[San-Diego-pm] Meeting today (Monday, March 13th, 2006)

Joel Fentin joel at fentin.com
Tue Mar 14 21:12:25 PST 2006

Tkil wrote:

> Most of the maps from the USGS for years have been based off the North
> American Datum from 1927 ("NAD27").  GPS is based off the World
> Geodetic System 1984 ("WGS84").

My GPS is the same one the Wright Brothers used at Kittyhawk.

1. Because the local USGS topo maps are NAD27, that's what I have my GPS 
set to. More specifically NAD27 CONUS. (There are lots of NAD27s.)

2. Because UTMs are handier to use than Lat-Lon, that too is what I use.

3. Google Earth uses Lat-Lon. And perhaps they use WGS84. The error I 
saw was in the neighborhood of a long block or two. A football field or two.

4. Next time I'm at a location with a faster connection that 24K dialup, 
I'll switch my GPS to Lat-Lon and WGS84 and see if that cleans off the 
error. If so, I will have gotten an eduction and I can then continue 
with what I set out to do in the first place.


And speaking of education, thanks for the doctorate by email. I'll save 
your email for future reference.

I have two USGS maps of the desert that are more than 100 years old. You 
can see the railroad lines running through what is now the Salton Sea, 
and the spellings have changed. Is this something that would interest you?

Considering what those poor bastards had to endure back then, I think 
they did a stupendous job surveying.
So much for Perl.
Joel Fentin       tel: 760-749-8863    FAX: 760-749-8864
Email me:         http://fentin.com/me/ContactMe.html
Biz Website:      http://fentin.com
Personal Website: http://fentin.com/me

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