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<font face="Arial">The Z axis reading is high relative to the Z axis
value of 48,032.0nT from the World Magnetic Model for that day for
my specific location of 42deg 15min 41.24sec North, 73deg 32min
32.43sec West, 1220 ft elevation. <br>
<br>
Hyomin, have you had time to complete the solenoid coil
measurement of the RM3100?<br>
<br>
Jules - K2KGJ<br>
<br>
</font><br>
<div class="moz-cite-prefix">On 9/15/2020 11:58 AM, Kim, Hyomin
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAFXoXAW7OLzRLhYjzGhokM56XNEWUjn1xDQOeeuuvfS-0ESOAA@mail.gmail.com">
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<div dir="ltr">Just to add to Phil's comments, what I see from the
Z axis (if I am not wrong), is that there is a drift (whether
real or not) in our Z axis data: for example, Bz in the USGS mag
began at ~0 nT and ended at ~0 nT whereas ours began at ~49980
nT and ended at 50000 nT, which is a 20 nT increase.
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style="color:rgb(111,111,111);font-size:13px">Hyomin Kim</strong><br>
<font color="#6f6f6f">Assistant
Professor</font><br>
<font color="#6f6f6f">Physics<br>
</font><font color="#666666">Center
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<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Sep 15, 2020 at 11:53
AM Phil Erickson <<a href="mailto:phil.erickson@gmail.com"
moz-do-not-send="true">phil.erickson@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Hi David,
<div><br>
</div>
<div> When I say "secular change", I meant the time scale
of the change. Secular = long term, in this case relative
to the time scales of a magnetic disturbance. For
example, storm time current variations might occur on a
few minute to hour or two scale, but would not last for 24
hours. The latter is what I was referring to and
indicates a more long term drift. If you saw that drift
for example from day to day, that is now climatology (not
weather) and you would have to see whether that is
reasonable geophysically.</div>
<div><br>
</div>
<div>73</div>
<div>Phil</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Sep 15, 2020 at
11:50 AM David Witten <<a
href="mailto:wittend@wwrinc.com" target="_blank"
moz-do-not-send="true">wittend@wwrinc.com</a>> wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Phil, Hyomin,
<div><br>
</div>
<div>I believe that I understand your comments, but to
be sure, may I ask exactly what is meant by 'secular
change'. I do not want to make incorrect assumptions
about a term of art.</div>
<div><br>
</div>
<div>Dave</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Sep 15, 2020
at 10:45 AM Phil Erickson <<a
href="mailto:phil.erickson@gmail.com"
target="_blank" moz-do-not-send="true">phil.erickson@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px
0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">If it is picking up a 10 nT level
secular change, that is fabulous for a reasonable
cost sensor! Maybe Jules has a ground induced
current nearby? Anyhow, temperature sensitivity at
a more precise level is I'm sure all part of the
calibration needs, so we'll find out later...
<div><br>
</div>
<div>Phil</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Sep 15,
2020 at 11:40 AM Kim, Hyomin <<a
href="mailto:hmkim@njit.edu" target="_blank"
moz-do-not-send="true">hmkim@njit.edu</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px
0px 0px 0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Ah, yes I agree - the secular
change seems to be a little off. I paid more
attention to the small scale variations which
look to be similar. This is a mystery to me.
Maybe our sensor is not so precisely calibrated,
say, to ambient temperature or something? Or we
found another magnetic anomaly near where Jules
lives!!
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<font
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href="https://web.njit.edu/~hmkim/"
target="_blank" moz-do-not-send="true">https://web.njit.edu/~hmkim/</a><br>
104 Tiernan
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<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Sep
15, 2020 at 11:34 AM Phil Erickson <<a
href="mailto:phil.erickson@gmail.com"
target="_blank" moz-do-not-send="true">phil.erickson@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Hi Hyomin,
<div><br>
</div>
<div> You have a more expert eye than I do,
so I read your statements as "uncalibrated
axes", which of course is entirely correct
for this RM3100 data. I just don't know
how to separate the geophysical
(latitudinal difference) from the
instrumental (positional axes are not
exactly the same). I was reacting mostly
to the 24 hour secular change in each
component. Is it reasonable to assume
that is much less sensitive for horizontal
vs vertical components?</div>
<div><br>
</div>
<div>73</div>
<div>Phil</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue,
Sep 15, 2020 at 11:27 AM Kim, Hyomin <<a
href="mailto:hmkim@njit.edu"
target="_blank" moz-do-not-send="true">hmkim@njit.edu</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Hi Phil,
<div>At a first glance I thought the Z
traces matched well as the relative
values appear to be similar in that
axis. If I am not wrong, Bz is
oriented toward the center of the
earth for the USGS mags. I believe the
USGS mag is quite precisely oriented
whereas our mag is not. Thus any
slight offset in orientation can be
seen noticeably as Bz has the biggest
values? Also, the latitudinal
difference between his place and
Fredericksburg could be another
factor? </div>
<div><br>
</div>
<div>Hyomin</div>
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style="color:rgb(111,111,111);font-size:13px">Hyomin Kim</strong><br>
<font
color="#6f6f6f">Assistant
Professor</font><br>
<font
color="#6f6f6f">Physics<br>
</font><font
color="#666666">Center
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href="https://web.njit.edu/~hmkim/"
target="_blank" moz-do-not-send="true">https://web.njit.edu/~hmkim/</a><br>
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<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On
Tue, Sep 15, 2020 at 10:39 AM Phil
Erickson via TangerineSDR <<a
href="mailto:tangerinesdr@lists.tapr.org"
target="_blank"
moz-do-not-send="true">tangerinesdr@lists.tapr.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Hi Dave,
<div><br>
</div>
<div> The X and Y traces return
after 24 hours to nearly the same
relative value in both the
reference and RM3100 traces. The
Z trace does not. Ionospheric
currents flowing in the E region
should not affect Z exclusive of X
and Y under most any geometry I
can think of, so I wondered
whether the uncalibrated RM3100
was likely causing this. (I have
never professionally calibrated a
magnetometer, so Hyomin might need
to comment here.). In other words,
I always assume there is some
measurement systematic until it
has been completely ruled out
before assigning it to geophysical
variation.</div>
<div><br>
</div>
<div>73<br>
</div>
<div>Phil W1PJE</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On
Tue, Sep 15, 2020 at 10:34 AM
David Witten <<a
href="mailto:wittend@wwrinc.com"
target="_blank"
moz-do-not-send="true">wittend@wwrinc.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">@Phil,
<div><br>
</div>
<div>Correlation is great, and
surely some further
calibration issues may
remain. But these sensors are
NOT colocated - (200-300+ mi
apart?) . Wouldn't it be
suspicious if they did
correlate perfectly? If they
did, shouldn't we ask if we
do really need an extensive
array of these sensors?
Presumably there will always
be some local variation at
this scale? (don't know, just
asking)<br>
</div>
<div><br>
</div>
<div>Dave Witten, KD0EAG</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr"
class="gmail_attr">On Tue, Sep
15, 2020 at 7:21 AM Phil
Erickson <<a
href="mailto:phil.erickson@gmail.com"
target="_blank"
moz-do-not-send="true">phil.erickson@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Hi all,<br>
<div><br>
</div>
<div> There appears to be a
10 nT drift in the Z
component for the RM3100
that is not in the
Fredericksburg traces. Is
that slow systematic bias
expected? Maybe things
are not calbrated over
that time frame quite yet?</div>
<div><br>
</div>
<div>73</div>
<div>Phil W1PJE</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr"
class="gmail_attr">On Mon,
Sep 14, 2020 at 10:49 PM
David Witten via
TangerineSDR <<a
href="mailto:tangerinesdr@lists.tapr.org"
target="_blank"
moz-do-not-send="true">tangerinesdr@lists.tapr.org</a>>
wrote:<br>
</div>
<blockquote
class="gmail_quote"
style="margin:0px 0px 0px
0.8ex;border-left:1px
solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">I don't
believe that my previous
post carried the file
K2KGJ provided.<br>
<br>
<div class="gmail_quote">
<div dir="ltr"
class="gmail_attr">----------
Forwarded message
---------<br>
From: <strong
class="gmail_sendername"
dir="auto">Julius
Madey</strong> <span
dir="auto"><<a
href="mailto:hillfox@fairpoint.net" target="_blank"
moz-do-not-send="true">hillfox@fairpoint.net</a>></span><br>
Date: Mon, Sep 14,
2020 at 4:26 PM<br>
Subject: another
24hour RM3100 run
and comparison with
Fredericksburg<br>
To: Kim, Hyomin <<a
href="mailto:hmkim@njit.edu" target="_blank" moz-do-not-send="true">hmkim@njit.edu</a>>,
David Witten <<a
href="mailto:wittend@wwrinc.com" target="_blank" moz-do-not-send="true">wittend@wwrinc.com</a>>,
Dr. Nathaniel A.
Frissell Ph.D. <<a
href="mailto:nathaniel.frissell@scranton.edu" target="_blank"
moz-do-not-send="true">nathaniel.frissell@scranton.edu</a>>,
Dave Larsen <<a
href="mailto:kv0s.dave@gmail.com"
target="_blank"
moz-do-not-send="true">kv0s.dave@gmail.com</a>><br>
</div>
<br>
<br>
<div> <font
face="Arial">All,
<br>
I was hoping to
record a
relatively short
term event but
missed one about
10 days ago.
However, there was
a good run on the
12th with an ~30nT
excursion on the Y
axis lasting about
an hour. In the
attached pdf, the
three axes of the
RM3100 again track
the Fredericksburg
magnetometer
station data quite
closely. The
RM3100 plotted
data points are
simple running
60second averages
and not the more
complex filtering
algorithm used by
Intermagnet
stations for their
1 minute data
points. <br>
<br>
The vertical axes
scales on all
plots are as close
as I could match
them by eye in
cutting and
pasting.<br>
<br>
I believe the
value to the right
on the Intermagnet
plot is the mean
for the 24 hour
period. I did not
try to compute a
24 hour mean.<br>
<br>
One of the
products for the
future for general
interest would be
a running plot
like those
available on
Intermagnet.org.
I guess we can
dream a bit. <br>
<br>
Jules - K2KGJ<br>
</font> </div>
</div>
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<div dir="ltr">----<br>
Phil Erickson<br>
<a
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-- <br>
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Phil Erickson<br>
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target="_blank" moz-do-not-send="true">phil.erickson@gmail.com</a><br>
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-- <br>
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Phil Erickson<br>
<a href="mailto:phil.erickson@gmail.com" target="_blank"
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