Mr_Scrub Posted November 15, 2002 Share Posted November 15, 2002 I just bought a new Sportrak Map for my first GPS unit. I notice that when I try to find a spot or backtrack the unit seems to keep on going for a bit when I stop. Is this normal? Is it "averaging"? If so, what is the benefit? Can I turn it off? Mr Scrub Columbia, SC. Quote Link to comment
+bradtal Posted November 15, 2002 Share Posted November 15, 2002 Mr. Scrub- You may notice a slight "delay" with your GPS as it is usually a second behind. You can see this when you are driving. Come to a complete stop and you will notice the speed finally drops to 0.0mph after a second or two. This is because the GPS is doing many calculations per second, but also needs "a few more data points" to do a calculation to determine if you are stopped. Disclaimer: You should not drive and look at your GPS at the same time, but it's kinda fun to do. Just be safe about it... Also, if you are at a standstill, you may notice your EPE switches to "Averaging". This means the gps is taking your location every second and averaging it out so it will be more accurate. For example, lets say over 5 seconds, my GPS came up with the following latitudes: 40.53356 40.53351 40.53351 40.53352 40.53351 It would average out to 40.53352. Notice the first one is kinda a "bogus" read, but the others are "closer" together and will make a more accurate reading. (even though all of those readings are pretty darn accurate! ) The Averaging is handy when hiding a cache or when you are trying to get an accurate location (like the corner of your property, or marking "dog piles" in your local park... Seriously! Check out Dog Pile Webpage) You can set your GPS down for a minute or so and you should get a very accurate reading (if tree cover, mountain ridges, etc don't hinder the satellite readings). Hope this helps. Brad Hard work pays off in the future, laziness pays off now. Quote Link to comment
+Olar Posted November 15, 2002 Share Posted November 15, 2002 quote:Originally posted by Mr_Scrub:I just bought a new Sportrak Map for my first GPS unit. I notice that when I try to find a spot or backtrack the unit seems to keep on going for a bit when I stop. Is this normal? Is it "averaging"? If so, what is the benefit? Can I turn it off? Mr Scrub Columbia, SC. Yes its normal particularly when you have marginal sat-lock like out in the woods. Like Bradtal mentioned the GPSR is a second behind anyway at the best of times. I think the condition has been referred to as "the sling-shot effect" in these forums. Thats why a lot of cachers will stop moving towards the cache approx. 100 ft. away in order to allow the unit to settle down and get a more accurate bearing and distance over the final 100 feet. Often I will stop around 50 metres and watch the distance drop 10 to 20 metres more. The averaging doesn't start untill you have come to a complete stop so it is not adding to the problem although in the early days with the Magellan 315, it would kick into auto averaging before you actually stopped moving and this caused a lot of grief. The averaging is very beneficial when hiding a cache and you want the most accurate coords to publish. Happy caching, Olar "Pi 'r not square, Pie 'r round you dummy!" Quote Link to comment
Mr_Scrub Posted November 15, 2002 Author Share Posted November 15, 2002 Thanks for the explanation. I hope to search for my first cache this weekend... Quote Link to comment
+sbell111 Posted November 15, 2002 Share Posted November 15, 2002 quote:Originally posted by bradtal:... The Averaging is handy when hiding a cache or when you are trying to get an accurate location (like the corner of your property, or marking "dog piles" in your local park... You can set your GPS down for a minute or so and you should get a very accurate reading ... Don't set it down on the dog pile, however. Whenever I feel blue, I start breathing again. Quote Link to comment
Kerry. Posted November 15, 2002 Share Posted November 15, 2002 Averaging, isn't all that it's cracked up to be and basically is comes down to a 50/50 chance of improving or actually making the position worse. The thing is one doesn't know at the time which 50% one is dealing with. http://www.cqnet.com.au/~user/aitken/gps/gps_avg.htm http://www.cqnet.com.au/~user/aitken/gps/gps_obs.htm http://www.cqnet.com.au/~user/aitken/gps/avg_pii.htm Averaging bad data simply gives a bad data average. Cheers, Kerry. I never get lost everybody keeps telling me where to go Quote Link to comment
+briansnat Posted November 16, 2002 Share Posted November 16, 2002 A waste. "You can't make a man by standing a sheep on its hind legs, but by standing a flock of sheep in that position, you can make a crowd of men" -Max Beerbohm Quote Link to comment
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