GPS Accuracy

F9K9 · Post by **F9K9** » Sat Jul 08, 2006 10:03 am

HenryJ wrote:
killian96ss wrote:
2kwik4u wrote:I'll run GPS on it this weekend and see what I come up with, but 23mpg on the highway doesn't sound out of place to me.

I mentioned this problem over at ZR2.com once, so I'll mention it here also. GPS is not accurate for speed calibrations.
Accuracy of the original GPS system, which was subject to accuracy degradation under the government-imposed Selective Availability (SA) program was an issue with speed and position. The military released their hold on the WAAS technology quite some time ago. While not all GPS receivers have the same accuracy, many are extremely accurate. The VBOX is an example of some of the newer applications using the GPS technology.

I have to agree with HenryJ on this one. However, I do not believe that the military stopped the SA program intentionally. If, you remember the big panic preceding midnight December 31, 1999, the GPS satellite shutdown was a major concern.

Having used military and civilian GPS receivers for several years prior to that date and dealing with the civilian units inherent inaccuracy, I just find the military's timing to release the technology at that exact date and time to be to big of a coincidence. The President announced in May of 2000 that the SA program would be stopped immediately. That improved the average civilian unit 10 fold. We had already noticed much earlier than May that there was virtually no difference between military and civilian GPS receivers.

Post by **HenryJ** » Sat Jul 08, 2006 10:19 am

Here is a good site for independent testing on numerous models- GPS Information.net

GPSinformation.net WAAS , Garmin WAAS information , Wikipedia WAAS , Stanford GPS lab , FAA WAAS

U.S. transportation, public safety, economic, scientific, timing, and other users rely on GPS extensively. In aviation and maritime transportation, GPS is used for "safety of life" navigation and it is a critical system for these applications. DOD is the steward of the system, responsible to maintain the signal specification; the PNT provides management oversight to assure that civil and military needs are properly balanced.

FAA FAQ

F9K9 · Post by **F9K9** » Sat Jul 08, 2006 10:48 am

On May 1, 2000 the President announced that effective immediately, the use of SA would be discontinued. This will result in accuracies up to ten times more accurate than previously possible. All users worldwide will benefit from these commitments.

F9K9 · Post by **F9K9** » Sat Jul 08, 2006 4:28 pm

One additional note from the controversy on the Stock Crew Cab thread is that civilian (non avionics) GPS receivers are a little wacky at the elevation readings.

I have looked for the thread on the Delorme forum but, am unable to find it now. I have been a software beta tester for Delorme for over two years. Delorme GPS software provides a way to playback a route that you traveled. One member captured a screen shot while descending into Death Valley giving an elevation of something wild like -12,000 feet below sea level.

Outside of the elevation glitch I can see no difference between civilian and military GPS receivers and that is working with them from '91 to '02. The big change was made in '00

chumley · Post by **chumley** » Sun Jul 09, 2006 2:22 am

Do you have any experience/ knowledge with Trimble? The company I work for has it on most of our heavy equiptment and all the excavation foreman (what I do) have a "rover" which is a portable unit that we do surveying with. It is truly awesome stuff when you can grade roads and retention basins and everything on a jobsite to a tenth of an inch with no stakeout in a dozer!

F9K9 · Post by **F9K9** » Sun Jul 09, 2006 3:05 am

chumley wrote:Do you have any experience/ knowledge with Trimble? The company I work for has it on most of our heavy equiptment and all the excavation foreman (what I do) have a "rover" which is a portable unit that we do surveying with. It is truly awesome stuff when you can grade roads and retention basins and everything on a jobsite to a tenth of an inch with no stakeout in a dozer!

I remember that now from an Thread here. I also forgot that they're used in surveying. Remember the miners trapped in PA a couple yrs ago? The location to drill the hole that finally got then out was determined by a surveyor. A couple feet in any direction and that hole could of been in a mine pillar causing the rescue team not find the air space. He used GPS for that brilliant piece of work.

Post by **HenryJ** » Sun Jul 09, 2006 5:51 am

chumley wrote:Do you have any experience/ knowledge with Trimble?

No. I migrated away from running the heavy equipment before GPS was introduced. I know that ariel applicators are using it for coverage and ground speed while applying chemicals.
I have a friend that is doing some detailed utility GIS mapping.

Here is a source for some of the "industrial" GIS units - Thales Navagation