GPS always takes me past a cache...why?

[+res2100]

Seems like so many time when I am going caching, I follow my GPS and almost every time it takes me about 10-20 meters past a cache, only to then tell me that i have to turn around. Am I just walking too fast for my GPS to keep up? I have a SporTrak Pro.

 

http://ca.geocities.com/rsab2100/pond.html

[GRANDMASTER CACHE]

Hi,

 

I think we all have to get our own "method" we feel comfortable with. I generally have the "direction" of the cache which comes from "closing in" on it while walking that last 500ft. When it gets to -50ft, I start to slow down a bit. I like to walk real slow until the unit shows the cache as either my "9:00 position" or my "3:00 position." Basicaly, when it's perpendicular to the direction I'm walking. I'll keep walking past it, to verify that I'm "passing" the cache. I might turn around and walk back once or twice to see if there's consistancy to the reading. By this time, one of my crumb-snatchers is already squealing "I found it!!" Some times, it takes some "zeroing in," but to do this I like to use that "perpendicular" search method. If I get it on one axis, I'll walk along that axis until I get another "perpendicular" reading... I hope that doesn't sound confusing. It's basically just establishing two axis, and honing in on where they appear to intersect.

 

Now keep in mind, there can be a pretty significant "variance" because you are going off of someone else's coordinates, ya know? If you feel your consistantly "off" however, you might try to slow down and "hone in" on it with the method I've described. That's what really works for me. It's basically just a two-axis method of averaging. HTH!

 

Grandmaster Cache

[+Jamie Z]

Res... I use a Magellan Meridian Gold, and I experience the same sort of phenomenon. At a recent geocaching get-together in town, I brought this up, and other Magellan owners told me that they'd had the same problem.

 

It seems to me that this is a Magellan-related issue.

 

Um... get used to it is the only advice I can offer.

 

Well, not the only advice, but probably the best. One way I get around the problem is that I'll walk until my Meridian says I'm real close, then I'll turn off the unit, and then turn it back on; let it reacquire satellite lock. I've found that almost every time, the "new" readings it gives me are much closer to the actual cache location.

 

Another method is to walk until the GPS says you are close, then just wait a few minutes and let it average. You'll see the distance to the cache get smaller and smaller (or bigger and bigger, depending on where you are in relation).

 

Jamie

[+infosponge]

Magellan GPSR's seem to use a speed-averaging algorithm to factor in to the position calculation. This seems to work great when you're in a vehicle, but creates a "slingshot" effect when walking towards a cache while geocaching.

When I get below 100 feet, I usually stop walking for about 30 seconds to let the unit settle out.

[Kerry.]

Being a Magellan it could be (most likely) related to auto averaging. At a slow pace and with auto averaging kicked in (even though you are still moving) the averaged position will be behind you, then when you do stop (full stop proper) it will gradually catch up to where you really are and be telling you to go back.

 

Auto averaging silly silly idea.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+jollybgood]

I recently did a 12 cache hunting spree with two fellow geocachers. I found virutally EVERY cache first. By the end of the day they were pretty depressed and were wondering why my GPSr worked better than theirs.

 

My secret? When I start getting within a hundred feet of the cache I stop looking at my GPSr so much and start scanning the area ahead of me. I hold my GPSr up high at eye level so and merely glance at it now and then to check my progress/proximity of the cache while I look for the obvious hiding spots and ask myself, "Where would I try to hide it?"

 

I find that 70% of the time this works. The other 30% of the time it eliminates the obvious spots so I can concentrate on the less obvious places.

 

20 to 30 feet accuracy may sound like the GPSr should put you RIGHT on the cache but when you factor in the accuracy the Hider's unit with your own you could be up to 80 or 100 feet apart quite easily. I find scanning the area ahead and saves a lot of back tracking.

 

Jolly R. Blackburn

http://kenzerco.com

[+Sissy-n-CR]

All good advise. I own a SporTrak Map and I do the slow down to a crawl about 100'-75' out. I, too, scan the area for likely spots, but I also have Sissy with me. I call out distance and she takes clues from how I'm walking to know how to search.

 

With these units, you simply can't walk right to the spot and expect BANG! be right on. When settled this units are very accruate and I doubt many experienced Magellan users would would trade. I wouldn't. (Well, unless it's for a Pro model. )

 

CR

 

[+Mopar]

Sounds like you new Sport Trak owners may have to resurect the ancient Maggy ritual, known as the Hula Wave.

 

Tae-Kwon-Leap is not a path to a door, but a road leading forever towards the horizon.

[+azmark]

the old maggies had the to slow averaging problem, that you had to hula wave, but they also had a big problem with the speed averaging, that even at a run would let you over run a cache by 200ft.

 

the 3.15v upgrade for the Magellan 315 seemed to be a great one for geocachers, seems a bit of this has crept back into the newer units unfortunatly. what can be a feature for people in boats and cars can be a bug for cachers. maybe magellan could come out with a cacher patch.

[solohiker]

I have a very simple and reliable technique for locating a cache. After I have the cache waypoint in my gps I switch map format to UTM and my map datum to NAD27.

 

Now I have a location marked in linear meters instead of angular degrees. When I get near the cache I compare my current location with the location of the cache. By subtracting the Northing and Easting I can determine how many meters N/S and E/W I need to go.

 

I orient myself to the North or South and walk off the calculated distance and then go East or West to get to the cache.

 

Chasing the arrow is a waste of time.

[+Genius Loci]

I have one and I concur. For caching, I usually use some combination of the techniques mentioned above, especially the 'Hula' and Jolly's method of starting to look for logical cache hiding spots before the distance zeros out.

[+sbukosky]

On Garmins, if the road lock feature is on, it will give you some trouble close in. I don't know about other brands.

 

Steve Bukosky N9BGH

Waukesha Wisconsin

[+Trudy & the beast]

Slow down. The birds cycle through their signals every thiry seconds. At a good clip, you can easily cover 10-20 yards in that time. It's been said above, in a couple of different ways, when you start to get close to the cache you will need to slow down and change your technique. Give the birds the opportunity to take you to the cache. When you hit 50-100 feet, put your brakes on.

 

Keep on caching.

tb

[+Chichikov]

quote:

---

Originally posted by Jolly B Good:

... My secret? When I start getting within a hundred feet of the cache I stop looking at my GPSr so much and start scanning the area ahead of me. I hold my GPSr up high at eye level so and merely glance at it now and then to check my progress/proximity of the cache while I look for the obvious hiding spots and ask myself, "Where would I try to hide it?"...Jolly R. Blackburn

http://kenzerco.com

 

This is what I do also. My inspiration comes from Wayne Gretsky, who, when asked the secret of his success at hockey, said "I just skate where I think the puck is going to be."

[+Jamie Z]

quote:

---

Originally posted by Chichikov:

Wayne Gretsky, who, when asked the secret of his success at hockey, said "I just skate where I think the puck is going to be."

---

He also said once, when asked about an impossible goal he made between the goalie and the post, "There was room, I just had to turn the puck on its side."

 

Jamie

[+Mopar]

quote:

---

Originally posted by Trudy & The Beast:

Slow down. The birds cycle through their signals every thiry seconds. At a good clip, you can easily cover 10-20 yards in that time. It's been said above, in a couple of different ways, when you start to get close to the cache you will need to slow down and change your technique. Give the birds the opportunity to take you to the cache. When you hit 50-100 feet, put your brakes on.

 

Keep on caching.

tb

---

Actually, if its a variation of the old maggie auto averaging problem, the reverse is true. When you slowed down too much, they automagially went into averaging mode. Since you wernt actually stopped, your display would keep displaying an avg of you previous positions. When you finally stand still, the avgs finally catch up to you, by which time your probably already past the cache. Doing the "Hula Wave" speeds up the GPS, breaking it out of averaging mode.

I don't know for sure this is the problem the newwer maggies are having yet, as I don't own a sportrak but I know someone who's planing on getting one, so I guess I'll get to try it out for myself.

 

Tae-Kwon-Leap is not a path to a door, but a road leading forever towards the horizon.

[+Jamie Z]

quote:

---

Originally posted by Mopar:

if its a variation of the old maggie auto averaging problem,

---

Mopar, I don't think this is the case--at least with my Meridian. You can clearly see when the GPS goes into autoaveraging mode, and the described phenomenon happens even when autoaveraging never comes on.

 

The current Magellans come out of averaging with little more than passing the unit from hand to hand. Even walking at an extremely slow pace is enough to keep it from autoaveraging.

 

Infosponge's statement that:

quote:

---

Magellan GPSR's seem to use a speed-averaging algorithm to factor in to the position calculation.

---

seems the most likely cause to me.

 

Jamie

[+headmj]

All the Meridians come out of auto averaging so easily that I have NEVER had autoaveraging cause me a problem. No Hulas are required. My problem is keeping them in averaging mode when changing hands.

 

That said, there does seem to be an algorithim in the receiver that takes into account the speed you are walking and does location projections. I set the alarm for 100 feet. When it goes off I stop and wait about 30 seconds for the device to catch up. I can then usually proceed directly and slowly to the cache site.

[+geospotter]

I did my first cache with my new Meridian today. At first I wasn't sure I was at the right spot since the GPS said it was 192 ft. farther up the road. I was sure from the cache description that I was at the right spot so I waited and watched the GPS. Eventually (about 3 minutes) the distance dropped to 37 ft.

 

Now, this is unusual to me since my Mag315 never acted that way. The 315 always seemed to react quickly. If I walked by the cache the arrow let me know it immediately, making the hunt pretty easy.

 

I'll try a few more hunts with the Meridian, but I'll keep the 315 handy for comparison.

 

(For reference: I turned on the Meridian about 15 ft. from the cache while sitting parked in my car, so I don't think speed averaging was involved.)

 

geospotter

 

UPDATE: I used my Meridian for a 5-part multi today and it performed flawlessly. Very responsive. No complaints.

 

[This message was edited by geospotter on December 23, 2002 at 09:10 AM.]

[+writer]

quote:

---

Originally posted by solohiker:

I have a very simple and reliable technique for locating a cache. After I have the cache waypoint in my gps I switch map format to UTM and my map datum to NAD27.

---

 

Going with linear meters makes sense to me, but why make the switch after you enter the waypoint? The cache pages offer UTM already just under the lon/lat (though as far as I know they don't download to EasyGPS). Also, if you aren't working off a map, too, then NAD27 doesn't buy you anything, and actually might be a bit less accurate. To my mind, the fewer conversions, the less chance for additional error. But maybe I'm missing something, in which case I'd appreciate it if you could explain...

[+Slower Pace]

I haven't found as many caches as some of the pros here on the forum, but I usually connect. What I do with my Magellan 315 is use the compass screen till I get to within 100 feet. My alarm beeps. I stop for a few seconds, turn off the alarm, and go to my position screen. I walk to line up one of the coordinates. I usually go past it a bit, then back, just to make sure. Then I follow a straight line on that coordinate till the other lines up. I'm almost always within ten feet of the cache. Not always, I admit, but most of the time I'm pretty close.

 

I also like the idea of paying more attention to the terrain than to the GPS, looking for the obvious. I'm going to try that next time. There are several great ideas on this thread.

[+bigredmed]

I took my new Meridian out and had this happen. I wondered if it was due to my walking speed. I noticed that "auto averaging" was on. I don't know how to turn this off. Is it possible? My old 310 didn't seem to have this problem and my Magellan Companion doesn't seem to have this problem either.

 

By appointment to the Court of HRM Queen Mikki I.

[+Sluggo]

Hey Slower Pace,

 

Does that Maggie 315 work in ice fog?

 

If it does, be sure to set a waypoint at the car before you leave. That way when you overrun the car, you'll know it's there.

 

I'll get you back someday!

 

 

Unknown objects are operating under intelligent control... It is imperative that we learn where UFO's come from and what their purpose is... - -Admiral Roscoe H. Hillenkoetter Director, Central Intelligence Agency 1947-1950