Discussion:
DoD restrictions on GPS units
(too old to reply)
David Harper
2004-09-16 13:04:37 UTC
Permalink
I'm curious as to the EXACT DoD restriction on civilian GPS units
regarding speed and altitude. I'm aware that the restrictions are for
speeds >1000kts AND altitudes >60,000 ft. However, I've heard
conflicting information that the 1000kts speed restriction only
applies to the horizontal direction (ex. a rocket going straight up at
1400kts and 70,000 ft might not be restricted).

This would make sense if the primary purpose of the units is to
prevent foreign governments or "groups of malcontent" from using
civilian GPS units in their own missile technology, which would
require a higher groundspeed velocity to strike other targets.

Thanks in advance for any insight!
Dave
Sam Wormley
2004-09-16 13:34:11 UTC
Permalink
Post by David Harper
I'm curious as to the EXACT DoD restriction on civilian GPS units
regarding speed and altitude. I'm aware that the restrictions are for
speeds >1000kts AND altitudes >60,000 ft. However, I've heard
conflicting information that the 1000kts speed restriction only
applies to the horizontal direction (ex. a rocket going straight up at
1400kts and 70,000 ft might not be restricted).
This would make sense if the primary purpose of the units is to
prevent foreign governments or "groups of malcontent" from using
civilian GPS units in their own missile technology, which would
require a higher groundspeed velocity to strike other targets.
Thanks in advance for any insight!
Dave
The velocity restriction is 3D limiting use for military weapons.
Doug McDonald
2004-09-16 14:45:16 UTC
Permalink
Post by Sam Wormley
The velocity restriction is 3D limiting use for military weapons.
Is this not easily gotten around by buying from sources not
under the control of the US government?

Does not one assume that our enemies have suitable
chips, and that the larger enemies have full use of the
military capabilities of the system, easily obtained by the
spies which we know pervade our military?

Doug McDonald
Sam Wormley
2004-09-16 14:56:21 UTC
Permalink
Post by Doug McDonald
Post by Sam Wormley
The velocity restriction is 3D limiting use for military weapons.
Is this not easily gotten around by buying from sources not
under the control of the US government?
Does not one assume that our enemies have suitable
chips, and that the larger enemies have full use of the
military capabilities of the system, easily obtained by the
spies which we know pervade our military?
Doug McDonald
And anybody can make their own GPS receivers... Selling those
capable chips away is not in the best interest of the US military.
Doug McDonald
2004-09-16 16:05:56 UTC
Permalink
Sam Wormley wrote:
\
Post by Sam Wormley
Post by Doug McDonald
Does not one assume that our enemies have suitable
chips, and that the larger enemies have full use of the
military capabilities of the system, easily obtained by the
spies which we know pervade our military?
Doug McDonald
And anybody can make their own GPS receivers... Selling those
capable chips away is not in the best interest of the US military.
You post is not parseable.

What I am saying is that any "significant" enemy such
as Russia, China, India, France, etc., perhaps Pakistan,
would have spies who would get either the plans or specs
or sample of military capable chips, which would then
be locally made.

Doug McDonald
Joop van der Velden
2004-09-17 05:29:04 UTC
Permalink
Post by Doug McDonald
You post is not parseable.
What I am saying is that any "significant" enemy such
as Russia, China, India, France, etc., perhaps Pakistan,
I wonder what makes you put France in this line of "significant" US
enemy's.
--
Joop van der Velden - ***@amsat.org
Jon Parmet
2004-09-17 14:27:30 UTC
Permalink
Post by Doug McDonald
Post by Sam Wormley
Post by Doug McDonald
Does not one assume that our enemies have suitable
chips, and that the larger enemies have full use of the
military capabilities of the system, easily obtained by the
spies which we know pervade our military?
Doug McDonald
And anybody can make their own GPS receivers... Selling those
capable chips away is not in the best interest of the US military.
You post is not parseable.
Check you ;) parser. It made sense to me.
Post by Doug McDonald
What I am saying is that any "significant" enemy such
as Russia, China, India, France, etc., perhaps Pakistan,
would have spies who would get either the plans or specs
or sample of military capable chips, which would then
be locally made.
Doug McDonald
There's more to PPS than just having the chip/spec. You're reaching.


Regards,
Jon
David Harper
2004-09-16 18:53:05 UTC
Permalink
Post by Sam Wormley
The velocity restriction is 3D limiting use for military weapons.
That's what I originally THOUGHT, but I contacted Garmin about the DoD
restriction about reaquisition time after exceeding the DoD limitation
on speed over 60k ft (and then slowing down). I was given the
following reply:

"The restriction (imposed by the DOD) of horizontal velocity over
60,000 feet
will take effect. There will be no position reporting during that
power
cycle."

I noted the word 'horizontal'. So I says:
"If I understand your answer correctly, I could be at 120,000ft with a
vertical velocity of 1100kts and a horizontal velocity of 200kts, and
the GPS unit would still output position data, and would be free of
the DoD restriction. Is this statement correct?"

And him says:
"Sir, as I asked the OEM sales Rep. As he described it, it was only
for
horizontal velocity. He did not indicate the same for vertical
velocity. I
will try to get in touch with him again. I do believe your statement
to be
correct. Let me make sure that I understood the restriction
correctly."

And after a day, I get confirmation. He spoketh:
"Sir, the answer is that vertical velocity does not apply. GPS main
function
is for horizontal velocity."

So I'm wondering if it is a common misconception that the velocity
restriction is 3D, or if the guy at Garmin was smoking crack...?


Dave
Bad Idea
2004-09-17 01:20:07 UTC
Permalink
Just curious, did you ask how many angels can dance on the head of a pin?
David Harper
2004-09-17 12:30:27 UTC
Permalink
Post by Bad Idea
Just curious, did you ask how many angels can dance on the head of a pin?
Seeing as how sounding rockets easily exceed 60,000 ft and 1000kts
(vertically, but not horizontally)... no.
Noel Bachelor
2004-09-19 04:37:27 UTC
Permalink
Post by David Harper
"Sir, the answer is that vertical velocity does not apply. GPS main
function
is for horizontal velocity."
So I'm wondering if it is a common misconception that the velocity
restriction is 3D, or if the guy at Garmin was smoking crack...?
It has often been mentioned here that they only use the horizontal
component for distance and speed display etc, so going uphill or down dale
is still only measured as the distance or speed sideways. It makes sense
then that the velocity restriction would only be applied hoizontally as
well.


Noel Bachelor noelbachelorAT(From:_domain)
S 12.416980
E130.922680
David Harper
2004-09-19 12:31:58 UTC
Permalink
Post by Noel Bachelor
Post by David Harper
"Sir, the answer is that vertical velocity does not apply. GPS main
function
is for horizontal velocity."
So I'm wondering if it is a common misconception that the velocity
restriction is 3D, or if the guy at Garmin was smoking crack...?
It has often been mentioned here that they only use the horizontal
component for distance and speed display etc, so going uphill or down dale
is still only measured as the distance or speed sideways. It makes sense
then that the velocity restriction would only be applied hoizontally as
well.
I looked at some of the Garmin specs and NMEA approved sentences (as
well as the Garmin sentences) and none of them addressed vertical
velocity, with the one exception of the text output. However, it's
units are meters/sec, and is in the format mm.mm, so it can't read
higher than 99.99 m/s. I would figure that you're right, and the unit
is not limited by vertical velocity because it doesn't really
calculate that directly. Technically you could determine
delta-z/time...

Dave
L***@OverThere.edu
2014-09-10 21:20:58 UTC
Permalink
Noel,

Could you please provide some NMEA data for me to test a program with.
I need some southern hemisphere sentences.

You could post a few minutes worth here or email it to me. An hour
would be really nice. "mikey" at "ILikeTheInternet" dot goes here
"com". Not sure why I bother disguising the address. I get so much
SPAM already!

It is a free program so this is not a commercial venture. Source and
compiled versions posted. The program will write the data I need.
NMEAgent from ILikeTheInternet.com. VB6 Source at
PlanetSourceCode.com or by request.

Thanks for any help with this,
Mike
Post by Noel Bachelor
Post by David Harper
"Sir, the answer is that vertical velocity does not apply. GPS main
function
is for horizontal velocity."
So I'm wondering if it is a common misconception that the velocity
restriction is 3D, or if the guy at Garmin was smoking crack...?
It has often been mentioned here that they only use the horizontal
component for distance and speed display etc, so going uphill or down dale
is still only measured as the distance or speed sideways. It makes sense
then that the velocity restriction would only be applied hoizontally as
well.
Noel Bachelor noelbachelorAT(From:_domain)
S 12.416980
E130.922680
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