+phinstr Posted February 2, 2004 Share Posted February 2, 2004 (edited) I have an Etrex Yellow and it always seems to read ~30ft off. I know this is a less expensive model and I dont think it has WAAS but is this normal? I thought it would be closer...... All we do is Geocache so we do okay but my wife says "upgrade" ( ). Now, she is still a penny pincher so what is the next best bang for the buck? I probably need to stay under $200 or she'll have my... Though she has found more caches than I have. Do I need the maps? Do I need to connect to the computer? Maybe I should get a new one and give her the old! Phinstr Edited February 2, 2004 by Phinstr Quote Link to comment
+Lazyboy & Mitey Mite Posted February 2, 2004 Share Posted February 2, 2004 A buddy of mine, cheapest man on earth used his yellow etrex until it broke, then he bought another one. I use magellens. Many deals under 200 bucks with either brand, if you shop smart. You don't need maps and you don't NEED computer hookups but it's nice. Again, up to you. Quote Link to comment
+nincehelser Posted February 2, 2004 Share Posted February 2, 2004 (edited) It sounds normal. My son and I are currently comparing a yellow eTrex (no WAAS) readings with a Vista eTrex (WAAS enabled) for a school science project. We haven't crunched the data yet, but on the surface the numbers don't seem to be all that different. The only obvious thing that jumps out at me is that the WAAS unit seems much more confident in its measurements. I'll know more once we start graphing the data, but I'm suprised we're not seeing more of a difference between the two units. We're taking data over time from a single fixed point in an open area where the reception of the WAAS won't be a problem. George Edited February 2, 2004 by nincehelser Quote Link to comment
+GeckoGeek Posted February 2, 2004 Share Posted February 2, 2004 I have an Etrex Yellow and it always seems to read ~30ft off. Two questions: 1) 30' off compared to what? compared to someone else's GPS? You may not be the one with the problem. 2) What map datum is your eTrex set to? What datum is the other "reference" point set to? If you're at different datums, the same "numbers" may represent a point much further away. Most GeoCaching stuff is referenced to WGS84. The best way to check your GPS is to go the the Benchmarking page and find an adjusted (not scaled) mark and then see if your GPS agrees with the location. Most benchmarks are set to NAD83 but that's close enough to WGS84 to not worry about. Also, make sure you leave your GPS on long enough to fully acquire all the sats and download the almanac. You'll get a position with as few as 3 sats, but the more you can get the better. That's one of the reasons I advise getting rechargeable batteries - you'll leave the unit on longer since you won't worry about burning money. Quote Link to comment
+nincehelser Posted February 2, 2004 Share Posted February 2, 2004 That's one of the reasons I advise getting rechargeable batteries - you'll leave the unit on longer since you won't worry about burning money. That's because you already burned your money ahead of time. Sorry. Couldn't resist. George Quote Link to comment
+Karma Hunter Posted February 2, 2004 Share Posted February 2, 2004 The best way to check your GPS is to go the the Benchmarking page and find an adjusted (not scaled) mark and then see if your GPS agrees with the location. Most benchmarks are set to NAD83 but that's close enough to WGS84 to not worry about. True. And there's probably one you can visit within a few miles of your house. It's really the only way to have a "reference" point. I have an Etrex Yellow and it always seems to read ~30ft off. In the grand scheme of things (GPS things anyway), 30 feet is pretty good. Unless your unit always measures 30 feet off in a specific direction (and a benchmark or two will help you determine that), getting 30 feet of accuracy is pretty standard for the real world. Good observation skills are often more helpful than GPS readings when you're within 30 feet. For what it's worth, even the best units rarely get better than 10 feet of accuracy. Ten feet is about what I average with my Sportrak Map, but you may find using benchmarks that that's how close you're getting too. By the way, check your EPE (at least that's what it's called on Magellans) or Estimated Position Error at the times you take a reading. Your unit's reception varies constantly, so it will tell you how "accurate" (i.e.- within how many feet) its data is at any given time. This can mean that even if you show a distance of 30 feet to a waypoint, if your EPE is, for example, sixty feet, you're really only getting within sixty feet accurately. Perhaps I'm not explaining it well, but check for it in your manual. Also, be sure to read your manual to see how to hold your unit for best reception (vertical, horizontal, etc). It does make a difference. Quote Link to comment
+GeckoGeek Posted February 2, 2004 Share Posted February 2, 2004 That's because you already burned your money ahead of time. Fixed costs vs. variable costs. Sorry. Couldn't resist. Oh, you could have - but it wouldn't have been as much fun Quote Link to comment
+phinstr Posted February 3, 2004 Author Share Posted February 3, 2004 Thanks for all the help. I think I probably need to find a benchmark and check it out. FYI: Map Datum: WSG84 Units: Statute North Ref: Magnetic Variance: 018'E I dont know what all that means but that's what it is. I currently recide in Washington state N47'26.081 W120'20.060 Does the aforementioned information make sense for my location? Thanks again for your help. Now if I could only be the one to find the caches instead of my wife...... Quote Link to comment
+GeckoGeek Posted February 3, 2004 Share Posted February 3, 2004 Does the aforementioned information make sense for my location? I couldn't find a benchmark listed with those exact coordinates, so I assume that's your coordinates. The closest suitable disk is this one. Note that it says "location is ADJUSTED" in small print at the top of the datasheet. Avoid ones that say "location is SCALED" unless you want to calibrate your altimeter. Quote Link to comment
+phinstr Posted February 4, 2004 Author Share Posted February 4, 2004 GeckoGeek, I went to the Benchmark you suggested and my little yellow GPSr indicated I was off only 3.6ft. Close enough for government work. I guess the 30ft I am seeing is the combined error of my GPSr and those of the person hiding the cache. I cant complain about less than 4 ft. Thanks everyone for all your help Quote Link to comment
+GeckoGeek Posted February 4, 2004 Share Posted February 4, 2004 I cant complain about less than 4 ft. Especially since 00.001 minutes translates to around 6 feet. You're basically limited by the precision due to the number of digits on the GPS's display. You can't realistically ask for better then that. Quote Link to comment
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