Re: MAP DIFFERENCES
- From: bobbrooks220@xxxxxxxxx
- Date: Thu, 26 Jul 2007 02:54:54 -0700
On Jul 26, 3:37 am, Happy Trails <nom...@xxxxxxxxxxx> wrote:
On Wed, 25 Jul 2007 18:25:12 -0700, bobbrooks...@xxxxxxxxx wrote:
I remembered that there was a survey marker on the peak of a small
mountain in my area so I went up tonight and found it. Unfortunately
time has worn away all the information. I had an interesting
exsperience though. I used TopoZone coordinates for the peak and wound
up about 100 feet lower down the side of the mountain deep in a patch
of juniper before zeroing out. I then went back to the marker which I
assume is the very top and put in a waypoint, averaged it, went to MAP
and found that my waypoint was 61 feet from the Mapsource symbol for
the peak. When I got home I put the coordinates into Terrain
Navigator's USGS map which showed the field waypoint (76CSx) right on
the money. Any thoughts on why all three programs are so different?
Especially the Topo Zone which was way off.
Are you saying that you have 2 different coordinates for the same
point taken from theoretically precise sources?
Or are you spooked because you have just discovered that your $300
handheld GPS receiver is not always as precise as a $50,000 survey
setup, nor as precise as the sales literature would have you believe?
The datums were all NAD 27, both distances were horizontal. I was
surprised that the three mapping programs had three different
coordinates for the same spot. Trying to figure out what to expect
from the unit, maps, etc. and its been a trip (pun intended). I
appreciate the education I'm getting from this group.
.
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