Larry H Posted August 23, 2003 Share Posted August 23, 2003 I use a Garmin eTrex Venture with the lastest software upgrade. I was out this morning on a beach right on the ocean.It's accually an Island.There was clear unobstructed views of the sky and unlimited view to the horizon to the east and south.My GPS showed it had locked onto 10 sats including the WAAS sat and still it showed the accuracy only to be with in 26 feet. I disabled WAAS and it immediately showed accuracy to with in 10 feet. Enabled and disabled it a couple of times and each time it was more accurate with WASS disabled. Shouldn't it be more accurate with WAAS enabled? Or should WASS only be used to set a way point? I'm confused....... Quote Link to comment
+Brian - Team A.I. Posted August 23, 2003 Share Posted August 23, 2003 Have you updated your Venture with the latest ROM? The most recent 2 updates provide specifically the following which will hopefully improve your accuracy report.. Improved WAAS/EGNOS satellite selection algorithm to select the satellite with the most beneficial corrections given the unit's current position. A unit will not use a WAAS/EGNOS satellite if the unit's current position is outside of a given WAAS/EGNOS satellite's service volume. Brian Team A.I. Er, I guess I failed to read the FIRST line of your post before I went on that little bit of info-bleed. If you don't have 2.50 downloaded, you should probably upgrade. If so, disregard. Quote Link to comment
+TEAM 360 Posted August 23, 2003 Share Posted August 23, 2003 I use a Magellan Meridium Platinum. I have WAAS on all the time. I generally get 10-20' of accuracy. Many times I have seen 7' accuracy for short periods of time, but that's as low as I have seen it go. Then again, I am in Arizona, with no trees and hardly any cloud cover... The fact that you were near water might explain some inaccuracies in being able to receive a good lock, as you may have experienced erradic signal bounce. Quote Link to comment
+TEAM 360 Posted August 23, 2003 Share Posted August 23, 2003 Yea, and whatever Brian just said... Quote Link to comment
+Brian - Team A.I. Posted August 23, 2003 Share Posted August 23, 2003 quote:Originally posted by TEAM 360:Yea, and whatever Brian just said... Jeff, take the hat off man. It's restricting your blood flow. Brian Team A.I. Quote Link to comment
Larry H Posted August 23, 2003 Author Share Posted August 23, 2003 Yes Brian, I have the latest update installed. Team360, i didn't know about the water might be bouncing signals. I did notice a couple of tmes that the arrow turned around almost 160 degrees in the opposite direction of the cache i was hunting. My experance so far has been under tree cover so when i was on the beach and saw all those sats connected i was in awe. I know we're talking about only 16 feet here, i was just expecting more out in the open. Quote Link to comment
+EraSeek Posted August 23, 2003 Share Posted August 23, 2003 quote:Originally posted by Larry H:I use a Garmin eTrex Venture with the lastest software upgrade. I was out this morning on a beach right on the ocean.It's accually an Island.There was clear unobstructed views of the sky and unlimited view to the horizon to the east and south.My GPS showed it had locked onto 10 sats including the WAAS sat and still it showed the accuracy only to be with in 26 feet. I disabled WAAS and it immediately showed accuracy to with in 10 feet. Enabled and disabled it a couple of times and each time it was more accurate with WASS disabled. Shouldn't it be more accurate with WAAS enabled? Or should WASS only be used to set a way point? I'm confused....... Several thing you need to know. First, the first time you initiate WAAS it takes some time. Maybe 20 mins. It will cycle through the sats for a while. Once you see "D's" on most or all the sats bars you know that your WAAS is up and running. Second, you may see the WAAS sat bars up (what is it...35 and 47) but if you do not have little "D's" on any sat bars those sats are not being assisted by the WAAS system. Also, it may take up to 12 mins to download the almanac from the sats each time you turn your unit on. Also, and most important what you are seeing EPE or Accuracy Reading does NOT mean what you think it does. It is really just an estimate of how your unit thinks it is doing, not an accurate reading of your accuracy. First of all, it may not yet have all the data downloaded for the sats, or there is still a bad configuation of sats, or it is still figuring out things. Usually when you first bring up WAAS, your reading will go way up for a few minutes, then drop down lower that is was. So patience. But here is the kicker... when your accuracy reading goes up to say 40', what it is telling you is that your target should be within 40' of you 95% of the time. Now it may in fact be within 2' of you and so your accuracy reading is still correct although it is closer to the mark than before you turned on WAAS. Say your Accurcy reading says 15' with WAAS off and the target is 10' away from your input coordinates. Now you turn on WAAS and it says accuracy is 40' but you find that the target is now 2' away from your input coords. I have done this on benchmarks before. If you want your Accuracy Reading to be more accuracte in relation to reality, wait 5 mins. Once settled in you will find it more impressive. By the way, Accuracy Reading with WAAS on or off is generally about 40% further out that your true position. Say it says 18'. Your target is more in the order of 10' away....most of the time. "See the wonderous works of Providence! The uncertainty of human things!" Geo.Washington Quote Link to comment
Larry H Posted August 23, 2003 Author Share Posted August 23, 2003 Thanks for that explanation EraSeek,much appreciated. Quote Link to comment
+Tahoe Skier5000 Posted August 23, 2003 Share Posted August 23, 2003 All you will ever want to know about the WAAS system ----------------------------------------------------------- Garmin V Garmin III+ Quote Link to comment
+kevin917z Posted August 23, 2003 Share Posted August 23, 2003 i have a garmin too, it is a rino 120 i find that i have to let it "warm up" for about 15 minutes before it will hold an accuracy in the single digits, after it is on a while and has the almanac downloaded i can see it drop to 6-7 ft on average while caching in the woods, in thin trees or open ground i usually see an average of 4-5 feet, my best was 3 ft Quote Link to comment
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