GPS Accuracy

[brady]

I recently purchased a GPS12. Have been testing it
out when out walking and it does not seem to be accurate consistently within as much as a 100feet.What is the experience out there.

[bob oh]

GPS is usually advertised to be accurate to within 100 yards, 95 % of the time. So unless you got a defective unit, which is unlikely, it should be about as acccurate as any other GPS, unless the another GPS is corrected with DGPS. Usually accuracy is much better, but there is an error at times introduced by the US Gov't. for security pruposes (their claim not mine). But, GPS is not a dead-on accurate navigational tool so you should keep that in mind when you are using it.

[Doug/CO]

I also have the Garmin GPS12. It's one of the least expensive units available, but very useful when pinpoint accuracy is not necessary. I've used mine to help find camp after chasing elk for several miles in the mountains. Accuracy seems to vary from about 200 feet to dead on. It will definitely help you to find your camp or your truck in the wilderness, but is not so precise as to find a small drop-off or small hump in the middle of open water. It will find larger sunken islands, and certainly put you in close proximity to whatever point you have marked. Overall, I'm very happy with mine. The AC adapter is a nice addition for use in your truck or boat. You may have noticed that these things use lots of batteries. Keep your powder dry.

[brady]

thanks for your reply. I was hoping the GPS was precise enough to find the fishing spots. But after using it some I agree it will get you close but you will need to use the depth finder from there and judge from the lake map contours.

[Mark1]

Have used GPS for a few years however, not familiar with DGPS. Please define what DGPS is and where I can obtain literature on DGPS.

[Tony]

DGPS is "D" for defense or the military.That is the pinpoint accuracy system they used to drop bombs down the chimmneys in Desert Storm.The general puplic does not have access to that technology at this time.You can buy a GPS that is "DGPS" ready when they decide to release the technology.
Don't know where to get more technical data.

[hagar]

you can buy a DGPS antenna for your GPS now. The limiting factor is there needs to be coverage for the area you plan to use it for. These are mostly(if not all) Coast Guard stations. If you go to the Coast Guard web site I believe there is a page for DGPS coverage. Also from what I understand and someone correct me if I am wrong in the not to distant future they are going to be removing the random errors that are programmed in.

[Denied]

LAST EDITED ON Apr-07-00 AT 10:32AM (CST)[p]Many GPS units are DGPS capable. (The "D" stands for Differential, which is a built in "inaccuracy") With an additional antenna, you will recieve a correction factor which make your unit more accurate. I have a Lowrance LMS 350A, which is DGPS capable. I added the DGPS antenna (beacon receiver) which helped greatly. A normal GPS is accurate to within 100 meters. With the addition of the DGPS beacon receiver I get 10 meter accuracy... Hope this helps clarify.
Check to see if DGPS stations are available in your area before buying one.On Erie we get the Detroit station.

Fishing Western Lake Erie aboard "DENIED"
http://my.ohio.voyager.net/~cliftond

[muskyhigh]

DGPS uses a ground station with a know latitude and longitude to correct for the programmed error in "CE" code gps satelite transmission. CE is for civilian use only and it has error randomly thrown into it. "PE" code GPS is the reciever that the military uses. It removes that error however it is still mostly accurate to about 10 meters. They still use DGPS when really accurate measurements are required.

[Bret N]

I have the Garmin 12 and find that it is an accurate unit. When you save a waypoint make sure that you use the position averaging feature. This makes it much more accurate. The unit will actually calculate the built in error of the signal usually to + or - 20-30 feet. This helps quite a bit. Still I have been off from a known spot as much as 40 yards, depends on how much the military is degrading the signal at any given time and date. Hope this helps. Bret

[Phil T.]

http://www.navcen.uscg.mil/dgps/coverage

[bob oh]

LAST EDITED ON Apr-07-00 AT 11:29AM (CST)[p]You can buy DGPS antennas from many manufacturers. But as stated, you need to make sure there is coverage for your area because DGPS is ground based. It helps correct GPS and can be dead-on to about 5 meters (I believe) off. The government is talking about removing the error that is introduced in GPS, but I don't know of a firm date and in any case, GPS without error still will not be as accurate as GPS with DGPS....If you want some great info on GPS check out the newsgroup sci.geo.satellite-nav - a lot of experts there who are usually very helpful
Bob

[hagar]

This is the page for the Coast Guard
www.navcen.uscg.mil/dgps/coverage/default.htm

[Mark]

True, the Garmin 12 in no less accurate than the Lowrance or the Magellan. They all recieve the same signals and triangulate, which is really quite simple math for a computer to do.

[Mark]

True, the Garmin 12 in no less accurate than the Lowrance or the Magellan. They all recieve the same signals and triangulate, which is really quite simple math for a computer to do.