Correct Coords. For Placing A Cache

January 31, 2004

Before placing a cache, what is the best way to be sure you have the most accurate coords. for posting?

24.7k · January 31, 2004

Make sure you have a good lock when you save your waypoint.

Averaging helps but not nearly as much as making sure you have a good signal.

1.4k · January 31, 2004

There are a lot of different opinions on how to do this.

I personally take multiple waypoints on different days. 6-10 waypoints a day over two or three days. Each time I take a waypoint I’ll walk away from the cache anywhere from 100-200 feet in different directions. Then when I return I’ll let my GPS sit for a few minutes to get settled. I then drop the highest and lowest set of coords and average the rest.

I’ve never had any complaints using this method.

9.2k · January 31, 2004

Before placing a cache, what is the best way to be sure you have the most accurate coords. for posting?

Just make sure you've got a good lock on as many satellites as you can. Don't bother averaging - it's pointless. It made a little sense back when SA was turned on, due to the randomness of the signal. But the errors you'll encounter now aren't random (in the mathematical sense), and averaging them together isn't going to give you better data.

If you can move 10 feet away from your cache and get a much better signal - do it. Those coordinates will be more useful than coordinates derived from poor signals taken right next to the cache.

January 31, 2004

I average my coords when placing a cache all the time.

It lets me enjoy the spot and my gps does it so I use it. I find it makes no differance though.

:rolleyes:

January 31, 2004

The reason for this question is that I just placed a cache and had it approved but the map shows it in the water. The accuracy when I placed the cache was 10 feet if I remember correctly but it was placed a good 30'-35' from the water. Is this normal or should I go and move it?

5.3k · January 31, 2004

The reason for this question is that I just placed a cache and had it approved but the map shows it in the water. The accuracy when I placed the cache was 10 feet if I remember correctly but it was placed a good 30'-35' from the water. Is this normal or should I go and move it?

Maps are not perfect. If you are afraid your coords are bad, go take another reading and see if they are off.

38.2k · January 31, 2004

I averaged in the beginning....by marking a waypoint, then moving away from the cache, then back and marking another. I'd do this about 20 or so times. Now I just make sure I have a good lock and take one. I've found no difference in accuracy and in fact the one cache that I get the most compaints about the coordinates was one that I averaged.

I think it's really just a waste of time. Mark one waypoint and use it. If you get complaints, go back again and take another...but I bet you probably won't have to.

I also agree with Prime Suspect...a good reading 10 -20 feet away from the cache is better than a bad one right on it....so if you can get a better lock by moving a bit away, do it.

Edited January 31, 2004 by briansnat

January 31, 2004

ok thanks for the help, since I am working 12 shifts this weekend I will have to check it tues. Maybe someone will find it before then and confirm that it's alright.

:rolleyes: mark

January 31, 2004

It's due to error's on the Mapquest maps. I checked your coordinates on a USGS topo map as well as an aerial image from Terraserver and they both show your coordinates just to the west of the river. Waypoint averaging certainly still does make a significant improvement in accuracy if your willing to do it for 30 minutes or so although even as little as 10-20 minutes will also make an improvement. See this page on detailed tests on averaging. Here's a pic of your location on the aerial photo.

Edited January 31, 2004 by Poindexter

1.7k · January 31, 2004

I shut down my GPS and then power it up while it is sitting on where I will place my cache. This clears out any averaging or slingshot effect from my travling to the cache site.

Then I let it set there for 10 minutes or so while I hide my cache and relax, and then I mark my point. (Assuming I had a good satellite lock.)

4.1k · February 1, 2004

All of the above answers are good, but they left out the most important one. Be sure to use a Magellan Meridan Platinum!! :mad:

Just have a good lock and wait a little while for the GPSr to settle in.

John

February 5, 2004

I've found averaging over multiple days makes a HUGE difference.

I usually make sure it has good signal (lotsa' birds close to the horizon rather than directly overhead) and mark a waypoint when I find my hidey-hole.

The next day I come back, verify good signal and mark a second, prep/place the container and camo (15 mins. or so). I then mark another waypoint.

Average the three together and there you go. Never a complaint, many compliments and I have several tricky multis, night caches and puzzles with rather involved setups.

I know one local cacher who got a lot of complaints until adopting averaging. Sure, most the time it'll work without, but every now and then the odds work against you.

Enjoy,

Randy

PS: Experienced cachers won't notice if the coords are off as they'll stop looking at their GPS when approaching within 20-40' and start hunting instead. (Somehow I don't like that grammar but can't decide if it's truely bad--oh well, after midnight, what do you want?)

February 5, 2004

My question is, if you don't have a gps which averages, how do you average waypoints?

February 5, 2004

Out of my six hidden caches so far, I've only had trouble with one. My GPS would just not settle down and decide on any sort of consistent reading. I took probably eight readings approaching from different directions. There was a varience of about 110' from one extreme of the readings to the other. Finally, I just gave up and threw out the extreme ones and averaged the ones sort of in the middle.

I just put right on the cache page what had happened, and asked that the first few finders email me to see what they got for coordinates. Since I am pretty much the only one hiding caches in my immediate area right now, I tend to get a few emails anyway which say things like, "I saw you hid a new one today. I'm going to go out and look for it as soon as I get a chance." I got two responses, and my coordinates were evidently about 30' off. Both of these gentlemen were kind enough to get several readings each, and their readings were consistent with each other, and they were taken on different days. I went ahead and adjusted my coordinates a little bit on the strength of this evidence.

In the days since then, we've gotten quite a blanket of snow with more forecast, so I doubt anybody's going to find it for a while, since it's a near-micro with a white colored lid, and it's on the ground. So verifying this further will probably have to wait. Anyhow, that's how I resolved the problem.

Oh, yeah, I guess the important thing is that even with the coordinates being off, two people managed to find the little 1/2 cup Rubbermaid container in the woods right away. One more found it after the coordinates were adjusted, and snow foiled a fourth. I think as long as you're in the realm, say 25 feet, somebody will find it.

38.2k · February 5, 2004

I know one local cacher who got a lot of complaints until adopting averaging. Sure, most the time it'll work without, but every now and then the odds work against you.

I've placed 60+ caches. I averaged probably the first 10 I placed and haven't since. I've received complaints about the coordinates for two of my caches. One was averaged and the other wasn't. In fact the logs will sometimes say something like, "your coords were dead on as usual". Probably because I use a Garmin .

So I save myself a lot of time and just take one reading and go with it.

Edited February 5, 2004 by briansnat

9.4k · February 5, 2004

I walk around the cache taking waypoints at each quadrant of my circle. I average those 4 readings together. I also go back within the first week after placing it to make sure my GPS leads me right to it. I haven't had any complaints of being off by any more than my GPSr's accuracy reading.

1.8k · February 5, 2004

I don't go too crazy trying to get super-accurate coordinates. Usually I won't have the container with me when I'm looking for a decent hiding spot. When I find one I mark the waypoint.

When I return with the cache, if the waypoint gets me to the cache site within 10-15 feet or so, I consider that to be reasonable.

Even if I get the coordinates just perfect, the next cacher could come at a time when there are only eight satellites in view and might be way off anyway.

So I don't fret it too much.

February 5, 2004

It's due to error's on the Mapquest maps. I checked your coordinates on a USGS topo map as well as an aerial image from Terraserver and they both show your coordinates just to the west of the river. Waypoint averaging certainly still does make a significant improvement in accuracy if your willing to do it for 30 minutes or so although even as little as 10-20 minutes will also make an improvement. See this page on detailed tests on averaging. Here's a pic of your location on the aerial photo.

The discussion on averaging you point to is good stuff, however it is more discussing averaging as a function of time, as opposed to, taking one reading then walk around and come back to take another....most people don't have 12 hours to wait to get meaningful "averages"...wish I did...it would be nice to hang around some of the caches that long!

February 5, 2004

The discussion on averaging you point to is good stuff, however it is more discussing averaging as a function of time, as opposed to, taking one reading then walk around and come back to take another....most people don't have 12 hours to wait to get meaningful "averages"...wish I did...it would be nice to hang around some of the caches that long!

For those of us who have receivers that do waypoint averaging, it only takes about 15-20 minutes of averaging to significantly improve the accuracy of the fix. Accuracy is dependent on the geometry of the satellites being used to get a fix and the satellites are in motion so that's why averaging improves accuracy. It is much better to average with fixes being taken every second than just walking away and coming back to get another fix. Sure, the longer you average the better, but the biggest increase in accuracy occurs within the first hour.

February 5, 2004

If your unit doesn't average and you have taken 6 or 8 readings, how do you average them mathematically? Using pencil and paper, how is it done.

February 5, 2004

If your unit doesn't average and you have taken 6 or 8 readings, how do you average them mathematically? Using pencil and paper, how is it done.

That's what I do. I average the latitude and longitudes numbers separately. Usually the numbers are grouped fairly close together, and it's obvious what to do. Sometimes you'll get a reading which is quite a ways off of the others, and then you have to decide whether to throw that out and not make it a part of your "averaging."

On edit: Just to make sure I'm not being vague here, let me give an example. Let's suppose you took five readings, and they were:

N40° 00.100', W090° 00.200'

N40° 00.098', W090° 00.205'

N40° 00.098', W090° 00.203'

N40° 00.095', W090° 00.197'

N40° 00.099', W090° 00.198'

I would take the average of the latitude readings, which is N40° 00.098, then the average of the longitude readings, which is, rounded off, W090° 00201. That is what I would post as my coodinates. Just as a test, program the averaged coordinates into your GPSr and see if they lead you properly to the cache you hid the day before or whenever. If they do, then you can sleep peacefully at night.

The tricky bit comes if you get a reading on the above example like N40° 00.100, W090° 00.220. Do you throw the .220 out? I would say yes. There is no substitute for going back later and checking your averaged coodinates at a later date, however.

Edited February 5, 2004 by Balboagirl

1.1k · February 5, 2004

Averaging? (and especially auto-averaging) is really a feel good thing, if it feels good then do it but the chance of any improvement is 50/50, which means one can actually achieve coordinates that can be worse. Averaging isn't simply a one way factor and averaging certainly doesn't necessarily make a position better.

The first factor in "knowing" that the cooridnates are the best possible on the day is to do the positioning at the best time(s) of the day.

Cheers, Kerry.

Edited February 5, 2004 by Kerry.

February 5, 2004

In a park that has many caches,how do you know if yours is far enough away? Would 33 02. 901 096 51. 264 get booted because one is at 33 02. 863 096 50. 902 ?

8.9k · February 5, 2004

You can always use this resource. Plugging in the numbers (go ahead and plug the numbers with decimals into the minutes, just use 0 for seconds) gets you that these caches are 0.352 miles apart. 0.35>0.10=Cache location should be OK.

8.9k · February 5, 2004

Continued...

You can also plug your coordinates into the Advanced Seek page and the distances to other caches will be shown.

If I were placing a cache in an area with a high cache density, I'd be sure to plug all the caches for 5 miles around into my GPS. Then when I find a good spot, I'd check the distance to the other waypoints with my GOTO feature just to be sure.

BTW - I'd also probably try to find all the caches in that area before placing another one there.

February 5, 2004

probably time to set the ancient garmin free and get one I can plug coords into. gonna be hard! we have 70 finds together

February 6, 2004

This may be slightly off topic but close enough . Accuracy of waypoints is very much dependent on the geometry of the satellites. Averaging may help due to time and the location of the satelites, but if the satellites are poorly arranged, you will not get a consistent reading. Time is more important than days. I couldn't figure out how to post a picture of the software at work, but follow the link to get it. It'll graphically show you when the satellites are best aligned during the day for best accuracy (DOP). If your PDOP is low , then you won't need to average to get an accurate reading. The software has no cost and is from Trimble.

Trimble Planning Software

Goldhound9

February 6, 2004

Good point Goldhound9. I was going to post that link this morning but you beat me to it. If you use this software, you'll see that there are brief periods of times of the day when the DOP spikes very high and accuracy will be way off. I just did a Garmin 152 installation on a boat yesterday and for the first time for me, I saw 12 satellites at once, one being WAAS, with corrections being applied to all 11 satellites. DOP was .7 and the indicated accuracy was 7.1'. That's the best Iv'e seen here at 39° latitude.

February 6, 2004

I personally don't like just averaging. I use a meridian green, and usually let my coords average for 1-5 minutes, but thats not all. Each time that I return to the cache, I take another 1-5 minute average. I then take all the waypoints that I have collected, and graph them. It's usually easy to see groupings, and I delete the ones that are fairly far outside of the main grouping under the assumption that they aren't as good. I will then take all the coords in the grouping, and average them. I use that average as my final coordinates. I constantly update the coords on my cache pages whenever I make a return visit to one of my caches.

February 7, 2004

OK,

Finally figured out how to do what I wanted in the previous post (post a pix). The Trimble software can show a graph of when your GPSr will be the most accurate. The lower the number, the more accurate your reading will be :rolleyes: . The software also plots where the satellites will be at whatever time you choose. Well worth checking out and the price is right. 8am and 2:00pm are good times to acquire your coordinates.

Edit: times

Edited February 7, 2004 by Goldhound9

February 7, 2004

Its a miracle I ever got one! I didnt know these things, I go out between

9am and noon because of traffic here! :rolleyes:

Correct Coords. For Placing A Cache

Recommended Posts

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Link to comment

Join the conversation