[Cdt-l] Ley map datum?

bcss at bresnan.net bcss at bresnan.net
Sat Apr 13 19:28:58 CDT 2013


Jonathan's maps are reproductions of USGS Topo sheets which were projected
in NAD27 (North American Datum of 1927).  The NAD27 coordinate system
disagrees with WGS84 (World Geodetic System of 1984 - the native language of
gps) by up to 150'. Differences of 100' are normal. If you used a WGS84
background map to calibrate a NAD27 map image, expect errors in that range.



best wishes,

Jerry Brown
(970) 403-3527    Cell: (970) 749-0496
mailto:bcss at bresnan.net
www.bearcreeksurvey.com

-----Original Message-----
From: cdt-l-bounces at backcountry.net [mailto:cdt-l-bounces at backcountry.net]
On Behalf Of Bob Bankhead
Sent: Saturday, April 13, 2013 4:59 PM
To: 'Bob Sartini'; 'Richard Lowery'
Cc: cdt-l at backcountry.net
Subject: Re: [Cdt-l] Ley map datum?

The National Geodetic Survey defines a geodetic datum as "a set of constants
specifying the coordinate system used for geodetic control, i.e., for
calculating the coordinates of points on the earth."

Basically, it defines how the GPS coordinates are determined. Hence the
terms NAD 1927, NAD 1983, and WGS 84.

For more than you'd ever want to know, go to:

http (colon)//staff(dot)bcc(dot)edu/mzamkoto/ppt_gis/Datums(dot)pdf

-----Original Message-----
From: cdt-l-bounces at backcountry.net [mailto:cdt-l-bounces at backcountry.net]
On Behalf Of Bob Sartini
Sent: Saturday, April 13, 2013 3:29 PM
To: Richard Lowery
Cc: cdt-l at backcountry.net
Subject: Re: [Cdt-l] Ley map datum?

Does anyone know what datum means?

On Sat, Apr 13, 2013 at 6:26 PM, Richard Lowery <rlowery2007 at yahoo.com>
wrote:
> Does anyone know what the datum is for the Ley maps?
>
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Everything is in Walking Distance
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