[Az-Geocaching] Help! Inaccurate Coordinates & Missing Cache

[Gordon L Flatt]

 http://www.cmtinc.com/gpsbook/chap7.html

There are several external sources which introduce errors into a GPS
position. While the errors affect accuracy, another major factor in
determining positional accuracy is the alignment, or geometry, of the group
of satellites (constellation) from which signals are being received. The
geometry of the constellation is evaluated for several factors, all of which
fall into the category of Dilution Of Precision, or DOP.

DOP
DOP is an indicator of the quality of the geometry of the satellite
constellation. Your computed position can vary depending on which satellites
you use for the measurement. Different satellite geometries can magnify or
lessen the errors in the error budget described above. A greater angle
between the satellites lowers the DOP, and provides a better measurement. A
higher DOP indicates poor satellite geometry, and an inferior measurement
configuration.

 Some GPS receivers can analyze the positions of the satellites available,
based upon the almanac, and choose those satellites with the best geometry
in order to make the DOP as low as possible. Another important GPS receiver
feature is to be able to ignore or eliminate GPS readings with DOP values
that exceed user-defined limits. Other GPS receivers may have the ability to
use all of the satellites in view, thus minimizing the DOP as much as
possible.


Gordon L. Flatt
AV Specialist
Smith Junior High
glflatt@mpsaz.org <mailto:glflatt@mpsaz.org>
480-472-4673




-----Original Message-----
From: az-geocaching-admin@listserv.azgeocaching.com
[mailto:az-geocaching-admin@listserv.azgeocaching.com]On Behalf Of
EvilFISH
Sent: Friday, April 23, 2004 3:35 PM
To: listserv@azgeocaching.com
Subject: Re: [Az-Geocaching] Help! Inaccurate Coordinates & Missing
Cache


first off aside from what the others do with the manual Garmin averaging, I
prefer to let my little Magellan sit for atleast a minute then let the units
self averaging do its thing for another minute, this has been the norm for
our over 25 caches I have only had to adjust the coords once, but that was
due to interference....
besides if the coords took you to zero everytime what fun would the 04/04/04
and Graldrichs caches be?

I agree with the 15 foot radius, that is pretty much the GPS norm.

as the Event cache and the ZERO experiment goes even the same units will be
off a little..


as far as cache plundering goes...

someone was curious to what was going on as they spotted a cacher caching.
this someone was greedy

someone found it by mistake and was greedy..





----- Original Message -----
From: "SquishyGecko" <squishygecko@yahoo.com>
To: <listserv@azgeocaching.com>
Sent: Friday, April 23, 2004 8:35 AM
Subject: [Az-Geocaching] Help! Inaccurate Coordinates & Missing Cache


> Recently Brian from Team A.I. posted a log entry to Gecko's Urban
Adventure
> in which he wrote that the coordinates were approximately thirty feet off
> from what I had posted on the listing.  Along with this, yesterday evening
I
> went venturing around checking some of my other caches, and noticed that
the
> coordinates, while close on some, where not so close on others.  Using a
> Magellan Meridian Gold now, is there any reason at all why this would be
> happening, and how do I make it stop happening?
>
> Also, I located one of my caches with the top hanging open and everything
> removed yesterday.  I recall some discussion about a pirate stealing from
> caches, however I thought that individual had been stopped.  Anyone have
any
> thoughts on this?  For the moment I've removed the cache, temporarily
> disabled it, and may put it back later.
>
> Thanks!
>
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