[meteorite-list] I'm getting confused by the MB coordinates

From: Chris Peterson <clp_at_meteoritecentral.com>
Date: Sat Aug 26 10:28:08 2006
Message-ID: <087801c6c91b$ce0657e0$2721500a_at_bellatrix>

A systematic coordinate error is a possibility, but don't look at the
choice of map datum as the problem. At most, various datums will differ
by a few hundred meters. A four mile error has to come from somewhere
else.

A map datum is a model based on some mathematical approximation of the
shape of the Earth. Because it isn't spherical, the choice of
mathematical function used to describe it slightly affects topocentric
coordinates.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message -----
From: "Walter L. Newton" <newtonw2_at_comcast.net>
To: <meteorite-list_at_meteoritecentral.com>
Sent: Saturday, August 26, 2006 12:34 AM
Subject: [meteorite-list] I'm getting confused by the MB coordinates


> Hi
>
> Some of you may have remember being bored by my running dialog with
> the MB
> and Jeff in reference to the actual find spot of a Colorado meteorite.
>
> In the MB, the Apex Colorado meteorite has coordinates that puts the
> find
> (1938) at about 4 miles north of the actual location. I know the
> actual
> location because of the narrative in the MB, and Jack Murphy concurs.
> He
> knows where it was found and it's not where the MB coordinates have
> it.
>
> Now... a have a new girlfriend (yes, this is really going somewhere)
> and
> Steffanie lives in Russell Gulch Colorado, which is an old mining town
> south
> and above Central City Colorado. It's listed as a ghost town even
> though it
> has about 35 folks living there.
>
> Well, looking at the MB list of Colorado meteorites, low and behold,
> we have
> a Russell Gulch meteorite, an iron, found in 1863.
>
> But, if you check the coordinates with Google Earth, the find spot
> would be
> right in Central City Colorado... about 4 miles north of Russell
> Gulch.
>
> Do we see a pattern here. Steff is going to hook me up with an old
> timer
> that lives in Russell Gulch, who knows about the find and has a good
> idea
> where it was found.
>
> My question is (I promised this was going somewhere)... was some of
> the
> coordinates in the MB constructed from a different map datum. I
> vaguely
> remember something about different datum sets used for lat. and long.
> I
> don't really understand the details about this, but I know my simple
> GPS
> unit has a whole list of datum sets that I can set my unit to.
>
> Are the MB coordinates really right, but using a different "starting
> point"
> then Google Earth.
>
> Otherwise, I guess I'm going to go off on another tangent with the MB
> about
> another find spot.
>
> Maybe someone can point me to an online article that explains all
> this?
>
> I know this is not as earth shattering as losing a whole planet, but
> it bugs
> me none the less.
>
> Stop me before it's too late. (did this make any sense?)
>
> Walter L. Newton
> Golden, Co
Received on Sat 26 Aug 2006 10:27:47 AM PDT