It's Elementary! Posted October 5, 2003 Share Posted October 5, 2003 Okay, I hope this is in the right place. If it isn't I apolizize to any Mods/Admins. Anyways, on to my question. We (the It's Elementary! team) are fairly new to this wonderful sport you people call Gecaching. We think we have the basic idea and have already found four caches. But this is no thanks whatsoever to our GPS, we have a Magellan SporTrak Map practically brand new. And it get's us close to the cache, but it never says we're right next to it, the distance bounces around unprectibly, we know that the direction arrow, is supoosed to be a little inacurate in tree-cover, but we are unaware of the distance doing so. Furthermore, whenever we are right next to the cache, the GPS usually settles on a distance between 28 and 41 feet away. Any help in solving this problem will be greatly appreciated. Quote Link to comment
+nincehelser Posted October 5, 2003 Share Posted October 5, 2003 It doesn't sound like there is a problem. That's typical GPS behavior, and your error isn't unusual. George Quote Link to comment
+PDOP's Posted October 5, 2003 Share Posted October 5, 2003 quote:Furthermore, whenever we are right next to the cache, the GPS usually settles on a distance between 28 and 41 feet away. These distances are typical of the accuracy of a recreational GPSr of 10 to 15 metres. The GPSr will get you close but you can't expect it to be right on. Centimetre level accuracy survey units cost $10K plus. PDOP's GPS Pages Quote Link to comment
+TerraTrekkers Posted October 5, 2003 Share Posted October 5, 2003 Add to that the same amount of error to the person hiding the cache and you have effectively doubled that distance. What would be the fun it it took you rught to it? TerraTrekkers =[]= Jim & Deb Quote Link to comment
It's Elementary! Posted October 5, 2003 Author Share Posted October 5, 2003 Well, yes but we have a 3 meter accuracy.... You'd think we'd be at least a bit closer... Quote Link to comment
+JamesJM Posted October 5, 2003 Share Posted October 5, 2003 Sort of on the theme of your other replies...."sort of". <smile> When I placed my first cache I was SOOOO deligent in getting PERFECT coordinates...as if "perfect" was achievable. Now....pfffft. REally! Yes, I do as well as I can but "in the area" is MORE than good enough. In 'geocaching' terms I am a novice with barely 100 finds....yet in all of those only ONE did my GPS show "dead on" positioning. I have found a few nearing 60 feet in distance from where my GPS said it was. I'm sure others will take this opportunity to say, "60 FT? I walked through 2' feet of sn....I mean.....I was 3,497 feet away". That's the fun, when you think of it. "Finding" is the key. - JamesJM Quote Link to comment
+PDOP's Posted October 5, 2003 Share Posted October 5, 2003 quote:Originally posted by It's Elementary!:Well, yes but we have a 3 meter accuracy.... That figure was calculated by the same people that base monitor size on diagonal measurements - it don't mean much but it sounds good. PDOP's GPS Pages Quote Link to comment
Bobthearch Posted October 5, 2003 Share Posted October 5, 2003 The behavior you're noticed is just the nature of GPS. What I do is get a good signal with a steady direction and distance, and then pace off to the location. If you do this from two or three different directions into the area of the cache, it's referred to as 'triangulating' and will get you very close most times. I've been around those backpack Trimple units that are absolutely dead on. Not only do these units cost way over $10,000, they are effective because they measure locations from known-position ground stations, not from orbiting satellites. Best Wishes, Bob Quote Link to comment
+PDOP's Posted October 5, 2003 Share Posted October 5, 2003 quote:Originally posted by Bobthearch:I've been around those backpack Trimple units that are absolutely dead on. Not only do these units cost way over $10,000, they are effective because they measure locations from known-position ground stations, not from orbiting satellites. Bob Actually they measure the errors ocurring at the known position stations and use that to correct the satellite signal errors for the roving GPSr. They do still use the signals from the orbiting GPS satellites. PDOP's GPS Pages Quote Link to comment
Bobthearch Posted October 5, 2003 Share Posted October 5, 2003 hmmm... even more complicated than I thought. I guess I knew they couldn't get a location with just one ground station; they would need multiple stations to triangulate. Never used one myself, but been around them plenty. Best Wishes, bob Quote Link to comment
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