| Author |
Message |
Timothy Daniels
Guest
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 Posted:
Wed Sep 21, 2005 8:08 am Post subject:
Azimuth - geographic or magnetic? |
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I've noticed that there is no mention made of
magnetic deviation in all references that I've
seen to a satellite's "azimuth". Are the azimuths
given for the various DBS satellites geographic
(referenced to the earth) or magnetic (referenced
to the earth's magnetic field)?
*TimDaniels* |
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Bill Henley
Guest
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| Posted:
Wed Sep 21, 2005 8:08 am Post subject:
Re: Azimuth - geographic or magnetic? |
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Timothy Daniels wrote:
| Quote: |
I've noticed that there is no mention made of
magnetic deviation in all references that I've
seen to a satellite's "azimuth". Are the azimuths
given for the various DBS satellites geographic
(referenced to the earth) or magnetic (referenced
to the earth's magnetic field)?
*TimDaniels*
|
Azimuth shown by the receiver will be magnetic.
http://www.dbsforums.com/azel.html shows true north with a link to a map
for magnetic deviations. I've downloaded zip code to Az/El tools that
use one or the other, but those that are true north usually identify
themselves as such. It would generally be safe to assume magnetic north
and compass headings if "true" isn't mentioned. No guarantees.
--
Bill Henley |
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Bob Nielsen
Guest
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| Posted:
Wed Sep 21, 2005 8:08 am Post subject:
Re: Azimuth - geographic or magnetic? |
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Timothy Daniels wrote:
| Quote: | I've noticed that there is no mention made of
magnetic deviation in all references that I've
seen to a satellite's "azimuth". Are the azimuths
given for the various DBS satellites geographic
(referenced to the earth) or magnetic (referenced
to the earth's magnetic field)?
*TimDaniels*
|
I believe most sources of this information are geographic, but when I
had Dish network, the setup screens on the receiver used magnetic. |
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Timothy Daniels
Guest
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| Posted:
Wed Sep 21, 2005 8:08 am Post subject:
Re: Azimuth - geographic or magnetic? |
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"Timothy Daniels" wrote:
| Quote: | I've noticed that there is no mention made of
magnetic deviation in all references that I've
seen to a satellite's "azimuth". Are the azimuths
given for the various DBS satellites geographic
(referenced to the earth) or magnetic (referenced
to the earth's magnetic field)?
|
OK, forget it - I see that it's geographic. IOW
you have to know your local magnetic deviation
and combine it with the bird's geographic azimuth
to know the compass reading to look for.
*TimDaniels* |
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Bill Henley
Guest
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| Posted:
Wed Sep 21, 2005 8:08 am Post subject:
Re: Azimuth - geographic or magnetic? |
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Bob Nielsen wrote:
| Quote: |
Timothy Daniels wrote:
I've noticed that there is no mention made of
magnetic deviation in all references that I've
seen to a satellite's "azimuth". Are the azimuths
given for the various DBS satellites geographic
(referenced to the earth) or magnetic (referenced
to the earth's magnetic field)?
*TimDaniels*
I believe most sources of this information are geographic, but when I
had Dish network, the setup screens on the receiver used magnetic.
|
All of my DISH receivers have been magnetic and my DirecTV receiver
sample size is really just my next door neighber. It showed magnetic
also and I assumed other DTV receivers would as well. I guess that is
may be a bad assumption now. Neither provider promotes self installs
like they used to, but why display anything other than a compass
heading? People aren't usually going to know their deviation.
--
Bill Henley |
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Everett M. Greene
Guest
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| Posted:
Wed Sep 21, 2005 1:53 pm Post subject:
Re: Azimuth - geographic or magnetic? |
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Bill Henley <BHenley@No-Spam.CalWeb.com> writes:
| Quote: | Bob Nielsen wrote:
Timothy Daniels wrote:
I've noticed that there is no mention made of
magnetic deviation in all references that I've
seen to a satellite's "azimuth". Are the azimuths
given for the various DBS satellites geographic
(referenced to the earth) or magnetic (referenced
to the earth's magnetic field)?
*TimDaniels*
I believe most sources of this information are geographic, but when I
had Dish network, the setup screens on the receiver used magnetic.
All of my DISH receivers have been magnetic and my DirecTV receiver
sample size is really just my next door neighber. It showed magnetic
also and I assumed other DTV receivers would as well. I guess that is
may be a bad assumption now. Neither provider promotes self installs
like they used to, but why display anything other than a compass
heading? People aren't usually going to know their deviation.
|
Ask your friendly neighborhood aircraft pilot about the
deviation. S/he'll either know the answer (close enough
anyway) or can easily look it up.
OTOH, deviation is small enough in most locations as to
be insignificant for eyeball angular operations as when
installing a dish. |
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Bill Henley
Guest
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| Posted:
Wed Sep 21, 2005 4:08 pm Post subject:
Re: Azimuth - geographic or magnetic? |
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"Everett M. Greene" wrote:
| Quote: |
Bill Henley <BHenley@No-Spam.CalWeb.com> writes:
Bob Nielsen wrote:
Timothy Daniels wrote:
I've noticed that there is no mention made of
magnetic deviation in all references that I've
seen to a satellite's "azimuth". Are the azimuths
given for the various DBS satellites geographic
(referenced to the earth) or magnetic (referenced
to the earth's magnetic field)?
*TimDaniels*
I believe most sources of this information are geographic, but when I
had Dish network, the setup screens on the receiver used magnetic.
All of my DISH receivers have been magnetic and my DirecTV receiver
sample size is really just my next door neighber. It showed magnetic
also and I assumed other DTV receivers would as well. I guess that is
may be a bad assumption now. Neither provider promotes self installs
like they used to, but why display anything other than a compass
heading? People aren't usually going to know their deviation.
Ask your friendly neighborhood aircraft pilot about the
deviation. S/he'll either know the answer (close enough
anyway) or can easily look it up.
OTOH, deviation is small enough in most locations as to
be insignificant for eyeball angular operations as when
installing a dish.
|
It makes sense for a pilot to know the deviation since it changes as
they fly. And the consequences for being off are much greater<G>. It
makes no sense for a receiver to display true north Azimuth. If a
receiver displayed a true north 180° Az, that would appear on my compass
(west coast) as 166° but 196° in Boston. Either user would be off 16°
to start with.
If some DirecTV receivers display a different Az for a single slot 101
than the magnetic Az shown at
http://www.directv.com/DTVAPP/DishPointerServlet it is just subtraction
to determine your magnetic deviation. The DISH site
<http://www.dishnetwork.com/content/products/installation/azimuth/index.shtml>
displays the same magnetic Az as the receivers but the display is for a
dual sat dish. You'd have to average the 110° and 119° Az values at
DBSforums calculator to compare with the DISH site "calculator" (which
is just a table based on the 1st three digits of the ZIP code).
Asking a pilot might be easier, but I don't understand why someone
installing their dish should ever need to know the deviation. The
receiver should display magnetic in the first place.
--
Bill Henley |
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Bob Nielsen
Guest
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| Posted:
Wed Sep 21, 2005 9:29 pm Post subject:
Re: Azimuth - geographic or magnetic? |
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Everett M. Greene wrote:
| Quote: | Bill Henley <BHenley@No-Spam.CalWeb.com> writes:
Bob Nielsen wrote:
Timothy Daniels wrote:
I've noticed that there is no mention made of
magnetic deviation in all references that I've
seen to a satellite's "azimuth". Are the azimuths
given for the various DBS satellites geographic
(referenced to the earth) or magnetic (referenced
to the earth's magnetic field)?
*TimDaniels*
I believe most sources of this information are geographic, but when I
had Dish network, the setup screens on the receiver used magnetic.
All of my DISH receivers have been magnetic and my DirecTV receiver
sample size is really just my next door neighber. It showed magnetic
also and I assumed other DTV receivers would as well. I guess that is
may be a bad assumption now. Neither provider promotes self installs
like they used to, but why display anything other than a compass
heading? People aren't usually going to know their deviation.
Ask your friendly neighborhood aircraft pilot about the
deviation. S/he'll either know the answer (close enough
anyway) or can easily look it up.
OTOH, deviation is small enough in most locations as to
be insignificant for eyeball angular operations as when
installing a dish.
|
For many places that is is close enough, but there are exceptions. I
live near Seattle and the deviation is about 20 degrees. Parts of
Canada are much higher. See
<http://www.geo-orbit.org/sizepgs/magmapsp.html>. |
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slunky
Guest
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| Posted:
Thu Nov 10, 2005 9:29 pm Post subject:
Re: Azimuth - geographic or magnetic? |
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_/At 2005-11-10, Total <tbd@brain.org> wrote_
The azimuth that appears on your screen during setup is determined by
zipcode and is related to magnetic north.
--
-slunky |
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Total Brain Delete
Guest
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| Posted:
Fri Nov 11, 2005 1:08 am Post subject:
Re: Azimuth - geographic or magnetic? |
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| Quote: | It makes sense for a pilot to know the deviation since it changes as
they fly. And the consequences for being off are much greater<G>. It
makes no sense for a receiver to display true north Azimuth. If a
receiver displayed a true north 180° Az, that would appear on my compass
(west coast) as 166° but 196° in Boston. Either user would be off 16°
to start with.
|
the person on the west coast would be off by 14° |
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