non-directional navigation beacon location techique question
 

I'm trying to find the location of a low frequency mavigation beacon.
Two techniques come to mind.

1) Using the null of a loop antenna, find a vector to the beacon using
a compass. Note the location where the vector was found on a GPS. Do
this from multiple locations and the beacon is where the lines
intersect. Since there will be error in both the compass (2 degrees
using a Garmin GPS) and some error in finding the null, the result will
be more of a locus of points where the beacon could be located rather
than the beacon itself.

2) Again from various locations, find the direction of the unknown
beacon and a known beacon (about 40 miles apart). Use a turntable of
sorts to find the number of degrees between the known and unknown
beacon. [Note, this will not require a compass, just an angular
measurement) Given the angle difference between the two beacons, a
vector can be drawn from a well known (via gps) location. Again, where
these vectors intersect is the location of the unknown beacon.

Throw into the mix one more reference. It should be possible to find a
spot where both beacons null at the same time. The the unknown beacon
is along a line between your location and the known beacon. This would
be a line that should be quite accurate. This should be doable from two
locations, i.e one where the known beacon is the closer of the two, and
the opposite situation.

Comments, besides get a life?

wrote:

I'm trying to find the location of a low frequency mavigation beacon.
Two techniques come to mind.

1) Using the null of a loop antenna, find a vector to the beacon using
a compass. Note the location where the vector was found on a GPS. Do
this from multiple locations and the beacon is where the lines
intersect. Since there will be error in both the compass (2 degrees
using a Garmin GPS) and some error in finding the null, the result will
be more of a locus of points where the beacon could be located rather
than the beacon itself.

2) Again from various locations, find the direction of the unknown
beacon and a known beacon (about 40 miles apart). Use a turntable of
sorts to find the number of degrees between the known and unknown
beacon. [Note, this will not require a compass, just an angular
measurement) Given the angle difference between the two beacons, a
vector can be drawn from a well known (via gps) location. Again, where
these vectors intersect is the location of the unknown beacon.

Throw into the mix one more reference. It should be possible to find a
spot where both beacons null at the same time. The the unknown beacon
is along a line between your location and the known beacon. This would
be a line that should be quite accurate. This should be doable from two
locations, i.e one where the known beacon is the closer of the two, and
the opposite situation.

Comments, besides get a life?

The easiest way by far is to look up its location - no point in having a
navigation beacon if you don't publish the location.

Dave

This particular beacon is somewhere around Area 12 on the Nevada Test
Site. It is not published.

There are three unpublished NDB in the general area.
209Khz AEC located at Basecamp (near route 6 east of Warm Springs)
http://www.lazygranch.com/sound/beac...ecamp209_2.wav
278Khz XSD located at the north end of the Tonopah Test Range
www.lazygranch.com/sound/beacons/xsd278.wav
414Khz PYD somewhere near Area 12 on the Nevada Test Site
www.lazygranch.com/sound/beacons/pyd414.wav

Needless to say, these are not FCC licensed.

One more though comes to mind. Would it make sense to use a narrow band
filter (say a CW filter) on the beacon when determining the null since
the S meter will be used to determine the minimum signal strength.

One more though comes to mind. Would it make sense to use a narrow band
filter (say a CW filter) on the beacon when determining the null since
the S meter will be used to determine the minimum signal strength.

I have a Bendix 555 marine RDF, but the null is no where near as good
as using a loop with a Welbrook amp. Further, you really don't know the
bearing any better than a compass reading. That is, you can get the RDF
to point at the source (via a null), but that information needs to be
associated with a compass reading. Essentially, this is method one that
I listed.

On 9 Apr 2005 19:34:13 -0700, wrote:

I'm trying to find the location of a low frequency mavigation beacon.
Two techniques come to mind.

1) Using the null of a loop antenna, find a vector to the beacon using
a compass.

2) Again from various locations, find the direction of the unknown
beacon and a known beacon (about 40 miles apart). Use a turntable of
sorts to find the number of degrees between the known and unknown
beacon.

Throw into the mix one more reference. It should be possible to find a
spot where both beacons null at the same time.

Comments, besides get a life?

Sounds like an interesting project. Why not use all three techniques
together? After all, you are trying to locate something as accurately
as you can - all the data you collect is relevant to solving the
problem.

The poistion polygon that you will determine used to be known as a
'cocked hat' - the smaller it is, the better your determination. There
used to be an expression "I knocked him into a cocked hat', meaning
that you had negated someone's argument. Good luck.

1) Using the null of a loop antenna, find a vector to the beacon using
a compass. Note the location where the vector was found on a GPS. Do
this from multiple locations and the beacon is where the lines
intersect. Since there will be error in both the compass (2 degrees
using a Garmin GPS) and some error in finding the null, the result will
be more of a locus of points where the beacon could be located rather
than the beacon itself.


I have posted a law-of-cosines calculation example several times where
coordinates of an intersection point are determined from two GPS locations
with a bearing from each location...to the intersection point. I can find
one of those in my files and post it later if that is needed.

But it could been done graphically with 'Scratch-Plot' because one of the
newer features of 'Scratch-Plot' is a plot by azimuth and distance. Just
set-up a scale of UTM coordinates, plot each GPS location in UTM
coordinates, plot a line from each location with an azimuth direction and a
dummy-distance so that the lines intersect, mouse-click a point at the
intersection of the lines, and check the coordinates of the mouse-click
point immediately in the help file or later in the plot text file.

Here is a user link to 'Scratch-Plot' :

http://www.kbhscape.com/plot.htm


Also, the difference between a geodetic direction and a UTM grid direction
can be determined with 'Geodetic/UTM-Grid Utility' by entering the latitude
and longitudes and comparing geodetic directions to grid directions.

And here is a user link to 'Geodetic/UTM-Grid Utility' :

http://www.kbhscape.com/gps.htm

I have posted a law-of-cosines calculation example several times where
coordinates of an intersection point are determined from two GPS locations
with a bearing from each location...to the intersection point. I can find
one of those in my files and post it later if that is needed.


Oh, intersection of two directions is fundamentally a law-of-sines
calculation and that is a much easier calculation than a law-of-cosines
calculation. A law-of-cosines calculation is use for the intersection of two
distances...

But it could been done graphically with 'Scratch-Plot' because one of the
newer features of 'Scratch-Plot' is a plot by azimuth and distance. Just
set-up a scale of UTM coordinates, plot each GPS location in UTM
coordinates, plot a line from each location with an azimuth direction and
a dummy-distance so that the lines intersect, mouse-click a point at the
intersection of the lines, and check the coordinates of the mouse-click
point immediately in the help file or later in the plot text file.


Compass directions with declination should also be adjusted with UTM
convergence before they are used with UTM coordinates...