Picking out a new GPS (400t probs)

[+Trashburg]

Well a couple months back best buy was running a deal on the colorado 400t's for 280 bucks so I grabbed one because I really wanted to get into geocaching. I ended up goin thru 3 of them that day trying to find one that was even remotely accurate. The first two I got after calibration and updates were only accurate to 100ft at best. The third and last one they had was accurate to 46 feet. I now have a year subscription to geocaching.com for the use of the paperless uploading function that my 400t had. I would really like that in my next unit as well. Any suggestions on what I should replace it with? I'd even consider gettin another one long as it was accurate. I'm wondering if it was my user error but I kept finding reviews with the same problem online. Anyone care to help?

-R3

[+StarBrand]

How are you measuring the "accuracy"?

 

Did you load up the latest firmware?

 

Was WAAS turned on?

 

The Colorado is a highly accurate unit with the newest firmware.

[+bittsen]

How are you measuring the "accuracy"?

 

Did you load up the latest firmware?

 

Was WAAS turned on?

 

The Colorado is a highly accurate unit with the newest firmware.

 

I concur. As much as I am disappointed with some of the bugs the 400T has had, I have never been disappointed with its accuracy.

Turn on WAAS and turn off the compass. The unit should be very accurate at that point.

I have accuracy down to 6 feet out in the open.

[+Trashburg]

It was updated with the latest firmware. The waas ....was on but didnt seem to make a difference. Compass was on too. I would mark a way point then walk away a while then go back to it and it was WAY OFF. I also tried marking intersections of streets and walking to them. Again way off. Bummed me out because I got such a good deal on it. I still have the receipts and would try and would get another if i could work out that problem.

Edited July 28, 2009 by Trashburg

[+Chris CA]

It was updated with the latest firmware. The waas ....was on but didnt seem to make a difference. Compass was on too. I would mark a way point then walk away a while then go back to it and it was WAY OFF. I also tried marking intersections of streets and walking to them. Again way off. Bummed me out because I got such a good deal on it. I still have the receipts and would try and would get another if i could work out that problem.

What was the error reading on the GPS?

[+bittsen]

It was updated with the latest firmware. The waas ....was on but didnt seem to make a difference. Compass was on too. I would mark a way point then walk away a while then go back to it and it was WAY OFF. I also tried marking intersections of streets and walking to them. Again way off. Bummed me out because I got such a good deal on it. I still have the receipts and would try and would get another if i could work out that problem.

 

Try it with the compass off

[+Trashburg]

10ft if i remember right and i returned it and am trying to get best buy to price match it online at the moment. So no luck in trying it with the compass off. How would that affect it if you dont mind me asking.

[+Styk]

If it's only a couple months old why wouldn't you use the Garmin warranty? Turning the compass off will help with navigating back to the waypoint as the compass has to be held fairly level and are known to be jumpy shall I say. while the unit is high sensitvity, accuracy in the city may not be as good as out in the open. With the latest averaging option and with a good satellite pattern, if you stop and wait a minute before marking the waypoint you will probably see an decrease in the waypoint as originally marked and after navigating back to it. Another way to check it is tgo walk a distance in the open with it and another unit and then compare the tracks in Mapsource.

[+twolpert]

Especially in challenging reception conditions (heavy tree cover, tall buildings, etc.), the compass tends to confuse new Colorado users when trying to approach a waypoint or cache. As you near the marked point, the "pointer" (which tells you which direction to go to reach the marked point) tends to swing in circles. This makes you want to move in different directions, which inhibits your ability to actually reach the marked point. The unit does not do this (or, at least, does not do it nearly as much) with the compass disabled.

 

I agree with the previous posts regarding the general accuracy of the Colorado. I own a 400t and it works fine. A couple of suggestions for you:

 

1) When starting out on your test run: Turn the unit on, stand still, wait for it to acquire a lock, and then wait for the EPE to drop to an acceptable level (say 15 to 20 feet). Then, if you want to bow to an extra level of paranoia, power cycle the unit. Some earlier firmware versions tended to favor a fast fix over accuracy -- and it took a while to get to the correct position even AFTER the EPE dropped to an acceptable level. The power cycle puts you in the correct location immediately. (This is a quirk. No idea if it's still true with the latest firmware.)

 

2) When marking a waypoint for your repeatability experiment: Walk to the point in question. Before actually marking the waypoint, stand still and hold the unit still for at least 90 seconds. This allows the unit to "settle" so that the marked point will be as accurate as the current EPE allows. (The Colorado tends to "predict" your position a bit when you are moving. The wait before marking allows the unit to work that out of its system.)

 

3) If you have new enough firmware, use the averaging function for at least 5 minutes.

 

4) When you approach the waypoint to test repeatability: Get close, then stand still and let the unit settle. Then and only then, try to approach ground zero directly. You may need to let the unit settle repeatedly as you approach the marked point to get maximum reliability.

 

Although some of this is based on Colorado quirks, most of it applies to all handheld consumer-grade GPSrs. Point is that you're liable to have the same issues with another model. So try to work it out with the Colorado

[+Trashburg]

I figured I was just a noob lol. Well I got bb to price match it so I should have a new one inside of two weeks and I'll let you guys know how nuts I am after the fact. Thanks for all the help. You guys are seriously ontop of things.

-R3

[+Chris CA]

nm

Edited July 28, 2009 by chrisca

[+cummings66]

If I understand your complaint correctly you're saying that the GPS is inaccurate because it won't bring you back to the same spot each time?

 

If so, that's a user perception issue. Suppose the reading you took was 10 off to the North, so you go back to it and now it's spot on so you're 10 feet south of your original spot. Or suppose it's now off 10 feet to the south and now you'll find you're off 20 feet because the first time it was 10 feet north of true.

 

A GPS will not bring you to the same spot each time, it can get you close but that's about it. Also, don't assume because it says you're epe is 8 feet that this means you're accurate to 8 feet. It means the calculations that Garmin does should put you there a certain percentage of the time.

 

To see how you're really doing you can look at the geometry of the sats when you take your readings and that will give you a clue as to how accurate it really is. All overhead, all to one side or another give different results regardless of what the EPE says.

[+bittsen]

10ft if i remember right and i returned it and am trying to get best buy to price match it online at the moment. So no luck in trying it with the compass off. How would that affect it if you dont mind me asking.

 

Strictly from a logical point of view, and not having any data to back me up, the compass uses processing power. Turning it off will allow the unit to use the part of the processor that the compass is using. Thats just a hypothesis of why turning the compass off helps.

 

I did read somewhere when I was researching, prior to buying my own 400T, that the compass leads to a certain amount of inaccuracies to the positioning of the unit. If I recall correctly, it was attributed at +/- 30 feet of accuracy.

 

I agree with one of the comments above that stated the 400T tends to predict your movements and when you stop, it will settle back a few points. When I am placing a cache, I like to set the unit down for a couple minutes to let it settle. I do this 3 times to make sure the coords come back to the same ones each time. I didn't do this on the last cache I (re)placed because the mosquitos were thretening to remove more than their allotted share of my bodily fluids but I did get a great position reading after only 20 seconds or so, based on a check with Google maps.