Help! Problem With Accurate Coordinates For New Cache

[+Seawind]

I created a new cache today, and tried to be very careful to get the coordinates as close as possible. With GPSr on, I first went to the planned site, then walked away from it a few times in various directions, followed by returning to the cache. I then let the GPSr sit right on the cache for over 10 minutes. I then saved the coordinates.

 

Later today, I returned with a friend to test the coordinates. We ended up at a point 80 feet away. So, we went right to the cache and let the GPSr sit for over 5 minutes. It continued to indicate the cache was 80 feet away.

 

I returned home and put the listing on hold (fortunately, it hadn't been published yet).

 

I've had similar problems in the past. What am I doing wrong?

 

My GPSr is a Magellan Meridian Gold. It seems quite accurate when I visit other caches.

 

The site of the new cache is on the western slope of a hill. There is a clear view of the sky in all directions except east. There is no tree cover.

 

How can I be sure I am posting accurate coordinates?

 

Thanks!

himilecyclist

Salt Lake City

[+Mudfrog]

You said that you let the GPSr sit on top of the cache for 10 minutes. Just having the unit on won't help much in getting good coordinates, at least i don't think so. With my Garmin, i "average" the location to get the best reading. This feature is accessed through the menu on my unit but im not sure how you do that with the Magellan. You would need to read the operating manual or better yet, get helpful advice from someone on here who is familar with your GPSr.

[+fizzymagic]

Just having the unit on won't help much in getting good coordinates, at least i don't think so.

Magellan units average automatically, so letting it sit for 10 minutes is a good idea for them.

 

I don't know what went wrong; perhaps your GPS had a bad solution during one of the visits. Go back tomorrow, and I am willing to bet it will give you readings very close to one of the two previous spots. Use that one.

[+Team Cotati]

I own a Gold. I have always had pretty good results by pacing towards the cache location from three different directions. Usually allow about 30 yds. distance between me and the cache location prior to beginning the approach. Average the results unless I get two sets that are equal, then I use those. Try it sometime and see what you think.

Edited March 3, 2006 by Team Cotati

[+Bear_Left]

A couple of tips:

 

The averaging function means that the GPSr takes a little while to 'catch up' when you stop at GZ, so it might help to turn the unit off and on again to make it forget the previous readings.

 

Once you've settled at GZ, mark a waypoint and then GOTO it. If you're suddenly several metres* away and it's consistent, then you should probably mark a new waypoint and repeat the process. This will give you an immediate idea of how much you're varying, and therefore how much confidence you should have in your reading.

 

Averaging can help eliminate 'glitch' readings, but at the end of the day, the GPS system has a finite accuracy and that's just part of the game!

 

*Yes, that's metric. Most of the rest of the world uses it.

[+Prime Suspect]

Some satellite constellations are better than others. If most of the birds you've locked on are grouped together overhead, rather than spread out closer to the horizon, it will impact your accuracy. There's a website somewhere (maybe someone knows the URL) that will show you the GPS satellite constellation for any given time and location.

[+whistler & co.]

We find that using brand new batteries increases the accuracy of the coords!!!

[+edscott]

Get a good on-line map and put your cursor over the spot

[+Huckleberry Slim]

Some satellite constellations are better than others. If most of the birds you've locked on are grouped together overhead, rather than spread out closer to the horizon, it will impact your accuracy. There's a website somewhere (maybe someone knows the URL) that will show you the GPS satellite constellation for any given time and location.

I got this answer in another thread when I asked about satellite traking websites.

[+Magoonies]

I also use a Magellan Meridian Gold. Put in fresh batteries like whistler said and make sure that the unit is over the cache like you would normally hold it. Don't set it on the cache with the screen up. The only time I have had a bad reading was when I set it on the metal cache. Hold it for about a minute, write down the coords and walk about fifty yards. Come back, from a different direction and repeat to get coordinates. I do that four or five times and have always had one set of coord come up at least three times. Good luck.

[+Glenn]

I place my GPSr in the place where I am going to put the cache. Check to make sure it is getting good reception. If not a move it a foot or two until it does. I leave the GPSr sit while I make last minute preps to the cache container. I then jold down GOTO on the GPSr and swap GPSr for cache and save the waypoint. Haven't had a compaint about the coordinates for my caches, yet.

[+geezer55]

What we've done is put GPS where the cache is hidden and turn it off and on about 10 times. We usually throw out 2 readings that are wayout. Add the numbers up behind the decimal point and average them out long-hand. It is time consuming but seems to work as people have found our caches without any hints. The only hints we give are to the trail head usually about .5 of a kilometer away from the cache.

[+Team GPSaxophone]

Walk in a circle around your cache, marking waypoints as you go. Take an average of the last 3 digits (one calculation for lat, one for long). Make a waypoint with these numbers, then check your map screen to make sure it's in the middle (roughly) of your circle.

 

The only complaints I've had about bad coords is when someone moved my cache!

[+Pablo Mac]

The only complaints I've had about bad coords is when someone moved my cache!

You don't get logs that mention how your coords were off, as if their GPSr couldn't possibly be off? I could use my sub-centimeter land survey GPS gear to place caches and still get those comments.

[+Team GPSaxophone]

The only complaints I've had about bad coords is when someone moved my cache!

You don't get logs that mention how your coords were off, as if their GPSr couldn't possibly be off? I could use my sub-centimeter land survey GPS gear to place caches and still get those comments.

I don't consider those logs to have any truth to them. Now, if they said the coords were off by more than 30 feet, I may wonder.

[+Pablo Mac]

I should probably try taking on that mindset instead of the immediate log deletion approach I've been taking...

[+TeamGuisinger]

Our Magellan gives crap readings if left setting still. We usually pace a giant * crossing at GZ, jot the readings down with each pass, and average. It always seems to get really good readings while moving, and the last time we set it down to watch it, it jumped 3 times @ 60-80' in 10 min.

[+Mudfrog]

Just read through this thread and boy howdy, you Magellan owners have a bunch of different techniques for obtaining proper readings. I have to say that i'm sure glad that i can just hold my Garmin over the cache and hit the average button to get good coordinates!

[+Airmapper]

Just read through this thread and boy howdy, you Magellan owners have a bunch of different techniques for obtaining proper readings. I have to say that i'm sure glad that i can just hold my Garmin over the cache and hit the average button to get good coordinates!

 

ROFL! Same here, only I use a Lowrance.

[+briansnat]

Just read through this thread and boy howdy, you Magellan owners have a bunch of different techniques for obtaining proper readings. I have to say that i'm sure glad that i can just hold my Garmin over the cache and hit the average button to get good coordinates!

 

You can get great coordinates using a Magellan as long as you use it properly. You have to let it settle for a few minutes before you even think of marking your waypoint.

 

That said, I can usually tell what unit the owner had by the accuracy of the coords. The Magellan waypoints are consistently farther off than those caches hidden by Garmin users. That's probably because the Magellan owners in my area don't let the unit "catch up" before marking their waypoint. Used properly however, Magellan units can provide coordinates as accurate as any Garmin. In fact they can even be a touch better if used correctly.