How close does a GPS get you

[TeamBawBags]

Just got a GPS unit and found a couple of caches. However it took a lot of finding as thet GPS never seemed to lock on to the exact (I mean exact) position. So how close should a GPS position get you?

 

So for instance if I program in

 

N 57° 28.698 W 004° 25.286

Or

British Grid: NH 54910 45694

 

does the GPS get me within say 20 yards/metres? Or is it close than that?

 

Or am I doing something wrong?

 

Thanks for any help ..... my son wants to go out again tonight !!

[+Gitchee-Gummee]

The earth is turning, you are walking, the satellites are flying...........

 

Think again about "locking on to the exact (I mean exact) position". What you want, or think you want, just is not gonna happen.

 

The GPSr is going to get you close, you may even kick the cache and not know it, but that is not what you should plan on. Six meters would be considered normal, even then it can vary greatly. Lots of variables (including user ability).

 

Geocaching is about the "hunt", it is not about using a GPSr to "deliver the package to me on a silver platter".

[+DonB]

Just got a GPS unit and found a couple of caches. However it took a lot of finding as thet GPS never seemed to lock on to the exact (I mean exact) position. So how close should a GPS position get you?

 

So for instance if I program in

 

N 57° 28.698 W 004° 25.286

Or

British Grid: NH 54910 45694

 

does the GPS get me within say 20 yards/metres? Or is it close than that?

 

Or am I doing something wrong?

 

Thanks for any help ..... my son wants to go out again tonight !!

From day to day there is no guaranty for accuracy. I have had the GPS take me to within two or three feet from the cache, but more often then not when I get close The GPS will start jumping around. When that happens, usually at about 20 or 30 feet, I will put the GPS away start using my eyes. The more you cache the better you will get at picking out the likely places it will be.

[+Kryten]

GPS receivers are accurate to about 30 feet (10 metres). The point at which the GPS indicates you have arrived is known as "ground zero" and once there The GPS has done it's job, it's just not going to take you to the exact spot and the fact that it doesn't is all part of the fun. As you approch ground zero start thinking "where would I hide it?". Does anything look out of place, a pile of sticks at the roots of a tree, look at the base of fence posts, is there any metal item to which something magnetic could be clinging, look around large rocks, in cracks in a wall, don't forget to look up and down too. The last 30 feet is a journey you take based on observation, experience and luck.

[+bootsycat]

The best tip I ever read was that once you get within 20 feet, PUT THE GPS IN YOUR POCKET AND USE YOUR EYES!! (Capitals are there to remind myself - constantly - that the cache is not going to appear on the screen of the GPS...) I watched my dad walking backwards and forwards the other day, watching the screen - while I poked about under trees. It seemed really obvious to me who was going to find it (and I did) - but I know I'm guilty of that most of the time. If it gets you to 5ft, great, but that doesn't necessarily mean you are exactly 5ft from the cache due to mathematical and sciencey reasons I'll let someone else explain. The GPS will get you close. Then it's your turn. Have fun!

[+Anti_Podean]

If you go to Google Maps and type "N 57° 28.698 W 004° 25.286 (test1)" into the search box and zoom in, you'll see it show a point near the end of Wardlaw Road. Try changing the last digit by 1 in both of the values (e.g. "N 57° 28.697 W 004° 25.285 (test2)") and see where the pointer displays when you zoom in. That's the maximum level of accuracy you can expect from the GPS of both the cache owner and yours.

 

This Wikipedia article gives more information that may help. In my vast geocaching experience (*ahem* 34 caches), I do what bootsycat does: once I'm close to the location I put it away and use my head and eyes.

 

tl;dr: As the coords cover an area larger than the 1x1ft patch you're standing on, the cache probably won't be under your feet when your GPS reads "0ft".

[TeamBawBags]

I was just trying to confirm what I thought ..... it gets me to the area and then I need to search. Not that it will get me to the exact point.

 

I was trying to ascertain at how near I can expect to get before I pocket the GPS. 25 feet is when it seems to start turning around and giving me strange readings.

 

Many thanks again.

[+bootsycat]

Tree cover etc will make it skippy too. I think *they* bug the GPS's to make them muck about at around 25ft... just to make us work harder!

[+Brooklyn51]

It can be helpful sometimes to walk away, maybe 30-40 feet, from where you think GZ (Ground Zero) is and come back to it from a different direction, especially if there is more than one likely hiding spot. And sometimes it helps to do this several times, a kind of triangulating if you will. This is otherwise know as the drunken bee dance. Most of us know some variation of it well. Then once you have a better idea where GZ is, again it's time to put the GPSr away and look around.

[+AustinMN]

Under ideal conditions at the equator, the coordinate system itself is only good to a square of about 12 feet x 12 feet (4 meters x 4 meters). That's if both your GPS and the cache owner's GPS read the location perfectly, something that never happens.

 

For one of my first caches (still a DNF, BTW), I wandered around for 20 minutes in heavy tree cover, and covered quite a bit of ground (including crossing my own tracks 4-5 times) trying to pinpoint GZ. Mighty frustrating for a micro.

 

Austin

[+StarBrand]

I was just trying to confirm what I thought ..... it gets me to the area and then I need to search. Not that it will get me to the exact point.

 

I was trying to ascertain at how near I can expect to get before I pocket the GPS. 25 feet is when it seems to start turning around and giving me strange readings.

 

Many thanks again.

The vast majority of the time under most satellite conditions and with a good receiver - you should be well within 20 feet. But up to 40 feet or so should be your expanded radius on rare occasion.

[jkettu]

I'm not sure if it is only an illusion, but I'm using the following technique and it seems to be more accurate than the drunken bee dance:

Walk along a line that intentionally passes the assumed GZ by 100-200 feet. Keep your speed as constant as possible. Note when the arrow is pointing directly to the side and note some landmarks to mark a line along which the true GZ is located. Continue walking well past the GZ on your original heading. Then turn 90°, again walk past the GZ and establish a second locator line to the true GZ. Now put away the gpsr, go to the intersection of those lines and start looking.

[+StarBrand]

I'm not sure if it is only an illusion, but I'm using the following technique and it seems to be more accurate than the drunken bee dance:

Walk along a line that intentionally passes the assumed GZ by 100-200 feet. Keep your speed as constant as possible. Note when the arrow is pointing directly to the side and note some landmarks to mark a line along which the true GZ is located. Continue walking well past the GZ on your original heading. Then turn 90°, again walk past the GZ and establish a second locator line to the true GZ. Now put away the gpsr, go to the intersection of those lines and start looking.

Not a bad technique - I have done that myself on occasion to pinpoint an area. Depending on vegitation, it isn't always fruitful but a good one to remember.

[+AustinMN]

I'm not sure if it is only an illusion, but I'm using the following technique and it seems to be more accurate than the drunken bee dance:

Walk along a line that intentionally passes the assumed GZ by 100-200 feet. Keep your speed as constant as possible. Note when the arrow is pointing directly to the side and note some landmarks to mark a line along which the true GZ is located. Continue walking well past the GZ on your original heading. Then turn 90°, again walk past the GZ and establish a second locator line to the true GZ. Now put away the gpsr, go to the intersection of those lines and start looking.

 

I sometimes do a variation on this. I walk a straight line until the cache is 90° off my direction of travel, then I turn directly towards it, walk a stright line towards it, and put the GPS away when I cross it again.

 

Austin

[+Markwell]

Hmmm... seems I documented something like that technique years ago - even included pictures.

 

http://markwell.us/geofaq.htm#Tri

[+breaultm]

I'd like to also point out that the coordinates posted are only as accurate as the GPSr of the person who put the Cache there in the first place. I've noticed this a few times that GZ on my GPSr would be dead-on on a Cache and off by as much as a 100 meters the very next Cache.

 

The "once you're around GZ, put your GPSr in your pocket" advice is much more powerful than it can seem when you're a beginner-Geocacher. When I started, I struggled with some easy caches because I had the reflex of relying too much on the GPSr.

Edited April 20, 2012 by breaultm

[+ByronForestPreserve]

Your GPSr should have a plus/minus feet(or meters) accuracy on a screen somewhere, too. I look at that mostly to gauge how far to expand my search area after I think I'm at GZ. Usually it reads +/- 6-8 feet, but when I turned it on today I saw +/- 65 feet!

[+BAMBOOZLE]

Using 62S, 60 CSx, Meridian Platinum I'll be within 10' as a rule by the time the log is signed.....maybe closer. The Oregon 450 not quite as close.