From: Signe Rogers (HikinMama@iglide.net)
Date: Fri Jul 19 2002 - 07:57:00 CDT
Yes, map datum is a critical element of GPS usage. I used NAD27 and
found my waypoints to be accurate most of the time. The ones that were
off were when I was plotting locations of windmills showing up on the
map & I what the map shows as windmills were off. (This was true of the
first one N of Rich Cabins, the one in Beaty Meadow, and the one in
Whiteman Vega.)
I used the NAD27 for datum setting based upon the fact that at
www.topozone.com those maps match exactly what I find on the Philmont
maps, even naming most of the camps that you find on a Phil map. The
Topozone datum is NAD27. I also note that at the bottom of the Central
map, there is a note that says it is based on datum of 1929. I don't
recall all the research I did a year ago for verification, but I came to
the satisfied conclusion that using NAD27 datum was the accurate choice
based upon the 1929 datum.
When I was preparing for the trek, I cyber trekked on Topozone with my
hard copy PHilmaps beside me for reference. These were the coordinates I
started my trek with & like I said, *most* were close - close enough
that were I to be completely lost out there, I am certain I would have
found my way to the ballpark where I would expect people to be -
evidenced by the fact that we did ample schacking in the Valle where
that is encouraged & we found our way to the staffed camps from the
middle of nowhere! Again, we were a Venturing Crew & we did use the GPS
as a primary navigational tool with the youth gaining a proficiency in
GPS use in earning their Ranger Award.
Signe Rogers
-----Original Message-----
From: owner-philmont@troop47.com [mailto:owner-philmont@troop47.com] On
Behalf Of Alan R. Hamm
For the record, my datum was set to WGS84. If you can find a different
setting on a Philmont map, I would love to see it. I looked several
times.
I was very surprised there was no reference to a datum on the maps.....
The difference may be Datums for the plotting of waypoints accurately.
WGS84 vs. NAD27 maybe. I tried to find a datum on the maps to no avail.
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