On Nov 26, 9:25*pm, Jeff Liebermann wrote:
On Thu, 26 Nov 2009 20:28:51 -0800 (PST), "

wrote:
http://www.cammenga.com/cammenga-pro...php?category=1
The phosphorus version is good enough. I "juice it" with a flashlight
since I'm not working SWAT or special ops. ;-) *You can pay extra for
tritium, but it wears out. You shouldn't buy one used for that reason.
The phosphorus version is under $40 and it will last a lifetime, or
until it is lost or stolen.

Yech. *I do some TV antenna alignments and the usual point to point
wireless. *I don't bother with a compass because they're not accurate
enough. *What works best is a road map, a plywood board, and some
nails. *Mark your position on the map with a nail, push pin, or pin.
Mark the position of a distant mountain, building, or landmark on the
map. *Eyeball the line between the two nails to the distant mountain,
building or landmark. *All maps have true north marked on them. *The
direction of the map arrow is true north. *I can usually locate true
north to within +/- 2 degrees depending on the size of the map and the
distance to the marker. *Using multiple distant points improves the
accuracy.

If you're into astronomy, sighting the north star also works well.
Also, using a computer sky chart/map to locate easy to find stars.

One I establish true north, I like to mark it on the road, sidewalk,
or deck with a line or arrow. *I have a brass marker arrow nailed to
my deck.

I have a GPS with a compass in it, but you have to remember to
calibrate them. Really annoying.

Calibrate? *You have to be moving in order for it to work. *Then, it
will only tell you the direction that you're moving. *If you only go a
short distance, it's not going to be very accurate.

Next up of course is that damn magnetic correction.

I don't do no stinkin magnetic correction cause I don't use no stinkin
magnetic or fluxgate compass.

Incidentally, I have a really handy item for watching expensive birds.
I made a panorama (stitched) photo of the view from my rooftop at
home, at the office, and at my favorite astronomy meeting places. *I
then marked the azimuths every 10 degrees on the JPG. *Although
difficult to see the remote hilltops at night, I now have the azimuth
of anything in the sky or between me and the surrounding hills.

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

The "virtual" compass requires you to move since it bases direction on
differential GPS readings. OK in a car, semi-OK on foot, worthless if
the going is slow since the delta of distance is not significant
enough to get a good calculation.

The newer GPSs have sensors in them. To null out the nearby magnetic
field, you need to slow spin it around. Two revolutions generally. Or
you can spin your body around and look like an idiot. The trouble is
the GPS has to be level unless you have a 3-D compass. [Garmin
doesn't, Magellan does. Too many complaints about Magellan gear, so
you just put up with Garmin.] The GPS has a threshold where it will
shift from magnetic sensor to virtual compass. You can really screw
yourself up if you don't know about this.

Your technique is fine if you spot from the same location. If you are
on the move, you realy do need a compass. Occasionally I'll see
something off in the distance.[OK, OK, in denied access area.] Log
your position, take a vector, then study it on google earth or a map.
Other times I am DFing radio signals. Again, the compass does the log.
Log everything in magnetic, then use your mag in magnetic, and you
won't go crazy. Attempt to correct your readings and you are either
correct or you just added twice the adjustment factor to your reading.
Really not a good idea.

Aviation long ago decided on doing everything magnetic, probably to
get around the confusion. Of course, they still use AGL (above ground
level) and MSL (mean sea level) for altitude. You may recall either a
Thunderbird or Blue Angel getting into trouble with this.

I use your spotting technique at times too. It depends on if I can do
the preparation. Your scheme works better in mountain areas, which is
where I use it since I know the various peaks and where the campsite
is located.