[Cdt-l] Cdt-l Digest, Vol 67, Issue 15

Todd Russell artnmotion at maine.rr.com
Sat Apr 13 19:56:10 CDT 2013 

Are we reading too much into this?  "Datum" is the singular form of  
"data."  Sorry to be too simple minded.

On Apr 13, 2013, at 8:42 PM, cdt-l-request at backcountry.net wrote:

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> Today's Topics:
>
>   1. Ley map datum? (Richard Lowery)
>   2. Re: Ley map datum? (Bob Sartini)
>   3. Re: Ley map datum? (Craig Johnston)
>   4. Re: Ley map datum? (Bob Bankhead)
>   5. Re: Ley map datum? (Jonathan Ley)
>   6. Re: Ley map datum? (bcss at bresnan.net)
>   7. Re: Ley map datum? (Jonathan Ley)
>   8. Re: Ley map datum? (bcss at bresnan.net)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 13 Apr 2013 15:26:57 -0700 (PDT)
> From: Richard Lowery <rlowery2007 at yahoo.com>
> Subject: [Cdt-l] Ley map datum?
> To: "cdt-l at backcountry.net" <cdt-l at backcountry.net>
> Message-ID:
> 	<1365892017.85804.YahooMailNeo at web160404.mail.bf1.yahoo.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Does anyone know what the datum is for the Ley maps?
> -------------- next part --------------
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> ------------------------------
>
> Message: 2
> Date: Sat, 13 Apr 2013 18:28:49 -0400
> From: Bob Sartini <bobsartini at gmail.com>
> Subject: Re: [Cdt-l] Ley map datum?
> To: Richard Lowery <rlowery2007 at yahoo.com>
> Cc: "cdt-l at backcountry.net" <cdt-l at backcountry.net>
> Message-ID:
> 	<CAAYFAemCNkkHcmy0yL=+7L_hZiUNJD0fR3OSvEVdM59TXOqQ2Q at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> 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?
>>
>> _______________________________________________
>> Cdt-l mailing list
>> Cdt-l at backcountry.net
>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>>
>
>
>
> -- 
> Everything is in Walking Distance
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 13 Apr 2013 16:43:10 -0600
> From: Craig Johnston <johnston73 at me.com>
> Subject: Re: [Cdt-l] Ley map datum?
> To: Bob Sartini <bobsartini at gmail.com>
> Cc: CDT Emaillist <Cdt-l at backcountry.net>
> Message-ID: <B4A81DC4-294C-4C1B-8F35-796FE0642424 at me.com>
> Content-Type: text/plain; charset=us-ascii
>
> I'm hiding under a rock in the desert I hope it means I'm very close  
> to lordsburg....
>
> Sent from my iPhone
>
> On Apr 13, 2013, at 4:28 PM, Bob Sartini <bobsartini at gmail.com> wrote:
>
>> 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?
>>>
>>> _______________________________________________
>>> Cdt-l mailing list
>>> Cdt-l at backcountry.net
>>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>>
>>
>>
>> -- 
>> Everything is in Walking Distance
>> _______________________________________________
>> Cdt-l mailing list
>> Cdt-l at backcountry.net
>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>
>
> ------------------------------
>
> Message: 4
> Date: Sat, 13 Apr 2013 15:59:17 -0700
> From: "Bob Bankhead" <wandering_bob at comcast.net>
> Subject: Re: [Cdt-l] Ley map datum?
> To: "'Bob Sartini'" <bobsartini at gmail.com>,	"'Richard Lowery'"
> 	<rlowery2007 at yahoo.com>
> Cc: cdt-l at backcountry.net
> Message-ID: <001401ce389a$870e1850$952a48f0$@comcast.net>
> Content-Type: text/plain;	charset="us-ascii"
>
> 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?
>>
>> _______________________________________________
>> Cdt-l mailing list
>> Cdt-l at backcountry.net
>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>>
>
>
>
> -- 
> Everything is in Walking Distance
> _______________________________________________
> Cdt-l mailing list
> Cdt-l at backcountry.net
> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>
>
>
> ------------------------------
>
> Message: 5
> Date: Sat, 13 Apr 2013 17:29:20 -0700
> From: Jonathan Ley <jonathan at phlumf.com>
> Subject: Re: [Cdt-l] Ley map datum?
> To: cdt-l at backcountry.net
> Message-ID: <5169F860.7010108 at phlumf.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> They're WGS84.
>
> It's kind of "the default" for most GPS uses these days.
>
> -Jonathan
>
> On 4/13/2013 3:59 PM, Bob Bankhead wrote:
>> 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?
>>>
>>> _______________________________________________
>>> Cdt-l mailing list
>>> Cdt-l at backcountry.net
>>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>>>
>>
>>
>
>
>
> ------------------------------
>
> Message: 6
> Date: Sat, 13 Apr 2013 18:28:58 -0600
> From: <bcss at bresnan.net>
> Subject: Re: [Cdt-l] Ley map datum?
> To: "'Bob Bankhead'" <wandering_bob at comcast.net>,	"'Bob Sartini'"
> 	<bobsartini at gmail.com>,	"'Richard Lowery'" <rlowery2007 at yahoo.com>
> Cc: cdt-l at backcountry.net
> Message-ID: <001501ce38a7$10c4cd30$324e6790$@net>
> Content-Type: text/plain;	charset="us-ascii"
>
> 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?
>>
>> _______________________________________________
>> Cdt-l mailing list
>> Cdt-l at backcountry.net
>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>>
>
>
>
> --
> Everything is in Walking Distance
> _______________________________________________
> Cdt-l mailing list
> Cdt-l at backcountry.net
> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>
> _______________________________________________
> Cdt-l mailing list
> Cdt-l at backcountry.net
> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>
>
>
> ------------------------------
>
> Message: 7
> Date: Sat, 13 Apr 2013 17:37:57 -0700
> From: Jonathan Ley <jonathan at phlumf.com>
> Subject: Re: [Cdt-l] Ley map datum?
> To: cdt-l at backcountry.net
> Message-ID: <5169FA65.3050901 at phlumf.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> The compass rose points are WGS 84... all pulled from outside sources,
> and manually aligned with points on the maps.
>
> Anyway, a few hundred feet of accuracy isn't going to matter for the
> compass rose method. You should not need (or expect) any more than  
> ~1/4
> mile accuracy if you're using that method. It's just to figure out
> "about where you are" on the maps... after doing that, you can just  
> use
> cerebral navigational techniques to determine a more accurate  
> location.
>
> -Jonathan
>
>
> On 4/13/2013 5:28 PM, bcss at bresnan.net wrote:
>> 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?
>>>
>>> _______________________________________________
>>> Cdt-l mailing list
>>> Cdt-l at backcountry.net
>>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>>>
>>
>>
>> --
>> Everything is in Walking Distance
>> _______________________________________________
>> Cdt-l mailing list
>> Cdt-l at backcountry.net
>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>>
>> _______________________________________________
>> Cdt-l mailing list
>> Cdt-l at backcountry.net
>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>>
>> _______________________________________________
>> Cdt-l mailing list
>> Cdt-l at backcountry.net
>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>>
>>
>
>
>
> ------------------------------
>
> Message: 8
> Date: Sat, 13 Apr 2013 18:39:52 -0600
> From: <bcss at bresnan.net>
> Subject: Re: [Cdt-l] Ley map datum?
> To: <jonathan at phlumf.com>,	<cdt-l at backcountry.net>
> Message-ID: <001601ce38a8$967d7a70$c3786f50$@net>
> Content-Type: text/plain;	charset="us-ascii"
>
> Regardless, the 100' between NAD27 and WGS84 should not be a deal  
> breaker
> for a hiker. The trail line on most maps is almost 100' wide.
>
>
> 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 Jonathan Ley
> Sent: Saturday, April 13, 2013 6:29 PM
> To: cdt-l at backcountry.net
> Subject: Re: [Cdt-l] Ley map datum?
>
> They're WGS84.
>
> It's kind of "the default" for most GPS uses these days.
>
> -Jonathan
>
> On 4/13/2013 3:59 PM, Bob Bankhead wrote:
>> 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?
>>>
>>> _______________________________________________
>>> Cdt-l mailing list
>>> Cdt-l at backcountry.net
>>> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>>>
>>
>>
>
> _______________________________________________
> Cdt-l mailing list
> Cdt-l at backcountry.net
> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>
>
>
> ------------------------------
>
> _______________________________________________
> Cdt-l mailing list
> Cdt-l at backcountry.net
> http://mailman.backcountry.net/mailman/listinfo/cdt-l
>
>
> End of Cdt-l Digest, Vol 67, Issue 15
> *************************************

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