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You ever find out how much more accurate gps position is with 19 satellites vs 12 satellites? We chatted about this some time ago and you said you would get the answer and get back with me. I ain't forgot. I do have good recall on things of interest.:)
No I have not CP. In a phone conversation I was told that it would depend on where the 12 versus 19 satellites were plus their signal strength and so on… stuff we already knew. I was looking for a generalized difference of like 0.98 meters or something like that. I don’t know that I can pry that out of them.
If you need help pulling teeth, let me know. I just got a new hook remover. I believe you number .98 meters to be bit high, but I don't know and can't prove it.
The .98 meters was just a number I pulled out of the air CP; it was not based on anyting but was used to show that I was looking for a distance to quote and not that it mattered on this, and this, and this...
I understand. I just pulled .01 meters out of the air. Must be because I am in Tennessee. ha
ON survey grade GPS equip, they're talking 3 centermeters of accuracy. Meaning that if I survey a point, I'll be within 3 centermeters of exactly where it's at. They're also being more work on the Ellipsoid of the Earth to adjust things out even better. Before to get that accurate, I'd have to set my GPS up and let it run for about 20-30 minutes, now I can do that in just a couple minutes
I thought the survey grade used 2 frequencies??
Doesn't the survey grade also use the ground stations for accuracy?
I believe your unit is the ground station.Quote:
Originally Posted by mduncan62
LOL. Talking about these below.Quote:
Originally Posted by Crappie Reaper
Ground Stations
The GPS control segment consists of several ground stations located around the world.
A master control station at Schriever Air Force Base in Colorado
Six unstaffed monitoring stations: Hawaii and Kwajalein in the Pacific Ocean; Diego Garcia in the Indian Ocean; Ascension Island in the Atlantic Ocean; Cape Canaveral, Florida and Colorado Springs, Colorado
Four large ground-antenna stations that send commands and data up to the satellites and collect telemetry back from them
Shows you how much I know...DOH! DohQuote:
Originally Posted by mduncan62
They're using one on the Miss Gulf coast as well from what they told us in the last Seminar. Yeh, it is Duel Freq. I do know that these Solar Flares lately have been giving us fits with accuracy. They're supposed to last I think for another year or so before all this solar activity slows down. Kinda scary when they told us about this extreme Solar activity cause I'd just rented and watched 2012 LOL
Survey grade GPS is almost always differential, meaning they place a station at an accurately surveyed point (real time) or use logged data from an error server such as some universities provide. At work, we use a server at IU for correction, which is about 25 miles away. Our stuff isn't surveying, but we need better accuracy than standard GPS. We put in our logged data, and the server goes back and looks at the error it was seeing at the times our readings were recorded and corrects our data.
Back to your original question CP, the shear number of satellites isn't the only important factor. The geometry is important too. Imagine two guys on a football field trying to triangulate a spot. If they are both standing on opposite ends of the 50 yard line and the spot is also on the 50, they will accurately place it on the line, but its exact location on that line is tough. If you place them right next to each other, again they willl have a hard time precisely locating the object. The best scenario puts both guys and the object on different corners of an equilateral triangle. The same situation exists for the satellites, only in 3 dimensions. They work best when they line from each satellite to the receiver is at about 90 degrees to the lines from the other satellites to the receiver. With good geometry, you can get accurate measurements with just a few satellites. More satellites can allow better error correction.
Here's a good link explaining sources of error GPS explained: Error sources