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mathogre

Waypoint Averaging for Current Location and Dead Reckoning

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Hi!

 

I'm going after my second geocache.  My first was easy, and it was done with my iPhone.  Today I went out with both my iPhone and my new Garmin eTrex 30x.  (I last used GPS during Selective Availability.  I knew what I was getting into when getting a new GPSr.)

 

The cache is identified with Difficulty 2.  Once close, my position and thus the direction to the cache with both devices was sufficiently random as to wonder if clowns had taken over both my so-called smart phone and my GPSr.  Well, my GPSr has an ability to lay down a waypoint and average its location, albeit with accuracy if I wait 90 minutes with multiple readings.  I didn't have that amount of time today.  Still, I thought it would be a way to identify "my" location and navigate to the cache location accurately.  This assumes of course that the cache location is accurate.

 

Do people do that?  I would imagine there are some geocaches that are sufficiently challenging that it's worth the time and effort to get close to a cache, survey a known position, and do dead reckoning from there to the cache.

 

Fwiw, this cache is small with lots of interesting nearby locations to hide it.  It is also located in a bit of a valley, inviting the virtual navigational clowns to the party.  I've since returned to the web page for the cache to get some additional information, and I now think I know where to look.  I'll return tomorrow, a bit humbled.

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I have never averaged my location when looking for a cache.  I've only used that function when getting coords for my own hide.

 

Trying to zero-in on a cache location doesn't guarantee a find. After all, the hider and the finder would have to both get coords that are exactly right, so the general advice is to put away the GPS device one you get within a few feet and just start looking.

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1 hour ago, mathogre said:

The cache is identified with Difficulty 2.  Once close, my position and thus the direction to the cache with both devices was sufficiently random as to wonder if clowns had taken over both my so-called smart phone and my GPSr.  Well, my GPSr has an ability to lay down a waypoint and average its location, albeit with accuracy if I wait 90 minutes with multiple readings.  I didn't have that amount of time today.  Still, I thought it would be a way to identify "my" location and navigate to the cache location accurately.  This assumes of course that the cache location is accurate.

Do people do that?  I would imagine there are some geocaches that are sufficiently challenging that it's worth the time and effort to get close to a cache, survey a known position, and do dead reckoning from there to the cache.

Fwiw, this cache is small with lots of interesting nearby locations to hide it.  It is also located in a bit of a valley, inviting the virtual navigational clowns to the party.  I've since returned to the web page for the cache to get some additional information, and I now think I know where to look.  I'll return tomorrow, a bit humbled.

 

Like noncentric, we've only used waypoint averaging to place a cache (and go back different days too, if able).  

Accurate ?   

 - With civilian gps only "accurate" to around 10' on good days, we'd walk towards GZ and  put the gps away to start looking when close.   :)

I feel 2 difficulty is still "easy" enough that you may simply be overthinking things and with a few more finds,  you may feel the same. 

Good luck.

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4 hours ago, mathogre said:

Once close, my position and thus the direction to the cache with both devices was sufficiently random as to wonder if clowns had taken over both my so-called smart phone and my GPSr.

That sounds like the "drunken bee dance". As cerberus1 indicated, under ideal conditions, a consumer GPSr will be accurate to about 3m (10ft). So you could be standing right on top of the target coordinates and your device could show 10ft one way, then 7ft another way, then 5ft another way, then 9ft another way, and that's perfectly normal under ideal conditions. If you keep trying to follow the arrow once you get within this range, then you'll wander around like a drunken bee.

 

And of course, that accuracy limitation 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 the target coordinates, put your device away and look around for places where a container could be hidden.

 

I will sometimes set down my device (and maybe my backpack, bicycle, or other possessions) at ground zero while I search. That helps me remember where ground zero is, and if the search takes long enough, then its possible that the additional satellite readings can help it settle down a bit. But I don't count on that. Once I get within that range, it's a matter of searching for the hidden container.

 

Where would you hide something? Do you notice anything unusual? Is anything too new, too old, too organized (e.g., UPS: an Unnatural Pile of Sticks/Stones), too symmetrical, not quite the right color or shape, etc.? Don’t look only on the ground; the cache may be knee-level, waist-level, eye-level, or overhead. How might the container be secured in place? With magnets? With a hook? With string? With fishing line? With something else? Does anything move when you touch it? (Be careful when touching things though.)

 

Go ahead and read the cache's additional hints (if provided), and read the past logs and look at any photos in the cache's image gallery. They may help you understand what you're looking for, and how/where it may be hidden. It may also help to look at some of the cache containers available online. For example, check out the cache containers sold by Groundspeak. Also, take a look at the Pictures - Cool Cache Containers (CCC's) thread in the forums, and check out some geocaching videos on YouTube.
 

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The position readout of the GPSr seems to have more internal "buffering" than the compass pointer and will make corrections without you having to move, once I'm outside of the vehicle I switch the display page and navigate with only the position fields.

 

If GZ is at N30 40.400 W95 50.500 and your position is N30 40.350 W95 50.450 you know you need to head NW a fair distance. Once you get close to GZ the position will still slowly correct but it will be a matter of .001 minutes instead of 90 degree random compass swings, dead reckoning .001 minute is a snap. 

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Thank you, everyone!  I went back out this morning, and had a DNF.  What I did in advance was what you folks suggested.  I looked at hints, photos, and log entries.  When navigating, once I was near I went to the compass instead of the map.  I was in the right area yesterday, based on everything I learned.  I spent time looking for the cache in both immediate and surrounding areas.  While I'd already become familiar with the types of containers, I do need to familiarize myself with the greater range of containers.  Finally, I need to look at additional videos.

 

Ultimately I need to get a few more finds to get a sense of how people hide geocaches.  One remark in the log was that when the person looked from a different direction, it was obvious where it was located.  "Obvious" translates to experience.  I was all over the area and didn't have a sense of where it might be, though I looked, prodded, used a light, et al.

 

I'll come back to that geocache eventually.  I want to get more experience so that I know better how and where to look.

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18 minutes ago, mathogre said:

Ultimately I need to get a few more finds to get a sense of how people hide geocaches.  One remark in the log was that when the person looked from a different direction, it was obvious where it was located.  "Obvious" translates to experience.  I was all over the area and didn't have a sense of where it might be, though I looked, prodded, used a light, et al.

Yeah, unfortunately a lot of caches rated as low difficulty are rated that way because they're in "the usual spot". That doesn't really help newbies though, who haven't learned where "the usual spots" are yet.

 

But some of my earliest DNFs were that kind of inexperience. When I went back later to try again, I found them quickly.

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On 2/6/2019 at 3:06 AM, mathogre said:

Ultimately I need to get a few more finds to get a sense of how people hide geocaches.  One remark in the log was that when the person looked from a different direction, it was obvious where it was located.  "Obvious" translates to experience.  I was all over the area and didn't have a sense of where it might be, though I looked, prodded, used a light, et al.

 

I've been caching now for just on six years, with almost a thousand finds, but last week I went looking for a new multi, DNFing it the first time because I messed up one of the waypoints, then after correcting that, DNFing it again after searching for ages at the correct GZ. Yesterday that cache got two finds, saying they spotted it in a couple of minutes and it was shining like a beacon in the sunlight, so off I went again today, spending an hour searching, going off to grab lunch then back again for some more poking around. Nup, another DNF. Sometimes it just happens that way, what's obvious to one person is invisible to someone else.

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On ‎2‎/‎6‎/‎2019 at 8:53 PM, barefootjeff said:

I've been caching now for just on six years, with almost a thousand finds, but last week I went looking for a new multi, DNFing it the first time because I messed up one of the waypoints, then after correcting that, DNFing it again after searching for ages at the correct GZ. Yesterday that cache got two finds, saying they spotted it in a couple of minutes and it was shining like a beacon in the sunlight, so off I went again today, spending an hour searching, going off to grab lunch then back again for some more poking around. Nup, another DNF. Sometimes it just happens that way, what's obvious to one person is invisible to someone else.

In the same way that not having enough experience can make it tough to find caches, having too much can sometimes make it just as tough. Once you've seen lots of hide styles, it's easy to get hung up on looking for hides like the ones you've seen before, sometimes completely overlooking an obvious but new-to-you hiding style. There have been a number of times when I've read the description and hint, shown up to GZ figuring I knew exactly how it was hidden, and eventually realized I was wrong all along.

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2 hours ago, The A-Team said:

In the same way that not having enough experience can make it tough to find caches, having too much can sometimes make it just as tough. Once you've seen lots of hide styles, it's easy to get hung up on looking for hides like the ones you've seen before, sometimes completely overlooking an obvious but new-to-you hiding style. There have been a number of times when I've read the description and hint, shown up to GZ figuring I knew exactly how it was hidden, and eventually realized I was wrong all along.

Yep. I've found a couple caches that were really hard to find because there were multiple "obvious spots" for the cache to be hidden at GZ. After searching those "obvious spots" thoroughly, I eventually took a step back and found a cache that was hidden in some other way, a way that would have been very easy to notice if I hadn't been so focused on the "obvious spots" where it wasn't.

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12 hours ago, niraD said:

Yep. I've found a couple caches that were really hard to find because there were multiple "obvious spots" for the cache to be hidden at GZ. After searching those "obvious spots" thoroughly, I eventually took a step back and found a cache that was hidden in some other way, a way that would have been very easy to notice if I hadn't been so focused on the "obvious spots" where it wasn't.

 

A few years ago I was dropping my son off at the local YMCA and while waiting for him I noticed that from where I was standing I could see several lamp posts, a guard rail, a rock wall, several pine trees and a large green electrical box.  I thought it might be fun to hide a cache in a non-obvious spot given that there were so many hiding spots that others had used.  Then I remembered that I was basically standing in a parking lot and didn't want to hide a cache that would take finders to a parking lot.

 

One of my favorites was a cache where GZ seemed to be in the middle of a strip mall parking lot with several lamp posts.  The cache was actually in a culvert that ran under the parking lot (the entrance was about 200 feet from GZ).  There were a lot of DNFs and a few NM logs on that cache from some claiming that they searched the obvious spot and the cache was probably missing.

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