From: David E. DeLano (david.delano@cox.net)
Date: Thu Jul 18 2002 - 16:51:47 CDT
> I did however quit trying to be precise on my entering waypoints from =
> the maps. I should have been able to locate camps within 100 feet. =
> Again, not even close. I will confess that most of my pre planning was =
> done from a prior generation map. I have not yet compared the newer =
> ones to the old, but I suspect they were the same.
I was going to try to stay out of this one, but.....
I had 3-4 sources of waypoints that I used before I left for Philmont. I plotted all of these on TopoUSA and hardly any of them correlated with each other. However, using these as reference, using the TopoUSA map, and using a set of Quad 3-D maps, which TopoUSA 4.0 can display side-by-side, I came up with about 80 waypoints in the "south" part of Philmont.
I used the GPS to plot our progress, and when I got home, I plotted it back onto TopoUSA. Aside from missing points, the data was fairly close to any mapped trails.
When the day started I would clear the totals, and do a goto to the next destination. If there were several waypoints available, I did a quick route (this only happened a couple of days). Off and on during the day, I'd check our progress. I marked new waypoints at our destinations to check later. Since I'm with a Venturing Crew, which has a requirement to use GPSs, there were times the navigator would request a coordinate, which was used to "find" us on the map. Otherwise, the GPS was for my personal use.
The waypoints I put in were all well within a reasonable margin of what I'd expect. There is some variation in accuracy from the satellites. Also, most of the sites I marked are large places. I tried to be consistent, like in front of the porch of a staff camp, or at the central map of a trail camp. However, the map, and other people, may have marked different places.
Now, if ALL your waypoints were consistently off, then I'd suspect you have a datum problem. Most GPSs default to WGS80. Most maps are NAD27. If you don't match the two of them, you are never going to be as accurate as you like. Granted, these spots are only a few hundred feet apart, but that's not what most people expect.
When I analyzed my data when I returned home, the waypoints I marked were within 50' of the ones I had loaded. Some were even closer, with a couple dead on.
Hope this helps.
David DeLano
627H2
VC124, Phoenix, AZ
-------------------------------------------------------
Scouting E-mail Discussion Lists @ usscouts.org
Subscribe/Unsubscribe at http://usscouts.org/lists/
Listserv Commands at http://usscouts.org/lists/lc.asp
-------------------------------------------------------
Send listserv commands to: listserv@troop47.com
Send postings to: philmont@troop47.com
List FAQ found at: http://usscouts.org/lists/faq.asp
List Administrator: philmont_owner@troop47.com
-------------------------------------------------------
As you gather around this virtual campfire with fellow
Scouts and Scouters, do your best to be trustworthy,
loyal, helpful, friendly, courteous, kind, obedient,
cheerful, thrifty, brave, clean and reverent.
-------------------------------------------------------
This archive was generated by hypermail 2.1.7 : Thu Mar 13 2003 - 10:38:05 CST