+Xenox Posted November 19, 2007 Share Posted November 19, 2007 I have a question for you hardcore GPS users out there. I just purchased a Vista HCx to replace my old Magellan MAP 330 for geocaching. I've used the Vista HCx on nine caches so far, and so far, I'm concerned with its poor accuracy. With my MAP 330, I land within 10 feet of the cache and the reported position seldom drifts by more than 5 feet when I'm standing still. (The MAP 330 uses averaging to establish a better positional fix.) With the Vista HCx, the unit will wander from 0 feet to 35 feet away from the cache in different directions, even when I'm remaining perfectly still with ten strong satellite locks. This create a very large area over which I must hunt for each cache. Worse yet, the unit reports an accuracy of +/- 15 feet even when it's clearly far less accurate than that. As a test, I set a waypoint while sitting on my couch (near windows -- 8 strong "D" satellite locks) in my house and watched the Vista HCx's display without moving. The Vista HCx has reported that I'm anywhere from 7-35 feet away from where I set the waypoint, even though the accuracy was reported as +/- 13 feet. Another thing that confuses me is that the reported accuracy doesn't seem to improve when WAAS is enabled and all satellites are labeled with a "D" on the satellite screen (presumably for "differential" correction). Does this mean WAAS isn't helping to establish a better position, or that the effect of WAAS isn't taken into account when reporting accuracy? Additional questions: 1) What are the best options for increasing accuracy on the Vista HCx? Does WAAS significantly improve accuracy on the Vista? If so, why is it disabled by default? 2) Is there any way to improve the reliability of the "accuracy" number? I've read that some manufacturers only report a 50% reliable accuracy (i.e., the unit is only within the stated accuracy 50% of the time), which is pretty much useless. I'd much prefer a 95% reliable accuracy, so that I'd know how far I need to search when looking for a cache. 3) My wife likes to turn the unit off between caches. Is it better to leave it on? If so, how long does it take before the unit is running at optimum accuracy? (e.g., How often are WAAS updates sent? Does the unit use any kind of internal averaging to improve accuracy over time?) 4) The Visa HCx is far more sensitive to satellite signals than my MAP 330. Is there any value in intentionally attenuating the signals in an area with lots of reflections? I've read that signal reflection can add up to about 6 feet of additional error. Thanks in advance for any answers, advice or experience you wish to share! ---Gary Quote Link to comment
+Uncle T K Posted November 19, 2007 Share Posted November 19, 2007 3) My wife likes to turn the unit off between caches. Is it better to leave it on? If so, how long does it take before the unit is running at optimum accuracy? (e.g., How often are WAAS updates sent? Does the unit use any kind of internal averaging to improve accuracy over time? Do not turn your GPS off between caches Quote Link to comment
+JSWilson64 Posted November 19, 2007 Share Posted November 19, 2007 (edited) I wouldn't say your 330 was more accurate due to averaging, it just doesn't show small variations as much, just like if you had a thermometer that displayed the average temp. over the last 5 minutes instead of the instantaneous temp. Accuracy is a constant topic here - you might want to (re)read some of the FAQs. Keeping it on will definitely help accuracy. I'll repeat my mantra here: 10 meters is the given accuracy of civilian GPS (excluding surveying GPS with ground stations, post-processing, etc.). It doesn't matter what chipset you have, the owners of the satellites will tell you 10 meters is all they can promise. That's what makes Geocaching fun - if you could just walk right up to the cache with centimeter accuracy, where's the challenge? Edited November 19, 2007 by JSWilson64 Quote Link to comment
gratefulHIKE Posted November 19, 2007 Share Posted November 19, 2007 how long do you go between caches? If its like 10 minutes, then leave it on.....but more than a hour definitely turn it off And you have to remember.......no GPS in the world is going to put you exactly where the cache is, due to the reality of other people having other GPS's when they place the cache, and some people enjoy moving the cache's around after they find them.......I would say maybe 1/25 caches you would find that the GPS is RIGHT on the money (+/- 1-3ft) the vista hcx is definitely the best unit out there for the money, so I wouldnt even think of returning it.....I own a 60csx and a vista hcx, now my 60 sits on the shelf because I find the vista to be much more stable when it comes to signal variance Quote Link to comment
+Xenox Posted November 19, 2007 Author Share Posted November 19, 2007 I'll repeat my mantra here: 10 meters is the given accuracy of civilian GPS (excluding surveying GPS with ground stations, post-processing, etc.). It doesn't matter what chipset you have, the owners of the satellites will tell you 10 meters is all they can promise. That's what makes Geocaching fun - if you could just walk right up to the cache with centimeter accuracy, where's the challenge? The specifications section of my manual states: Accuracy: GPS: 10 meters (33 feet) 95% typical [...] DGPS: 3 meters (10 feet) 95% typical* *Wide Area Augmentation System (WAAS) accuracy in North America Therefore, with WAAS enabled (which is a collection of ground stations performing post-processing), Garmin says I should expect 10-foot accuracy 95% of the time. This was my experience with my MAP 330. I don't expect centimeter accuracy, but a 70-foot diameter circle (especially one that I don't know the center of) is much too big when hunting for micro-caches. Please keep in mind that I'm not criticizing the accuracy of the GPS system. I've used it for years, and have reasonable expectations. What I'm doing is questioning the accuracy of the Vista HCx in particular, because it appears to be much worse than another inexpensive consumer unit I've owned for nearly a decade. Quote Link to comment
+Miragee Posted November 19, 2007 Share Posted November 19, 2007 I have a Vista HCx and get accuracy of 10' in areas with an unobstructed sky. Since I don't hunt urban micros, I don't know what the accuracy would be in the presence of high buildings . . . Seems to me I remember when the Vista HCx first came out there were problems with accuracy on some units. Do a Search of the Forums for posts about six months ago to see if you can find those discussions. Garmin Customer Support is very responsive, so you might call them (early in the morning when the hold time is less) to see what they say. Quote Link to comment
+Xenox Posted November 19, 2007 Author Share Posted November 19, 2007 Quick Update: My Vista HCx was running version 2.30 of the firmware. I've updated to 2.40 (the latest) and will perform additional testing with the new firmware. My initial impressions are that the accuracy numbers reported by version 2.40 are more realistic. I see numbers like 195 ft. accuracy when inside of buildings now instead of 35 ft. However, this could be coincidence. I will test the new firmware outdoors with a clear sky and follow up to this thread. Quote Link to comment
+scouter72 Posted December 2, 2007 Share Posted December 2, 2007 Quick Update: My Vista HCx was running version 2.30 of the firmware. I've updated to 2.40 (the latest) and will perform additional testing with the new firmware. My initial impressions are that the accuracy numbers reported by version 2.40 are more realistic. I see numbers like 195 ft. accuracy when inside of buildings now instead of 35 ft. However, this could be coincidence. I will test the new firmware outdoors with a clear sky and follow up to this thread. My Vista HCx is on 2.4 and am experiencing the same things you are. I wrote to Garmin support today to see what they say and may be sending mine back. This is not acceptable for my use and far less accurate than my Vista C that I just sold to get this one. I have been with a friend on some recent Geocaching and my new Vista HCx is always 20-30 feet off where before we had both been on together. Quote Link to comment
+Klemmer Posted December 2, 2007 Share Posted December 2, 2007 The newer chip-sets in these units (SiRFstar III or equivalent) are much more sensitive than older receiver technology. As a result, IMHO, they NEED averaging to be useful. When you are inside buildings or under heavy tree cover, don't expect the positions to be realistic. Too much signal reflection makes for a mess. If the unit doesn't average, and it is as bad as it sounds like, I would return it. Quote Link to comment
GeoBobC Posted December 2, 2007 Share Posted December 2, 2007 I have an opinion about this (don't we all?) I recently bought a Vista HCX to complement my 60Cx. I returned it after one week of disappointing results. My primary complaint was the accuracy of the Vista in recording track logs. I use my GPS units to record tracks so I can create custom maps of trails. I've found it typically takes about four trips to get a cluster of trails from which I manually draw a trail through the center of the clustered tracks. Having recorded some trail tracks more than 10 times with my 60Cx, the Vista tracks from my week of testing often fell completely outside of the cluster of tracks recorded on my 60Cx. The Vista displayed accuracy estimates very similar to the 60Cx, but the results did not match. The tracks often missed turns in the trails, and often went off by 60 feet or more. One other interesting note: it appears that the 60Cx (Sirf chip) tracks have a slightly different bias than the Vista (MTK chip) tracks. In other words, the 60Cx tracks were, for the most part, consistently west and south of the Vista tracks. I can't conclude that is true with statistical certainty, but it looks that way to me. I concluded that the Sirf (60cx series) chip is slightly more accurate than the MTK, in my tests under heavily canopied trails. However, I do wonder if the perceived bias in the position calculations of the two units is causing some difficulty in locating a cache. In other words, if I hid a cache with my 60Cx, and tried to locate it with the Vista, would there be a slight difference in their locations? I don't believe that would be the case, but it might be. I attribute the differences in track logs between the Sirf and MTK chip sets to slightly improved accuracy in the Sirf, and perhaps slightly faster processing: as I make a turn on the trail, the Sirf chip responds more quickly. I could see the directional arrow turn immediately on my 60Cx, while the directional arrow on the Vista took a few seconds longer to display a change in direction. Quote Link to comment
SiliconFiend Posted December 3, 2007 Share Posted December 3, 2007 I have an opinion about this (don't we all?) I recently bought a Vista HCX to complement my 60Cx. I returned it after one week of disappointing results. My primary complaint was the accuracy of the Vista in recording track logs. I use my GPS units to record tracks so I can create custom maps of trails. I've found it typically takes about four trips to get a cluster of trails from which I manually draw a trail through the center of the clustered tracks. Having recorded some trail tracks more than 10 times with my 60Cx, the Vista tracks from my week of testing often fell completely outside of the cluster of tracks recorded on my 60Cx. The Vista displayed accuracy estimates very similar to the 60Cx, but the results did not match. The tracks often missed turns in the trails, and often went off by 60 feet or more. One other interesting note: it appears that the 60Cx (Sirf chip) tracks have a slightly different bias than the Vista (MTK chip) tracks. In other words, the 60Cx tracks were, for the most part, consistently west and south of the Vista tracks. I can't conclude that is true with statistical certainty, but it looks that way to me. I concluded that the Sirf (60cx series) chip is slightly more accurate than the MTK, in my tests under heavily canopied trails. However, I do wonder if the perceived bias in the position calculations of the two units is causing some difficulty in locating a cache. In other words, if I hid a cache with my 60Cx, and tried to locate it with the Vista, would there be a slight difference in their locations? I don't believe that would be the case, but it might be. I attribute the differences in track logs between the Sirf and MTK chip sets to slightly improved accuracy in the Sirf, and perhaps slightly faster processing: as I make a turn on the trail, the Sirf chip responds more quickly. I could see the directional arrow turn immediately on my 60Cx, while the directional arrow on the Vista took a few seconds longer to display a change in direction. I wonder if there's something slightly off with your Vista HCx. I cart mine around everywhere and when I look at the track logs, there is very tight correlation between the outbound and inbound tracks, and also between multiple trips. Of course, there's the occasional outlier, but in general it's very good. Quote Link to comment
GeoBobC Posted December 3, 2007 Share Posted December 3, 2007 I suspect some variation is inherent in every unit. If you hold two identical units side by side, you don't always get the exact locations displayed. The amount of deviation I saw with the Vista was enough to convince me to stick with the 60 series units. I wish it weren't so, and perhaps I'll retry at a future date with another Vista. I wonder if Garmin will update the MTK chipsets like they have with the Sirf chips? Quote Link to comment
+pigpen4x4 Posted December 4, 2007 Share Posted December 4, 2007 I've been a proponent of the Vista HCx since I got one and was very pleased with it. Until I set out a new hide this weekend. I always mark, average (a lot) the have the GPS walk me back to it. The Vista HCx would never get me "there". Always at least 20' difference. This was very frustrating to me, so I got out the 60CSx, let it settle, and went through it again. Bingo, the results I'm used to. I'm not knocking the HCx, yet. But I will be looking into what I can do to make it better. PP4x4 Quote Link to comment
+hogrod Posted December 4, 2007 Share Posted December 4, 2007 I wonder if Garmin will update the MTK chipsets like they have with the Sirf chips? I'm probably mistaken, but wasn't there an update available via the webupdater for the new H series chipset? Quote Link to comment
+JohnTee Posted December 4, 2007 Share Posted December 4, 2007 Got my new Vista HCx a little over a week ago; upgrade from an eTrex Legend. I can't believe the accuracy! Sitting in my living room with the nearest window 15' away to the east, a 8' front porch and an unfinished room overhead. My Legend might see a satellite or two with a VERY weak signal and never get a lock. I could put a USB extension on the Legend and set it in one of the window sills and may occasionally get enough signal to get a poor fix. Sitting in the same place with the Vista I'm getting eight satellites and 15' EPE. Coord's shown on the satellite page don't jump at all. Sitting at my desktop computer in the kitchen, which is behind the wall where I'm sitting in the living room, with the nearest window about 15' away to the west, a ten foot porch and the same unfinished room overhead, and I'm getting good satellites with 26' EPE, no wavering of signals. The Legend would NEVER have seen a satellite from in there. Last night, sitting in the bleachers near the east end of a concrete gym (concrete roof arches, I don't know the roof composition) and rows of windows on the long north and south walls above those bleachers. I was getting satellites with a 46' EPE. The Legend might have seen a satellite every now and then, but never gotten a lock. Sitting in an office, inside a hanger with sheet metal walls and roof; a few skylights. I had something like 5 or 6 satellites and an 86' EPE. I might have gotten a glimpse or two of a satellite with my Legend. Coord's didn't jump around. Now, to out in the wild . . . After four caches, I am finding that the Vista seems to be putting me 12-20' away from caches with good signal lock. Naturally, between the inherent error from EPE between two different units and potentially lower sensitivity of the hiders GPSr . . . it may well be I'm close to the correct coordinates and the hider was not . . . I have not had my position jump around at all. I was seeing that with my Legend on multiple occasions, especailly with heavy cover. Standing in one spot it might show me at GZ, then suddenly GZ was 70' to the south, then all of a sudden 15' to the west. Another day I had it out walking on a local path to track our distance and speed. With light to moderate tree cover, it was doing O.K., until it came time to turn around and walk back. After doing so, I noticed the track was showing a jog several hundred feet perpendicular off the trail that we had not made. Screwed up the odometer and average speed of the rest of the walk. As I get more caching in with my Vista, I'll better be able to assess its accuracy in the wild. JohnTee Quote Link to comment
+YeOleImposter Posted December 5, 2007 Share Posted December 5, 2007 Got my new Vista HCx a little over a week ago; upgrade from an eTrex Legend. I can't believe the accuracy! Sitting in my living room with the nearest window 15' away to the east, a 8' front porch and an unfinished room overhead. My Legend might see a satellite or two with a VERY weak signal and never get a lock. I could put a USB extension on the Legend and set it in one of the window sills and may occasionally get enough signal to get a poor fix. Sitting in the same place with the Vista I'm getting eight satellites and 15' EPE. Coord's shown on the satellite page don't jump at all. Sitting at my desktop computer in the kitchen, which is behind the wall where I'm sitting in the living room, with the nearest window about 15' away to the west, a ten foot porch and the same unfinished room overhead, and I'm getting good satellites with 26' EPE, no wavering of signals. The Legend would NEVER have seen a satellite from in there. Last night, sitting in the bleachers near the east end of a concrete gym (concrete roof arches, I don't know the roof composition) and rows of windows on the long north and south walls above those bleachers. I was getting satellites with a 46' EPE. The Legend might have seen a satellite every now and then, but never gotten a lock. Sitting in an office, inside a hanger with sheet metal walls and roof; a few skylights. I had something like 5 or 6 satellites and an 86' EPE. I might have gotten a glimpse or two of a satellite with my Legend. Coord's didn't jump around. Now, to out in the wild . . . After four caches, I am finding that the Vista seems to be putting me 12-20' away from caches with good signal lock. Naturally, between the inherent error from EPE between two different units and potentially lower sensitivity of the hiders GPSr . . . it may well be I'm close to the correct coordinates and the hider was not . . . I have not had my position jump around at all. I was seeing that with my Legend on multiple occasions, especailly with heavy cover. Standing in one spot it might show me at GZ, then suddenly GZ was 70' to the south, then all of a sudden 15' to the west. Another day I had it out walking on a local path to track our distance and speed. With light to moderate tree cover, it was doing O.K., until it came time to turn around and walk back. After doing so, I noticed the track was showing a jog several hundred feet perpendicular off the trail that we had not made. Screwed up the odometer and average speed of the rest of the walk. As I get more caching in with my Vista, I'll better be able to assess its accuracy in the wild. JohnTee Cannot be sure, but I was having problem with a new Vista HCX until I turned off the compass (my new 60csx has the exact same problem). Since you are saying it does not jump around, I am guessing you have the magnetic compass turned on. Try turning it off, sure it will jump, but as long as you ignore the arrow and go N,S,E,orW it will work just like your Legend and put you at GZ. If you really want to use the magnetic compass, then I suggest calibrating it each day before you go out caching, away from your vehicle. Quote Link to comment
+JohnTee Posted December 5, 2007 Share Posted December 5, 2007 Cannot be sure, but I was having problem with a new Vista HCX until I turned off the compass (my new 60csx has the exact same problem). Since you are saying it does not jump around, I am guessing you have the magnetic compass turned on. Try turning it off, sure it will jump, but as long as you ignore the arrow and go N,S,E,orW it will work just like your Legend and put you at GZ. If you really want to use the magnetic compass, then I suggest calibrating it each day before you go out caching, away from your vehicle. Hi 'YeOleImposter', Actually, I've been using my GPSr with the compass 'Off' to save battery life. In other news . . . Yesterday I did a walk along the walking path mentioned above. I waypointed three caches I have along there, allowing the GPSr to average 50 sets of coordinates each time. On the way back I remembered to try navigating to #2 . . . ended up about some 15' away from the original set, done 15 minutes before. Shot another set. On the way back to #1, set up navigation and went STRAIGHT to it. Pretty much clear sky both places, with a bit of a tree line to the west of #2. John Quote Link to comment
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