[GeoStL] Re: Perfection is hard to achieve
- From: Mike Lusicic <lusicic@xxxxxxxxxxxxx>
- To: geocaching@xxxxxxxxxxxxx
- Date: Wed, 02 May 2007 17:17:41 -0500
-
This is not a definitive answer.
I know that the photo view in GE is based on photos taken from an airplane.
If you look at trees and object, you get a view other than straight down
fromthe top. That means that at least SOME of the photos introduce an error
because you are not looking straight down. Therefore, the angular view means
that a scale is not accurate because the view angle at any given point
depends on where the airplane was when it took the picture. So the scale
directly under the airplane is not the same as at the border of the frame of
the mosaic shot that was taken. So I would assume there is some error in GE,
and correcting the error would require knowing the position of the airplane
when it took the shot, its altitude, the type of lens used (fisheye etc.)
andother factors I would only be guessing at. My hunch is that they are not
going to go through that much trouble even if they knew all of this
information. I am not sure how much error this actually introduces, so I
can't give you a + or - error limit.
I would think that the GPS might be set up to consider the types of
variablesit has to deal with, and will at least give you the +- accuracy of
what it is showing you.
My 2 cents, and it probably isn't worth even that much.
RNX wrote: - I"m not t= alking about using the GE KML to find a cache. I
know that they intention= ally move the cache icon to preserve the thrill of
the hunt. My question = was more pointed to using the pointer coordinates
that are indicated by G= E when hovering over a landmark. I know that my
GPSris generally +/- 15 = feet. Just doing a survey to see if it is
generallyaccepted that GE has = better acuracy or not? I guess to come at
this question from another dire= ction; When i manually enter the published
coordinates for one of my cach= es into GE, it marks a point almost 15ft
awayfrom the landmark where i k= now the cache is hidden. Which application
would you trust as the higher = authority? GE or a Garmin GPSr with a 1000
ping average? ------ Original Message ------ Received: Wed, 02 May 2007
05:29:34 PM EDT From: Mike Lusicic <lusicic@xxxxxxxxxxxxx>[1] To:
geocaching@xxxxxxxxxxxxx[2] Subject: [GeoStL] Re: Perfection is hard to
achieve - If you are talking about the service where GE puts caches on the
ma= p, then Ithink that there is a disclaimer about the accuracy not being
very= good. I have seen caches move around as you zoom in and out on GE. On
the other hand, if you are manually entering the coordinates on = a cache
page, then those are the hider's coordinates, and GE isn't going to= do
anything to improve the situation. If anything, based on the discla= imer,
itmay introduce its own error. If you are looking at an aerial view and
usinglandmarks to determi= ne coordinates for a hide, I am not sure how
accurate that is. They ha= ve impose coordinate over a photo, and depending
on the area, the resolution = isn't thatgreat, and depending on the angle
thephoto is taken, the scale= isn't necessarily linear, so there will be
someerror introduced there, b= ut I don'tknow how much. I think in the long
run, the GPSr on location m= ay be the best bet. BTW, those are not
satelliteviews. They are taken from aircraft fl= ying over the area. RNX
wrote: - Does a=3D nyone have an opinion on the acuracy of Goog= le Earth?
Ifi c=3D an zoom in and see the cache location, place my pointer o= n
tha=3Dtpoint, can i assume that the designated coordinates are mo=3D re ac=
urate than my GPSr's? I know there's still the error =3D of the finder's
unit= to be accounted for, but at least the hi=3D der's error has been
minimize= d. ------ Original Message ------ Received: Wed, 02 May 2007
04:29:57 PM EDT = From: MikeLusicic <lusicic@xxxxxxxxxxxxx>[3][1] To:
geocaching@freelis= ts.org[2] Subject: [GeoStL] Re: Perfection is hard to
achieve - Well, most fo= lks look at only the accuracy of their GPSr (from
my=3D experiencein showing= folks), assuming the published coordinates a=3D
re accurate.Even with 15 fo= ot accuracy,if the hider is off 15 feet =3D to
the left and the finder= is 15 feet off to the left of that, then that is
3=3D 0 feet without even 30 f= oot accuracyshowing on your GPSr. If both
units=3D are only getting 30 = foot accuracy, then you could be 60 feet
away.Of cour=3D se that is the= most extreme example. Of course the better
the hider can do, =3D the les= s he is going to contribute to the error,
thusthe method Steve was re=3D c= ommending for establishing the cache
coordinates. Andrew Senger wrote: - I ha= ve to remind my dad (lobocs) of
this a=3D ll the time.Frequently, his GPS= r will come to a different
location than =3D mine, and he'll still look just in= his area (even with a
22-30 foot accurac=3D y!). I can easily count several = times the cache was
away from both of our "Z=3D ero" points,so I've learned t= o start looking
around from there. Andrew=3D (yawetag) On 5/2/07, Laura Mil= lion
<lmillio@xxxxxxxx>[4][3][1] wrote: - Whe=3D n I'm caching withne= w people
orwhen teaching the Girl Scouts, I tell them that=3D the GPS is only a too=
lthat will take them to the area of the cache. Once th=3D ey get to the
area,= they should put the GPS down and start using their eyes=3D and brains
to look. = Look for things out of place like a pile of sticks or le=3D aves
that would = not have fallen there naturally. Look for little nooks and =3D
holes that mi= ght hold small containers. Look high as well as low since
some=3D of those = devious cachers don't always place their caches on the
ground. My=3D GPSr i= s often way off. That's what I get for buying it on
E-bay. I also u=3D se a mag= netic compass because my needle on the GPS
mightbe pointing s=3D outh, b= ut I know that that direction is really
north.I'll pull out my compas=3D s a= nd find whatis really south and follow
that. It has helped me often. Lau=3D= ra Million Faculty Technology Center
ftc_help@xxxxxxxx[2[4[5]]] 618-650-5697 To s= u=3D bmit a work request
pleaseemail ftc_help@xxxxxxxx[3[5[6]]] For questions or = help w=3D ith
Blackboard please visit:
http://www.siue.edu/lovejoylibrary/ftc/bb_tutorials.shtml[4[6[7]]] ---= -=3D
-Original Message----- From: geocaching-bounce@xxxxxxxxxxxxx[5[7[8]]]
[mailto:geocaching-bounce@xxxxxxxxxxxxx[6[8[9]]]] On Behalf Of Stephen= =3D
Martin Sent:Tuesday, May 01, 2007 7:25 PM To:
geocaching@xxxxxxxxxxxxx[7=3D=[10[9] ] Subject: [GeoStL] Perfection is hard
to achieve - I am curious abou= t some =3D things that are actually geocache
related... sorry no food this tim= e. I have =3D experienced several
incidents of people pointing out that a cac= he is off by2=3D 0 to 50 feet.
Sometimes it has been regarding one of my hide= s, sometimes=3D the logs of
acache I am hunting, and I have witnessed= it on some races. I be=3D lieve
that there are many reasons for that including= terrain andfoilage, we=3D
ather, sattelite position and the difference in G= PSrs. Therefore, I
watc=3Dh the needleuntil I get to a zero and just sea= rch outward from
there. I=3D think that is the fun part... the search. How fun = is pin the
tail on the don=3D key if your hand guides you to the exact spot. W= here is
the challenge? Most o=3D ften the difference is 30 feet or less, and ge=
oexperience should teach whe=3D re to look. I would love feedback on this
issue= =2E Am I atleast partly correct =3D for causes of descrepencies? Is
the it t= he hunt not the needle that rocks? T=3D hanks for any response to
my random tho= ughts. Happyhunting! Stephen BTW- T=3D he picnic looked to be
a huge succe= ss from the look of the photos. Illness =3D kept me away.
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