Coords & distance

[+jpbanksnj]

I'm new to Geocaching and have noticed that all of my finds are within a certain small distance of the GZ location, but never exactly at that GZ point. What are the distance limits that a Cache can be from GZ?

[+wmpastor]

I'm new to Geocaching and have noticed that all of my finds are within a certain small distance of the GZ location, but never exactly at that GZ point. What are the distance limits that a Cache can be from GZ?

The hide is supposed to be exactly at the listed GZ coordinates. However, when coords are measured, there may be slight errors. Also, the hider and searcher have two different GPSr units, each with a slight possibile error. So figure a potential of maybe 25 feet of error, hopefully much less. If it's a lot more, someone did something wrong.

[+Isonzo Karst]

If you're finding the cache off the coords as much as 45 or even 60ft (60ft in an environment that badly degrades the signal, like urban building canyons, natural canyons, heavy tree cover) you are seeing the position uncertainty that is inherent to user grade gps units.

 

To reliably find something exactly on the coordinates, those coordinates need to be supplied by someone using surveyor quality gps equipment and you need to be using surveyor quality equipment to search for it.

 

edit speeling

Edited December 24, 2016 by Isonzo Karst

[+Touchstone]

A useful article in the Help Center goes into further detail regarding GPS accuracy and how to improve the reliability of your coordinates:

 

How to get accurate coordinates.

[+BCandMsKitty]

If you're asking with regard to searching, then if you get on average, to within 20 or 25 feet of a cache, you're doing good. That's when you put the GPSr down and look.

As for hiding, you need to get the best coords you can, which will reduce the distance differences with other cacher's units.

Follow the advice on the already listed links. Once you have your coords, a good practice that I di, is to check the coords by walking away and follow your coord back to see how close you get. This will tell you if you shot good coords or not.... at least for your unit.

[+niraD]

Under ideal conditions, a consumer GPSr will be accurate to about 3m (10ft). That applies both to your device, and to the cache owner’s device, so you may find the container 5-6m (16-20ft) from ground zero under ideal conditions. Under less than ideal conditions, both GPSr readings can be much less accurate. Once you get within that distance of ground zero, put your device away and look around for places where a container could be hidden.

[+ecanderson]

In the FWIW category:

 

I see GZ (ground zero) frequently here and in log postings. At least to my mind, it is often misused:

 

GZ = actual position of cache

Posted Coordinates = whatever the cache page says.

 

A cache is never xx feet from GZ. It's position IS GZ.

 

A cache is xx feet from 'posted' or 'posted coordinates', but lives at GZ.

 

The reason that I bring this up is that cache logs are often confusing because of this. When someone says " 30 feet east of GZ ", do they mean that the posted coordinates are 30' east of physical cache location? Probably not. They probably mean that GZ is 30' east of posted coordinates, and hence, that the posted coordinates are 30' W of GZ.

 

Not usually a big deal, but when the coordinates are particularly bad, it's helpful to know for certain which way the offset runs when reading the logs.

[+TeamRabbitRun]

In the FWIW category:

 

I see GZ (ground zero) frequently here and in log postings. At least to my mind, it is often misused:

 

GZ = actual position of cache

Posted Coordinates = whatever the cache page says.

 

A cache is never xx feet from GZ. It's position IS GZ.

 

A cache is xx feet from 'posted' or 'posted coordinates', but lives at GZ.

 

The reason that I bring this up is that cache logs are often confusing because of this. When someone says " 30 feet east of GZ ", do they mean that the posted coordinates are 30' east of physical cache location? Probably not. They probably mean that GZ is 30' east of posted coordinates, and hence, that the posted coordinates are 30' W of GZ.

 

Not usually a big deal, but when the coordinates are particularly bad, it's helpful to know for certain which way the offset runs when reading the logs.

 

At first glance, this seems like ridiculous nitpicking, but it's NOT! This important little writeup should be featured as a part of the HELP article on 'Hiding and Hunting' or whatever it is.

[Spurges]

In my mind, GZ has always meant the posted (or corrected) coordinates. Basically, my stated destination.

 

The Geocaching Glossary of Terms seems to agree with me (maybe that's where I got it):

 

Ground Zero (GZ)

The point where your GPS device shows that you have reached the geocache location. At ground zero, you are zero feet (or zero meters) away from your destination.

[+niraD]

From the Geocaching Glossary of Terms:

Ground Zero (GZ)

The point where your GPS device shows that you have reached the geocache location. At ground zero, you are zero feet (or zero meters) away from your destination.

That's how I've always used the term GZ or ground zero. It's where my device (or other navigation) says the location is. It's where my search starts. It is (usually) only approximately where the cache is located.

 

If I say that I found the cache "30 feet east of GZ", then I'm saying I had to expand my search 30 feet to the east of where I started searching for the cache. (I'm also saying that I'm being pretty nit-picky, because an error of up to 30 feet isn't really unexpected.)

[+ecanderson]

Then somebody had better come up with another term (other than GZ) when referencing the actual cache location. As it stands now, logs can be VERY confusing due to inconsistent use of terminology.

 

I had never seen that "Ground Zero (GZ)" reference before. Where can one find it?

 

In usage in any other context than geocaching, 'Ground Zero' is the location where something actually is or happens, irrespective of any intent to have it anywhere else (e.g., posted coordinates).

You can aim a rocket at any set of coordinates you like. Where it actually hits is "Ground Zero".

[+ecanderson]

If I say that I found the cache "30 feet east of GZ", then ...

Then you've qualified your use of it enough by differentiating the cache location and what you mean by "GZ" so that it was clear what you meant.

Unfortunately, not all logs are that specific.

 

"Bad coordinates. We were 80' east of GZ".

 

Now what do you suppose THAT means? I've seen it used to mean the cache was 80' E of posted, and also used to mean that the posted coordinates are 80' E of the cache.

There are two very different ways to interpret that sentence, one of which will make the search even worse for you than for the person making the post!

Edited December 28, 2016 by ecanderson

[+niraD]

Then somebody had better come up with another term (other than GZ) when referencing the actual cache location.

How about "cache location"?

 

I had never seen that "Ground Zero (GZ)" reference before. Where can one find it?

The "Glossary of Terms" links in the previous posts should do it.

 

In usage in any other context than geocaching, 'Ground Zero' is the location where something actually is or happens, irrespective of any intent to have it anywhere else (e.g., posted coordinates).

You can aim a rocket at any set of coordinates you like. Where it actually hits is "Ground Zero".

As a geocache seeker, I am not launching the geocache. I am launching a search. My search will land where the device points, and then I will expand my search radius (blast radius) from there. At least, that's how I think of it.

 

And sometimes, after expanding my search radius 30 feet or more, I'll return to GZ and find the cache sitting next to (or even under) my backpack, or bicycle, or whatever else I left at GZ to indicate where my search had started. But I digress...

[+TeamRabbitRun]

We're trying to shoehorn multiple objects into the same metaphorical usage.

 

"Ground-Zero" is a term originally meant to designate the actual pinpoint location of SOMETHING: a bombblast, a range target, a spaceship touchdown, a planned landing site, an earthquake epicenter, etc.

 

So, in OUR context, this thread is pulling back and forth over which of the two equally-eligible locations get possession of the term, when in actuality we could say "The search's Ground Zero proved to be 100 feet west of the hide's Ground Zero."

 

So, Darin's right, ecanderson's right, and I'm right.

 

<opinion> I think the use of the term in the GS Glossary is a sloppy one because of the multiple possible reference points. </opinion> Unless they think that way, most people wouldn't put a lot of analysis into writing that when they're making an easy point.

 

So, let's agree that there's confusion, and strive to be more clear in our logs, rather than relying on everyone knowing WHICH definition is the RIGHT one.

"The search put me right at Ground Zero."

 

"Once I found the cache, I saw that the posted coordinates were located twenty feet from the actual Ground Zero."

 

"Without tree cover, my GPSr easily took me directly to Ground Zero, and I found the cache thirty feet away."

[+The A-Team]

...getting back on topic...

 

What are the distance limits that a Cache can be from GZ?

There isn't a set limit. The ideal answer is "zero", but the reality with consumer GPS devices is that this will rarely occur.

 

When you're hiding a cache, you're supposed to do your best to get the most accurate coordinates you can, with the understanding that the inherent limitations of both the hider's and seeker's devices will introduce some inaccuracy. If a hider intentionally uses bad coordinates (often in a misguided attempt to make the cache more difficult), they're generally referred to by the derogatory term "soft coordinates" and are strongly discouraged. Caches with soft coordinates can lead to seekers damaging an area in their attempts to find the cache in the wrong spot, and I've seen caches get archived when a reviewer learned that the hider had intentionally used inaccurate coordinates, because the cache would violate the guidelines:

II-1.-1.: Listings must contain accurate GPS coordinates.

[+ecanderson]

Fair enough. As long as finders are sufficiently explicit in their logs, it's not a problem. Trouble is, they're not always so explicit.

As I say, this is the only paradigm wherein 'ground zero' is the ideal target location instead of the actual location for something to exist or to have occurred. At a minimum, it's a very odd use for the expression.

[+edscott]

I usually log it in a less confusing way as in "My GPS says it is 35 feet SW of the posted coordinates".

[+ecanderson]

Super helpful style, Ed. I need to follow you around in PA!

[+J Grouchy]

I usually log it in a less confusing way as in "My GPS says it is 35 feet SW of the posted coordinates".

 

If I were to be honest, I'd have to write "My GPS says it is 35 feet...no, 20 feet...no, 13 feet...no, 48 feet SW of...no, 37 feet NE of...no, 8 feet NW of the posted coordinates. Oh wait...now it says I'm 240 feet off..."