Grant,
Your information is incorrect. It is an
Equivalent Conic. The USGS
map may have the Central Meridian you quoted, but
it is based on the
Venezuelan Compensated Secant Conic on the Loma
Quintana Datum
of 1911 and not the Provisional South American
Datum of 1956.
The ellipsoid of reference is the Hayford 1909
(International 1924).
All of that is covered in great detail in the
December, 2000 issue of
"Photogrammetric Engineering and Remote Sensing,"
pages 1406-1408.
You may download my column from the Society's web
site listed
below my signature block. The late John P. Snyder
did help me
with that projection in 1988, and he may have
duplicated the
Venezuelan tabular error I discovered and
subsequently
discussed in my column.
Your question is answered on the first page of my
column.
Prof. Clifford J. Mugnier ([EMAIL PROTECTED])
Surveying, Geodesy, & Photogrammetry
LOUISIANA STATE UNIVERSITY
Department of Civil & Env. Engineering
2408 CEBA Building
Baton Rouge, Louisiana 70803
Voice & Facsimile: (225) 388-8536
====================================
See: http://www.ASPRS.org/resources.html
http://www.ce.lsu.edu/~mugnier/
====================================
----- Original Message -----
From: "Thomas, Grant (EXPLSAR)"
<[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, April 11, 2001 8:40 AM
Subject: MI-L Projections and Datums
> Hi
>
> I recently purchased a digital copy of the
Venezuelan Guyana Shield
> Geological Map from USGS.
>
> Readme file gave Projection as Equidistant
Conic:
> Sphere - Clarke 1866
> 1st parallel 9 0 0.000
> 2nd parallel 4 0 0.000
> Central Meridian -66 0 0.000
> Latitude origin 0.00000
> False easting (metres) 0.0000
> False northing (metres) 0.00000
>
> Although contacting the USGS and numerous
Internet sites I have not
> been
> able to ascertain the datum definition for the
map (possibly
> provisional
> South America). I would then enter definition
into MapInfo projection
> file.
>
> Is there site which lists known projection and
datum definitions -
> preferably MapInfo format?
>
>
> Grant Thomas
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