David: Yes, I was a bit redundant, but I wanted to emphasize that there can
be substantial and very localized variations in the declination that differ
from the predictions. 73, Mike, WV2ZOW
On Tue, Dec 1, 2015 at 10:47 AM, David Cole <dave@nk7z.net> wrote:
> I thought I said that...
> --
> Thanks and 73's,
> For equipment, and software setups and reviews see:
> www.nk7z.net
>
> For MixW support see;
> http://groups.yahoo.com/neo/groups/mixw/info
> For Dopplergram information see:
> http://groups.yahoo.com/neo/groups/dopplergram/info
> For MM-SSTV see:
> http://groups.yahoo.com/neo/groups/MM-SSTV/info
>
>
> On Tue, 2015-12-01 at 10:32 -0500, Michael Clarson wrote:
> > Another caution: Magnetic "North" can vary substantially from the
> > predicted declination. I always calibrate my compass by sighting a
> > physical object and comparing the bearing to a map. I learned this
> > while trying to aim a microwave antenna on top of a ridge between
> > Bethlehem and Harrisburg PA. Mountain loaded with iron ore. My compass
> > was about 30 degrees off! This mountain is one of the few places on
> > Earth where one's compass can be off that much due to local
> > conditions. --Mike, WV2ZOW
> >
> > On Tue, Dec 1, 2015 at 9:01 AM, David Cole <dave@nk7z.net> wrote:
> > If you are doing this by hand, as I do, then remember, to keep
> > the map
> > and your bearings, in either True, or Magnetic North, I always
> > keep my
> > maps in True North, and adjust my compass readings to True
> > North, prior
> > to plotting them.
> >
> > If you take a Google map, it will be True North, while your
> > uncompensated compass, will be in Magnetic North. I use
> > Google Earth
> > images to draw my plots on.
> >
> > You need to convert both your map, and your readings to the
> > same units,
> > either True or Magnetic North, before you draw a bearing line
> > on your
> > True North oriented Google map. Here is how I get them to
> > match the the
> > easy no math way.
> >
> > I go here: http://www.acscdg.com/ and get a map of a long,
> > straight,
> > road that runs dead N, S, E, or W in my area, the actual
> > bearing does
> > not matter, it only matters that you know the bearing of the
> > road
> > exactly, and can read your compass to that same accuracy,
> > hence why I
> > use N, S, E, or W, they are easy to find on a compass, and
> > almost every
> > city has N/S/E/W roads.
> >
> > I pick a road that is long, and has a sidewalk, that way I can
> > stand on
> > the sidewalk, and sight down the sidewalk, not looking off to
> > the side
> > and sighting down the road from the sidewalk, thus introducing
> > parallax
> > issues. I then take my compass to that road, and sight down
> > the
> > sidewalk.
> >
> > I purchased an adjustable compass so I just adjust the compass
> > to read
> > the heading of the road, and my compass is now calibrated to
> > True
> > North.
> >
> > See: http://www.ngdc.noaa.gov/geomag/declination.shtml for why
> > you need
> > to do this...
> >
> > I then go home and take a bearing on something far away, from
> > a known
> > spot on my property, and write that bearing down. Then the
> > next time I
> > go out and start looking for RFI, I just sight on the object
> > again, from
> > the same spot, and adjust the compass if it has moved... I'm
> > now all
> > set to do True North bearing drawings...
> >
> >
> > --
> > Thanks and 73's,
> > For equipment, and software setups and reviews see:
> > www.nk7z.net
> >
> > For MixW support see;
> > http://groups.yahoo.com/neo/groups/mixw/info
> > For Dopplergram information see:
> > http://groups.yahoo.com/neo/groups/dopplergram/info
> > For MM-SSTV see:
> > http://groups.yahoo.com/neo/groups/MM-SSTV/info
> >
> >
> > On Tue, 2015-12-01 at 02:18 -0500, Roger (K8RI) wrote:
> > > Select your area with as much resolution as possible.
> > > Drive to a location, take a bearing. using the Google
> > distance ruler,
> > > draw a line through your point. Drive to another point and
> > repeat. Two
> > > bearings are often sufficient, but three leave a small
> > diamond for the
> > > region of error. Much easier to do than explain, although
> > there is a
> > > learning curve.
> > >
> > > It gets messy with RFI hunting when there are multiple
> > sources, with
> > > overlapping and similar patterns as in multiple networks or
> > an area
> > > where there are a mix og cable and outside antenna and the
> > users just
> > > wired the preamps and cable together. This sometimes can
> > lead to a much
> > > larger region of error.
> > >
> > > 73 es good luck
> > >
> > > Roger (K8RI)
> > >
> > >
> > > On 11/30/2015 8:16 PM, Karin Johnson wrote:
> > > > I'm planning on doing some RFI hunting and wanted to know
> > if anyone
> > > > knows how to plot compass vectors on Google Maps?
> > > > I need to plot intersecting vectors from a direction
> > finding loop to
> > > > find the source of an RFI generator.
> > > >
> > > > Karin K3UU
> > > > Palm Harbor, FL
> > > >
> > > > _______________________________________________
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> > > >
> > >
> > >
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