GPS's and their Accuracy

[+infiniteMPG]

There are tons of different GPSr units out there and it sometimes seems like those with the most "play money" (i.e. can afford the most accurate GPSr) have the biggest advantage when caching. What GPS do you own and what do you feel are the biggest advantages/disadvantages of it?

 

I have a Garmin GPS MAP60C (and wish I had the CSX as I have City Navigator and are limited on the mapsets I can load). It is okay but seems to bounce a lot. A friend has a Magellin and states that he can load a bunch of geocaching data on his GPSr. I am limited to the text I can load with a cache and rely on my Palm TX to get me by.

 

And also do you feel at a disadvantage when caching in a group and someone has a more precise read on the hide? Do you think well tuned geosenses make up for GPSr inaccuracies?

[+briansnat]

There is little difference in accuracy between units. There is a difference in sensitivity.

 

Even if your unit was more accurate than your caching partners', it would not be an advantage because there is no guarantee that the cache's coordinates are on the money.

[+StarBrand]

Agree with briansnat.

 

Very little difference in the accuracy of any of the handheld units except those with WAAS turned on. But that won't help with finding the cache because you have no idea if the hider used WAAS or had good geometry of satellites when they hid it.

 

Some have better antennas, so you can hold the signal better. And some have high sensitivity chips but that does not improve accuracy, only the abilty to find and hold a signal. Even then it makes little or no difference out on flat terrain.

 

So wether you spend $80 for the old yellow etrex or $600 on a new Colorado unit - the only real difference is in the little bells and whistles in the form of accessories. None of them give you any advntage in accuracy to find caches.

[+NorthWes]

The accuracy of the cache hider's GPS unit is my first concern! More correctly... the effort made by the cache hider to ensure the best possible set of coordinates for their cache through averaging, checking back to the location at different times, etc. I know some hiders believe in 'loose' coordinates - but accurate coordinates reduce the impact made on a cache site by less-careful cache hunters when searching, which is of real consideration when placing a cache in such a way as to limit its environmental impact. No one wins when a cache site is torn apart (in part because of inaccurate coordinates) - especially geocaching's overall reputation.

 

Now - I feel the same frustration everyone else does on those days when my Garmin eTrex Vista won't settle down and give me 'good' satellite lock. I cache with friends who have more expensive Garmins and Magellans, as well as less expensive units. We kid around that the different brands all seem to have about a 20' offset, even when they 'zero out'! The fastest finder is inevitably the one of us who's most attuned to the hide possibilities at the final site. If it's a micro, there's some of us who're more attuned to that genre of hide. Ammocans? I've missed 'em close up - even when they're under the 'usual pile of sticks'! Even the angle of approach to a hide can benefit one over the other, regardless of accuracy.

 

'Geosense' is often best described as 'how would I hide something here?' and that seems to make for the speediest finder. My wife says ladies will always find stuff faster than their husbands, as they're more used to looking 'under' stuff for what's missing (versus us guys, who plaintitively wail 'Have you seen...???').

[Mag Magician]

We find with the Blue Etrexes, that turning off the WAAS and setting a goto will result in being within 5 feet of a well placed cache, 9 times out of 10

[+boda]

I've compared my gps against others of different brands and/or models. I have seldom seen any two units that show the exact same coordinates when placed at the same spot. We all found caches, however; so the differences weren't a problem.

 

Mine is always right on the money, but the caches aren't in the right place.

[+infiniteMPG]

We find with the Blue Etrexes, that turning off the WAAS and setting a goto will result in being within 5 feet of a well placed cache, 9 times out of 10

Got my attention with that comment on WAAS. My GPS MAP60C had the WAAS disabled and it took more then 5 minutes for it to lock on when powered up. When seeking a cache it would bounce all over. I mean take us in one direction, 40 feet, 20 feet, then all of a sudden turn 180-degrees and state 65-feet. Then head that way and when you get close swing around 90-degrees and state you're 50-feet away. Really frustrating. When we enable WAAS it was locked on within 30 seconds of powering up (and in the garage still) and it seemed to hold direction and distance closer.

 

So I guess I need to ask....

 

WAAS enabled or disabled when caching????

[+infiniteMPG]

Mine is always right on the money, but the caches aren't in the right place.

Hehehehe.... had a friend that dumped his eTrax Vitsa and bought a MAP 60CSX and then was complaining that caches weren't at the right place. Well, if the persin hiding it doesn't have a high end GPSr then the coords on the webpage aren't correct. What tickles me is people that enter log entries complaining that the cache was 10-feet off from the coords. 10 FEET??? I'd be really happy with 10 feet!

[+Stargazer22]

We have 2 units, a GPSMAP 76Csx and a Vista Hcx.

Both units seem to have about the same accuracy. Despite the claims of high sensitivity on the Vista Hcx, it seems to lose signal and lock more often than the 76Csx.

We've also noticed that the Vista Hcx has more of a tendency to do exactly what you were describing about pointing 50 feet in one direction, then once you move 5 or 10 feet, it flips around and points 45 or 50 feet in the opposite direction. The 76Csx is much more stable in this respect and typically holds a consistent indication.

 

We normally operate both units with WAAS turned on.

As others have described in the GPS and units forum, the odometer on the Hcx does not work well when moving at slow (under 2mph) speeds. One of the recent hikes we made was just under 7 miles. When I plotted our hike on Google Earth, I came up with real close to 7 miles. Our 76Csx indicated we had gone 6.8 miles, close enough. However the odometer on the Vista Hcx showed only 2.2 miles, with most of the time noted as not moving.

We have tried different settings on the unit but it doesn't seem to make any difference. I made sure I have the latest software update installed from the Garmin website, too.

 

Whenever we cache, my wife takes one unit and I take the other and we see where we wind up. You would think that we would usually find the cache between where the two of us are looking, however, what usually happens is that one unit indicates a position that is considerably closer to the cache than the other. And it's not always the same one on the same day. Even hides that were placed on the same day by the same hider will sometimes be found close to where one unit indicates, while the other shows 15-20 feet in another direction.

On the next hide by that same hider, the other unit may have a closer indication.

The differences are not consistent. I would expect that's probably due to how the hider marked his coordinates when hiding, or the accuracy of his unit that day, etc...

 

As far as overall accuracy though, they are both usually pretty much in the same ball park.

[Keystone]

Moving thread from the Geocaching Topics forum to the GPS Units and Software forum.

[yatesDELTA]

Mine is always right on the money, but the caches aren't in the right place.

Hehehehe.... had a friend that dumped his eTrax Vitsa and bought a MAP 60CSX and then was complaining that caches weren't at the right place. Well, if the persin hiding it doesn't have a high end GPSr then the coords on the webpage aren't correct. What tickles me is people that enter log entries complaining that the cache was 10-feet off from the coords. 10 FEET??? I'd be really happy with 10 feet!

 

I have a garmin etrex yellow

 

and the signal acuracy is very rarely better than 20ft so unless other GPSrs have a much better accuracy than this them complaints are just stupid really

[+infiniteMPG]

Moving thread from the Geocaching Topics forum to the GPS Units and Software forum.

Ooops, this orginally started to be a topic if geosenses beat out an accurate GPSr.... guess we drifted. Thanks!

[+infiniteMPG]

We've also noticed that the Vista Hcx has more of a tendency to do exactly what you were describing about pointing 50 feet in one direction, then once you move 5 or 10 feet, it flips around and points 45 or 50 feet in the opposite direction. The 76Csx is much more stable in this respect and typically holds a consistent indication.

Another problem I get with the 60C is that the direction arrow may be pointing behind me or way off to one side and as I'm walking the numbers are going 75, 50, 25.... etc. So I know I'm heading in the correct direction as the distance is dropping but the arrow may be pointing behind me. Often we just click over and look at the coords rather then the "go to" stuff when it's acting like that.

 

Do you get this stuff with the 76Csx?

[+admo1972]

Another problem I get with the 60C is that the direction arrow may be pointing behind me or way off to one side and as I'm walking the numbers are going 75, 50, 25.... etc. So I know I'm heading in the correct direction as the distance is dropping but the arrow may be pointing behind me. Often we just click over and look at the coords rather then the "go to" stuff when it's acting like that.

 

A few things come to mind:

 

At those distances you are getting quite close to the cache. It can often be quite normal for the directional arrow to appear erratic once you begin to get close to the cache.

 

Your unit doesn't have an electronic compass, so you need to be moving fairly quickly and ideally in a straight line for the pointer to be accurate. If you stop, or move too slowly, the pointer is useless. And it gets worse the worse the reception is, as the unit is even less certain of your true location, so as it makes it's best guess where you are second to second, it also thinks you are "moving" to these new locations which means it also believes you are travelin gin directions quite contrary to your actual walking direction.

 

I hope this helps, but it may not...

[+infiniteMPG]

At those distances you are getting quite close to the cache. It can often be quite normal for the directional arrow to appear erratic once you begin to get close to the cache.

Yup, we noticed it's when we're close but sometimes when we move further away and the re-apporach, the arrow seems to lock in one direction and I can walk in circles and if it was point back behind me it will stay behind me even when doing 360-degrees.

 

Your unit doesn't have an electronic compass, so you need to be moving fairly quickly and ideally in a straight line for the pointer to be accurate.

We also have an old eTrek Vista and it has an electric compass in it and there's a big difference between the two in that respect. In fact I really like the joystick toggle on the Vista as I think Garmin really tripped over there feet with the big rocker pad on the 60C. You try to move left so you push left and the cursor moves left, you push left and the cursor moves left, you push left and the cursor moves UP! HUH???? Does the 76Csx have the same mushy input method?

 

Yes, it all helps

[Mag Magician]

We find with the Blue Etrexes, that turning off the WAAS and setting a goto will result in being within 5 feet of a well placed cache, 9 times out of 10

Got my attention with that comment on WAAS. My GPS MAP60C had the WAAS disabled and it took more then 5 minutes for it to lock on when powered up. When seeking a cache it would bounce all over. I mean take us in one direction, 40 feet, 20 feet, then all of a sudden turn 180-degrees and state 65-feet. Then head that way and when you get close swing around 90-degrees and state you're 50-feet away. Really frustrating. When we enable WAAS it was locked on within 30 seconds of powering up (and in the garage still) and it seemed to hold direction and distance closer.

 

So I guess I need to ask....

 

WAAS enabled or disabled when caching????

 

When you have a weak (or no) signal from the WAAS satellite, as in the area we normally cache, turn it off. If you can get a good signal, then definitely turn it back on. Here in the Near North of Ontario, we can only get the Atlantic WAAS satellite, and that is on a good day. Turning WAAS off lets the GPSr use less energy and concentrates on the available satellites instead of wasting time and battery power looking for something it can't get.

Edited February 14, 2008 by Team Magic

[+Stargazer22]

We've also noticed that the Vista Hcx has more of a tendency to do exactly what you were describing about pointing 50 feet in one direction, then once you move 5 or 10 feet, it flips around and points 45 or 50 feet in the opposite direction. The 76Csx is much more stable in this respect and typically holds a consistent indication.

Another problem I get with the 60C is that the direction arrow may be pointing behind me or way off to one side and as I'm walking the numbers are going 75, 50, 25.... etc. So I know I'm heading in the correct direction as the distance is dropping but the arrow may be pointing behind me. Often we just click over and look at the coords rather then the "go to" stuff when it's acting like that.

 

Do you get this stuff with the 76Csx?

 

Yes, sometimes, but we have seen that happen more often on the Vista Hcx. Sometimes calibrating the compass helps. Even if it was calibrated earlier and is still on the same set of batteries. The 76Csx seems to not need the calibration as often. Sometimes calibrating doesn't help at all.

 

One method we have used to help out with this is to look on the map page of the unit to see where it indicates the cache is in relation to the road or whatever else is on the page as a landmark. If it looks like it's about 150 feet ahead and on the right side of the road, that's where we head to look. Regardless of what the arrow says at that point. Then watch the distance numbers go down as you have noted.

Looking ahead about 150-200 feet and trying to see a good spot for a cache seems to help zero in on the right area while taking the arrow with a grain of salt. We don't usually have to do that for the 76Csx.

 

So I guess that's the answer to your other question on the OP. Yes, geosenses help to make up for areas where GPSr performance is a little erratic sometimes. I have noticed over the last few months as we have gained more experience, I am getting better about picking out the cache location from a couple of hundred feet away as we come in.

 

Another method that sometimes helps is to stand off to one side of the cache about 75 feet and look to see where the arrow points, taking a landmark like a tree for an imaginary line. Then go off about 90 degrees to about 75 feet out again and look for another landmark for a line. Where the two lines cross is pretty close to where we will find the cache, usually. Sort of like crude triangulation in a way.

This can also help when using the 76Csx as it will usually put us in a smaller area to search. It seems to help minimize the 'fringe' areas.

 

The post from admo1972 noting that when you get that close to the cache, the arrow will seem less accurate is a good observation. (sorry, I couldn't figure out how to get a 2nd quote on the post). Think of it this way, if you have only about 20 feet accuracy, when you are 200 feet away, that +/- 20 feet is an error of 40 feet. This give you a triangle that is 200 feet long on the apex, with the base being 40 feet wide. When you get within 50 feet, you now have a triange that is only 50 feet long to the apex, and still 40 feet wide at the base. That is a much wider angle to represent the error. So, as you approach, the error becomes a more significant factor with each step. That's why once you get within about 20 to 30 feet from the cache, you're almost best to just put the unit in your pocket and use the Geosenses. Ohterwise, you wind up just chasing the error around and around and around.....doing the drunken bee dance!

[+Stargazer22]

In fact I really like the joystick toggle on the Vista as I think Garmin really tripped over there feet with the big rocker pad on the 60C. You try to move left so you push left and the cursor moves left, you push left and the cursor moves left, you push left and the cursor moves UP! HUH???? Does the 76Csx have the same mushy input method?

 

 

Yes, much to my chagrin sometimes, I get this same thing on my 76Csx as well. The rocker pad is not nearly as good as the joystick on the Vista Hcx for entry. Whenever we hand enter a set of coordinates, it's always much faster to enter them on the Vista Hcx. Same thing for menu selections and etc...

The rocker pad is not as easy to use as the joystick, and sometimes goes in an unexpected direction.

[+ollave]

At those distances you are getting quite close to the cache. It can often be quite normal for the directional arrow to appear erratic once you begin to get close to the cache.

Definitely agree: both when you're within the accuracy limit of the GPS system (not merely the receiver, but the whole system) or when you are moving too slowly the arrow won't be very helpful.

 

Today I was seeking a cache that required scrabbling over loose rock on a steep slope. The GPSr had no idea what direction I was traveling: I was moving too slowly. So the arrow was moving erratically, as was what the GPSr indicated was "north".

 

The GPSr did know was where it was and the distance to the cache coordinates, so rather than follow the arrow I just kept moving in the direction I'd been going and watched the distance count down. Once the GPSr claimed it was within 8m of the cache I saw the obvious location (too easy for a difficulty 3 cache, I'd have thought) and yup, there it was.

 

Other times when I'm moving faster the GPSr can appear to be erratic. Stopping moving for a minute or two seems to help (dunno about the science of this) and also moving /back/ from the cache location and circling well outside the claimed accuracy of the GPSr (15-20m works well for me) can help pin down which tree, pile of rocks, or pile of sticks I should be looking at.

 

Of course, if all else fails, turn off the GPSr and think "Now, where would I hide a cache?". Today I had one multi-cache with both its waypoint and GZ coordinates off by quite a way, yet the (fourth ...) "obvious" place was indeed the right place.

 

Persistence pays off too. :-)

 

(My GPSr? A lowly Geko 201. It works, although I'm seeing the attraction of going paperless ...)

[+admo1972]

Of course, if all else fails, turn off the GPSr and think "Now, where would I hide a cache?". Today I had one multi-cache with both its waypoint and GZ coordinates off by quite a way, yet the (fourth ...) "obvious" place was indeed the right place.

 

I agree with the idea of ignoring the GPSr at some point and just searching with eyes, hands, etc. But I don't turn it off. I find the longer it is on, the better it gets a signal, or quicker to get a stronger one. So I just find a nice spot to lay the GPS down (ideally on top of a prevelant stump or big branch, so I can find it again). That way, I can search the area with no GPS in hand, but head back to it to see it's reading. Too often I think I'm at a GZ, so I search and find nothing, only to check back with the GPS, and it has an accuracy of 9 feet, but it pointing 30 feet in another direction, which turns out to be the actual GZ area.

[+apersson850]

That's exactly the same procedure I use. Works very well if you have a unit with a magnetic compass.

[TJJSDJ]

I have a Magellan explorist 210 and it seems to get me where I need to go.....BUT, does anybody know how to laod more detailed maps on it?