GPS question

[shaley]

I found this on a GPS site and I've been hearing it for 2 years now. Some of the marine GPS units say they have L2-c but I'm going to hold off for a year on a hand held. L2-C will be +- one foot accuracy. Current 3 place decimal is 6 ft b/c there is 6070 ft in a N mile.

"Recently, a new GPS satellite was put into orbit. This satellite is capable of broadcasting not only on the L1 (L1C) frequency, but also a new L2 frequency. (L2C actually, the C denoting civilian). Some people have indicated to me that consumer level GPS receivers will not start hitting the market until there are 24 functional satellites broadcasting L2C information."

 

[orezok]

And that is exactly what differential GPS does...

True, but the government still controls the differential signal which it can switch off at any time. Accuracy is improved to about a meter with differential. We set up our own base station and can improve accuracy to less than 1/8" and it can't shut down by others.

 

[RonMar]

True, but the government still controls the differential signal which it can switch off at any time. Accuracy is improved to about a meter with differential. We set up our own base station and can improve accuracy to less than 1/8" and it can't shut down by others.

Well concidering the government(DOD) still controls the GPS signal, and can shut it down for a whole global region whenever it feels the need, the USCG shutting off a diff beacon is not that big a deal. With Selective availability disabled now, I don't think too many are going to the trouble of installing or using DGPS beacon recievers anymore anyway. The base accuracy of the signal is plenty accurate without it.

What are you doing that needs 1/8" accuracy?

I escorted a USGS surveyor to one of our remote communications site so he could setup a receiver on a geodetic marker. They were comparing markers on both sides of the cascade range to see how much movement is being caused by the subduction zone in the pacific northwest. He had a specially machined $16K antenna coupled to a $3k receiver. No differential, just a high quality signal refined and averaged over a 20 hour period.

 

[orezok]

Survey for grading and improvements. All points need to be within +/- .001 foot (1/8") both horizontal and vertical. Vertical accuracy is almost imposible without an onsite base station.

 

[Tdog]

As a follow up, my gps problem apparantly has nothing to do with military bases being in the vicinity. Or at least the Garmin technician did not think so. He had me do a Master Reset & clear all my user preferences. Also he wanted to be sure I had the latest software, which I think I do. So far it has not screwed up, but I had used it OK for a couple of months before it messed up in the 1st place.
Whatever - - the Garmin techical help people were relatively easy to reach. Surprised me.

Jack

 

[archerynut]

I have my second 660 right now. One day for no apparent reason I got into my truck and the darn thing would not work. It was on but would not track satellites at all. Drove 25 miles and it never picked up a signal. Returned it to the store where I had bought it and have a brand new one that hasn't had any problems. Here's my thought, it was full force hot days (90+) here in PA and I think the thing just overheated something inside and it went dead, battery wouldn't charge either. Since then I never leave my GPS on the dash when the truck is parked. Always stow it in the center console.

 

[Tdog]

archnut, I never leave the unit on the dash. I try to take it down & stow it prior to stopping. Too easy a target on the dash for thieves.

When my failed last weekend, I was driving with the AC on - - & I had been traveling for several hours. It was not especially a hot day, maybe upper 80s. I don't think my problem was heat related. I'll be using it on local trips for while just to give it a chance to mess up. I suspect it won't do that till my next real road trip.