I've never seen that to be the case with mine. I've seen the unit lose the WAAS bird
at times, and it will toggle between SA and WAAS mode. It says what mode it's using
on the screen. I've never seen problems in heavy tree cover with mine. Or in general
anyway. I agree with one about the location of the WAAS birds. They are often lower
in the sky than the others, and if you loose one or two, the WAAS bird is often one
of the first to go. That may make it seem like WAAS is causing more error, but I think
it's the loss of the WAAS bird that causes more error, not having a weak but usable
WAAS bird in cover. Myself, I'd rather have the weak WAAS coverage, than no WAAS
coverage.
I often look at the sky map to see where the birds are in the sky. In many cases, the
WAAS bird is fairly low.
For me, I find my machine the most accurate when a lot of birds are almost directly
overhead, and have high WAAS coverage. And this seems to usually be in the middle of
the day for some reason. I notice at night, the bird coverage is often not quite as good,
and accuracy might suffer a tad. I don't know if this is a fluke, or by design when planning
the orbits of the birds.
I have land that is mostly wooded up in OK, and I've done a lot of testing up there.
Tree cover doesn't seem to bother my machine much at all. But mine also usually
works fine inside a car too.. As does my car GPS.
When mine is in real time WAAS mode, it will say WAAS..
When it loses the WAAS bird, or the coverage becomes spotty, it will say "WAAS average"
and show the amount of time that it's been in that mode. That elapsed time shows
how long it's been since a "good" WAAS fix. Often just changing the direction of the unit
and it's internal antenna will toggle it back and forth from WAAS to WAAS average mode.
So if I'm really wanting an accurate fix, I make sure I'm in WAAS mode, and it's stable
and not toggling back and forth.
I can measure off distances with mine, and have tested it at my property measuring
the distance between survey pins. I know the actual distances from the survey maps
of the property. If I let it get good and stable, and have a lot of overhead birds, it can
be right on the money for short periods of time. I'm talking measuring the pins right
down to the exact number of feet. But... it's all constantly "wobbling" around due to
the movement of the various birds. So I have to do a reset pretty often if I want it to
be real accurate. By reset, I mean that I set a new waypoint for the #1 pin, and then
hurry on down to the second one, let it get stable and see what it says.
The road frontage to my place is exactly 330 feet, and it will usually read out right on
the money with a stable unit, and fresh waypoints. But as you stand there, you
can see the fix wobble around a tad as you stand there a while. IE: I'll start out
right on the money, but then see it move north a few feet, wobble around to the
east a bit, duck behind me a while, etc.. It's never perfectly still..
But I trust mine more in WAAS mode, than in WAAS average mode. It's obviously
more accurate. And this usually applies to the elevation reading too..
Most all that place is heavy forest, and I never have trouble walking around the
place with trees constantly over me. I have saved "tracks" that show my property
lines. So I can wander around and know where my lines are even though I don't
have fences up. BTW, that's with an older Magellan Meridian. "yellow version".
Anyway, WAAS is supposed to be good to 3 meters or less. Mine often beats
that, and sometimes is right on the money for short periods of time after a fresh
set. In the overall scheme of things, and some error for various reasons, I
consider it to be accurate to about 5 feet in average use without trying to be
ultra accurate. But it's better than that if I do try to be ultra accurate..
