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Re: [RFI] Compass Vectors

To: rfi@contesting.com
Subject: Re: [RFI] Compass Vectors
From: David Cole <dave@nk7z.net>
Reply-to: dave@nk7z.net
Date: Tue, 01 Dec 2015 07:47:27 -0800
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
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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