "tracking".

Last year you may have had 8 satellites, this year, because of the solar activity, you may only have 5 or 6. For some systems, that isn't enough to resolve a position.

The most important thing is the system is smart enough to know how accurate it's computed positions are, and will warn if it is not getting enough satellite data to do a good job.

 

[lgammon]

oh my we might just have to start grading my stakes and skill now, what ever will we do!!!!!..j/k just a little guy that really wants gps.

 

[watglen]

There is a push this year to do what is called a "Glonass Upgrade". Depending on your equipment, you need either software or hardware to include the Russian gps sat feeds for the position calcs. Adding another 6 or 8 russian birds will give lots of data and ensure accuracy. Also, since the Glonass system is newer, I'm told it has features they never thought of for the North American system.

Wikipedia also says the Chinese and Indians have, or are working on systems of their own. And, of course there is the European system "Galileo" system.

 

[LWG]

You can call the Flight Service Station system, 1 800 WX BRIEF and ask for the status of GPS satellites. They will tell you whether satellites are out, and which ones. They will also be able to tell you about system outages.

A bigger threat is the broadband system called Light Squared. Older GPS systems are not filtered for the frequencies this new system uses, and the new system could cause significant interference with older GPS systems.

 

[vapor300]

The glonass satelites are the worst, i never use them i always shut them off, i dont know how many times ive done something using the glonass satelites only to come back the next day and it be 3-5 tenths off

 

[alaskaforby4]

What are the situations where GPS can malfunction? We have a situation where we are loading out trucks at pit, when they get to the site they are saying it is 25% short. I have created a perfect square box and measured the yardage. it is spot on, I can see a few percent plus or minus, but 25? I went to the site and they showed me the topcon set up, they shot a base elevation and then random spots around base, middle and top of pile for 1 end dump pile and the calculations are showing 25% less. I have limited knowledge of GPS, what could be going on?

 

[CM1995]

Alaska are they taking into account a shrink/swell factor? 25% is the number I use to swell bank yards in a truck.

In other words if I need 100 CY of compacted fill imported onto a job site from a pit, I will need to move 125 loose CY's from the pit in order to get 100 CY of compacted fill on the project site.

Say you're getting 20 CY per truck you, will need 6 loads and a 5CY finish up from the pit to get 100 compacted CY on the job site.

 

[Nige]

As above. Swell factor means that for every yard of "bank" (in situ) measurement you can have anything from 25-33% of swell factor to what the loose material volume will be.
Try and get hold of a Cat Performance Handbook. It contains some interesting info on calculating earthmoving data. Below is a quick snip from the Earthmoving section.
You can download a copy of the latest version here. Be warned though, it's 72MB in size - https://wheelercat.com/company/resources/cat-performance-handbook/

 

[alaskaforby4]

Thanks guys, unfortunately it isnt a compaction or swell issue, rather loose yards, dumped in individual piles. We say we're loading one thing by our tests, they say they are getting 25% less. Age old contractor and supplier discrepancies playing out in real time! Looking for the middle ground, I would think filling a perfect square area would prove any questions, but they are trusting the GPS more than math...The world we live in

 

[John C.]

Who is doing the measurements? Is the payment for service based on the amount of material moved?

 

[doublewide]

Sounds to me like they're trying to beat you.

 

[Trashman]

Always measure what you move in bank yards, not by the capacity of the truck. You're just setting yourself up for disappointment, if you do. LOL

 

[nerdstick_joe]

What are the situations where GPS can malfunction? We have a situation where we are loading out trucks at pit, when they get to the site they are saying it is 25% short. I have created a perfect square box and measured the yardage. it is spot on, I can see a few percent plus or minus, but 25? I went to the site and they showed me the topcon set up, they shot a base elevation and then random spots around base, middle and top of pile for 1 end dump pile and the calculations are showing 25% less. I have limited knowledge of GPS, what could be going on?

I would question their measuring techniques. There's a way to do volume calculations that involves creating a base surface, and comparing that to the pile surface. This method is usually pretty spot on. To put it simply: they would need to do a topo of the base of the pile; then create a surface. After that to a topo of the whole pile, create a surface from that. Then compare it. If their measuring technique is proper, I'd look at version of software they're running, or checking that their elevations are matching up against whatever they're using. Just a couple of options. Would need to know more about the situation.